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  • richardmitnick 1:30 pm on February 16, 2018 Permalink | Reply
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    From ESOblog: “How to Install a Planetarium A conversation with engineer Max Rößner about his work on the ESO Supernova” 

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    ESOblog

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    Part of ESO Headquarters in Garching, Germany, is currently in a frenzy of activity as we prepare to open the ESO Supernova Planetarium & Visitor Centre in April 2018. This cutting-edge free astronomy centre is equipped with a 14-metre planetarium dome and an amazing exhibition that takes visitors on a journey to the stars. It’s a lot of work to install a planetarium system from scratch, but to engineer Max Rößner, the ESO Supernova is like a giant playground.

    ESO Supernova Planetarium, Garching Germany

    Q: What’s your role at the ESO Supernova Planetarium & Visitor Centre?

    A: I’d say that I am the Systems Engineer for the ESO Supernova planetarium. I concentrate on the technical implementation of the planetarium, integrating the projection and multimedia systems. Sometimes I also work on the content — such as the shows and night sky tours that will be played on the dome. There is quite a lot of pressure, as at the moment I am the only person who entirely understands the planetarium system, so in a way the project depends on me.

    Q: How do you know so much about planetariums?

    A: I’ve been working in planetariums for most of my life. I started presenting planetarium shows when I was about 10 or 11 in a small planetarium near Augsburg, which is about an hour from Munich, Germany. It is run by an association of volunteers and it was my first taste of these magical places. Of course in the beginning I worked in a voluntary capacity, but it also helps now that I am an engineer.

    Q: How is the ESO Supernova’s planetarium different to those you have previously worked in?

    A: It’s very different. The most obvious visible difference is that the ESO Supernova has an inclined dome — it is tilted by 25 degrees to allow for a better viewing experience. Overall, it’s a complex project, because we are actually implementing two different planetarium systems from Zeiss and Evans & Sutherland (E&S). The market of planetarium systems is a packed field, including Zeiss, E&S, and numerous others. All of them have their pros and cons. Our system looks a lot like a DJ deck — we have an audio mixer, spotlights, and lots of effects!

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    Max Rößner at the control board of the newly installed planetarium at the ESO Supernova Planetarium & Visitor Centre.
    Credit: ESO

    Another difference is that the ESO Supernova won’t use an optomechanical projector, usually used to project a nice starry sky. Instead, we are using a digital projection. Both types have positives and negatives. Optomechanical projectors are better at creating really precise stars — tiny, exact pinpricks of light. However, with the digital projection system there is much greater flexibility, and a much greater range in what we can show. For example, the presenter can even fly to a different location in space, which can’t be done with an optomechanical projector.

    Q: What kind of experience are you aiming to give visitors with these awesome systems?

    A: There is a joke in the planetarium world that people go to planetariums twice in their life: as a child and with their children. In the past, presenters generally gave a tour of the starry sky, including the Big Dipper and other famous constellations, and they would also point out some planets. But to match the expectations of audiences today, we use more advanced technology to create the kinds of shows that can also be continually updated to match modern science, and that are more personal and changeable.

    We want to avoid presenting a Hollywood-style film that has a clear beginning and neatly wrapped-up ending, so visitors just come, watch it and leave. Instead we want to create a dialogue with the audience, presenting each show with a more personal flair so each one is different. This can evolve depending on who is in the audience — such as their age or their background — and the questions people have throughout the show can also influence its direction.

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    The ESO Science Outreach Network (ESON) visited the ESO Supernova in 2017 and had a sneak-peek of some of the delights to come, learning more about the Extremely Large Telescope (ELT) on a test fulldome show. Credit: ESO/P. Horálek

    Q: You mentioned that the dome is tilted — why?

    A: This is a philosophical question. A tilted planetarium dome does make it a little more difficult to orient the audience, as people are used to using the Earth’s horizon as a reference point for celestial objects. For example, it is a little harder to demonstrate that the Sun rises in the east and sets in the west, because the sky itself isn’t tilted! But with the planetarium seats, which are raised up ‘diagonally’ on a slope like cinema seats, your brain does seem to correct for this.

    An advantage of the tilted dome is that people don’t have to look up very far, so they can look at the dome in a comfortable way and feel fully immersed in the show.

    A: There are a few technical and practical reasons for this:

    Ventilation: Fresh air comes in and used air goes out.
    Noise: We want the sound from within the planetarium to penetrate through the dome rather than bouncing off it completely, or we would end up with a chaotic chamber of echoing noise. The loudspeakers are also mounted behind the dome, and the sound needs to get through so we can hear it.
    Reflections: Similar to the problem of noise, we don’t want light to reflect around the dome from one area to another. The holes and the paint give the dome 58% reflectivity, reducing this problem.

    Q: How is content made differently for the curved screen of the planetarium?

    A: There are two ways to develop content for a planetarium. Firstly, to create films with a fisheye-like representation so they display correctly on the dome. In order to achieve this, a film is first split into the various projection fields, and then warped to compensate for the curved nature of the dome. These little pieces of the frame are then stored on individual PCs and fed to the different projectors.

    Live shows are another type of content. They are created and rendered on the spot, at the moment you present them. For example, we can show the sky as the visitors would see it now, outside. Tomorrow the Moon will change its position a little, and the Sun will set a bit later as we head towards spring, so we can adjust for these changes every day. This is a native functionality of Digistar, which is the planetarium system created by E&S. It’s a little like Google Maps, except with time, and showing the Universe.

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    With just a few months until the opening of the ESO Supernova Planetarium & Visitor Centre in spring 2018, the interior of the Centre is coming together.
    Credit: ESO/P. Horálek

    Q: What’s the day-to-day work like in a planetarium?

    A: It’s great! I love having some freedom in making design decisions and seeing those decisions realised. It’s exciting to see something you have planned and worked on for such a long time coming into reality, and to know that you are a big part of it.

    Q: What has been the biggest challenge so far?

    A: We’ve faced so many challenges. One memorable moment was when we were trying to test the software, but nothing happened. Nothing turned on, and we just saw a black sky above us. Of course, we panicked — but it turned out that we had left the dust caps on the projectors! So luckily, that didn’t turn out to be too challenging to fix. Even specialists make mistakes!

    An actual challenge was to raise awareness about our operational requirements. For example, we had to clearly communicate to the architects that we need a low horizon, room for equipment, extra sockets, space in the server room, and so on. Essentially, we were concerned about the practical side of running a planetarium with limited manpower and how that would be balanced with the architectural priorities of design and aesthetics.

    Then there’s the pressure from the fact that the project is dependent on me, because the software is absolutely fundamental to the working of the planetarium. One of the most difficult things has been getting the two planetarium systems to work together in a unified way. We need the added computational power of the second system to realise our operational goals.

    Of course, another challenge is that funding has been a limiting factor in some ways. Any project is easier when you have boundless amounts of money, but that’s not the reality here — especially since the ESO Supernova will be a free, open-source visitor centre.

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    A striking sunset shines upon the futuristic curves of the ESO Supernova Planetarium & Visitor Centre.
    Credit: P. Horálek/ESO

    Q: Another exciting part of the ESO Supernova project is the Data2Dome system. Tell us more about that.

    A: Up until now, planetariums have struggled to present really up-to-date content. First of all the content — such as new films, video clips or images — has to be found on the internet, then downloaded, then uploaded to the planetarium system. A script then has to be written to present alongside the content. This means it can take weeks for new research findings from around the world to reach planetariums’ audiences. Other mediums are way faster, like the internet, TV, and newspapers. So there was a problem: a planetarium is meant to be the competence centre of astronomical knowledge in a community, but it was lagging behind.

    We wanted to streamline the process of bringing research from astronomers to audiences around the world. ESO’s outreach department collaborated with E&S and the International Planetarium Society to come up with a technical standard: Data2Dome.

    Essentially, this helps scientific organisations publish their content in such a way that it enables planetarium vendors to download the content directly into their software. Manually shuffling and downloading data is bypassed. NASA, ESA, ESO and many others can directly stream their content into planetariums worldwide. It’s a free and open standard, first implemented by E&S. In particular, it’s great for smaller planetariums that may not have the time to continuously create new content.

    People are already using this software around the world — Data2Dome is streaming content to planetariums as we speak.

    Q: What are you looking forward to most once the ESO Supernova opens?

    A: It will be great to have the planetarium fully working and engaging with the audience. I feel the planetarium is my brainchild, so seeing it finally come to life will be amazing.

    Q: You’ve been working in planetariums for so many years — do you still feel excited when a show begins?

    A: Of course. This space holds a certain fascination that has never left me. I still get goosebumps. Emotion is a key part of the planetarium experience: shows are not just meant to teach you, but to touch you. When you think about it, the entire known Universe is stored in the computers downstairs at the ESO Supernova…so in a small dome on the edge of a city in Germany, we can leave Earth and travel to a different part of the Universe.

    See the full article here .

    Please help promote STEM in your local schools.
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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

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  • richardmitnick 3:38 pm on February 9, 2018 Permalink | Reply
    Tags: , , , , ESOblog, Understanding How Stars Die   

    From ESOblog: “Understanding How Stars Die” 

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    ESOblog

    Markus Wittkowski on using a team of telescopes to image dying stars

    9 February 2018

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    Science@ESO

    Over the centuries, astronomers have learned that stars are not just static pinpricks of light in the sky — they are dynamic and evolving objects that go through life cycles. Stars of different sizes evolve in different ways, and many processes of stellar evolution are still poorly understood. In a recent paper that appeared in Astronomy & Astrophysics, ESO astronomer Markus Wittkowski and his team imaged a star belonging to a particular group of old stars called AGB stars. We chatted to Markus to find out more.

    Q: So what are AGB stars and why did you want to study them?

    A: AGB stars, or asymptotic giant branch stars, are low- or intermediate-mass stars like our Sun that are at the end of their lives. At this stage, these stars have become red giants — they’re cooling off, creating extended atmospheres, and they’re losing a lot of mass in a dense stellar wind. They also periodically undergo pulses — about every 10 000 to 50 000 years — which blow material off the surface of the star at a much faster rate than normal. This helps create large shells of gas and dust, and eventually, these stars become planetary nebulae.

    We have a basic idea of this mass-loss process but we don’t know many details, in particular how this mass loss is initiated close to the surface of the star. So we wanted to find out more. Different types of AGB stars, like carbon-rich or oxygen-rich stars, have different properties. The mass-loss process is theoretically best understood for carbon-rich stars, so we decided to closely study the carbon-rich AGB star R Sculptoris — and our results are the start of a detailed understanding of what happens.

    Q: What can studying AGB stars tell us about the Universe?

    A: Studying AGB stars is important to understand stellar evolution. The amount of mass lost by the star actually changes its evolution and creates different types of planetary nebulae. Understanding these processes is important because AGB stars are one of the main producers of dust in the Universe, which means they enrich the Universe with elements.

    AGB stars are one part of the element-making puzzle because in the process of their death they can produce a vast range of elements — including 50% of elements heavier than iron. These elements are blown into the Universe to make new stars, new planets, new moons…to create the building blocks of everything else. To understand the stellar evolution process, we need to understand how these elements are created and released into the Universe.

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    Astronomers captured this ghostly image of AGB star R Sculptoris using ESO’s Very Large Telescope Interferometer (VLTI). The image covers a very small section of the sky: approximately 20×20 milliarcseconds. For comparison, Jupiter has an angular size of approximately 40 arcseconds.
    Credit: ESO/M. Wittkowski (ESO)

    Q: What did you find out?

    A: We were looking specifically at the region close to the stellar surface of the AGB star R Sculptoris, which is the region where mass-loss is initiated. We found that R Sculptoris has one dominant bright spot on its stellar disc, two or three times brighter than the other regions. This contrast is very large so we wondered how to explain it. We know that these stars have large convection cells of moving gas on their surface, but these wouldn’t produce such a large contrast. Moreover, for AGB stars we expect that such detailed structure would be obscured by the extended atmosphere and dense stellar wind. Previous radio observations of R Sculptoris with the Atacama Large Millimeter/submillimeter Array (ALMA) showed an interesting spiral structure within the stellar wind much further out from the star, which hints at the presence of a previously unknown companion star, cutting through the dust as it orbits. However, the distance to this companion is too large to cause the structure close to the surface of R Sculptoris that we observed.

    We compared our results to atmosphere and wind models, which predict that these convection cells on the photosphere are also related to mass loss and dust formation. This means that large convection cells with low contrast will lead to asymmetric dust formation — we’d get big blobs of dust forming, instead of a spherical dusty shell. This helped us to interpret our results: we realised we were seeing dust two or three stellar radii out from the star’s surface, forming not uniformly but in large clumps. The bright spot we saw is actually a spot where there is little to no dust, and we can look deeper into the stellar surface, where it’s brighter. The remaining parts appear darker because the starlight is blocked by the forming dust. Our “bright” spot is not actually inherently brighter, it’s simply a region that is less obscured by dust!

    Q: What makes R Sculptoris interesting to study?

    A: First of all, there aren’t many known carbon-rich AGB stars. We also needed to use a star that has the right size and the right brightness to observe it. As I mentioned, ALMA has previously found a spiral structure around R Sculptoris, which reveals a mass-loss history at much larger distances — the star had already thrown off large amounts of dust and transported it out to large distances.

    The spiral gives us a lot of information about the mass loss history, including how the mass was lost, at which rate, and at what velocity. The observations we took using the Very Large Telescope Interferometer (VLTI) are complementary to the ALMA observations. They show us the present state of the star because we can look directly at the part of the star where the dust forms, very close to the stellar surface. That’s too close for ALMA, which can only see the spiral of dust that occurs at distances a dozen of time larger.

    I also find the technique we used very exciting because we can use it to see the surface of stars, which until very recently we could only do for our own Sun.

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    ALMA observations revealed an unexpected spiral structure in the material around the old star R Sculptoris, probably caused by a hidden companion star orbiting the star.
    Credit: ALMA (ESO/NAOJ/NRAO)/M. Maercker et al.

    Q: Tell us more about the technique you used to make your observations.

    A: We used interferometric imaging to look at R Sculptoris. Imagine if you drop a stone into a lake and it makes a pattern of ripples radiating out through the water. Then you drop a second stone into a lake, which will create a second pattern, and the two will interfere at some point. This interference is what we’re interested in.

    Optical interferometry is like the double slit experiment that people do in high school physics, where you combine two beams coming from the same light source and look at the interference pattern produced. In interferometry at the Very Large Telescope, we combine light from different telescopes — sometimes up to a hundred metres apart — and it gives us a higher spatial resolution. It’s like observing a star with a 100-metre telescope. The resultant interference gives us information on very small spatial scales. If we combine a lot of these observations, we can actually reconstruct the image of the star.

    Interferometry is not an easy technique, but recent advances in observation efficiency and precision, as well as image-reconstruction techniques, allow us now to image stars other than the Sun. We tried several image-reconstruction methods and they all gave the same results, so we are quite confident that the images we reconstructed are correct.

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    Inside the tunnels housing instruments for the Very Large Telescope Interferometer (VLTI)
    Credit: ESO

    Q: Why do you need this technique to study these stars?

    A: Usually, if you look at a star with a single telescope, it’s so small that it appears to be a single point. From a single telescope, anything smaller than 30 to 60 milliarcseconds can’t be resolved. Astronomers use arcseconds to measure the angular sizes of objects on the sky; the Moon, for example, is around 30 arcminutes or 1800 arcseconds. Most stars are smaller than 30 to 60 milliarcseconds — R Sculptoris, for example, has an angular size of about 10 milliarcseconds, so it’s much smaller than what we could resolve with one telescope alone. But if we use interferometry to combine the observations of multiple telescopes, we can dramatically increase the resolution we can obtain! With the VLTI and its PIONIER instrument, we have observed scales of one or two milliarcseconds, so we can look at the details on the surface of the star.

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    One of the VLT’s Auxiliary Telescopes (AT) looks up at the stars of the Milky Way
    Credit: ESO/José Francisco Salgado (josefrancisco.org)

    Q: What’s next in this area of research?

    A: My colleagues and I are so excited about these imaging results coming out — not only for R Sculptoris but also for other similar stars, such as red giants and red supergiants, some with less dust around them. We’re getting a lot of new results in a lot of different wavelengths for more stars. We are now at a point where we can obtain resolved images of a variety of stars, so that’s quite exciting.

    We’re planning a workshop at ESO to discuss these results and put them all together. It’s a very exciting time at the moment because we can finally produce these images at different wavelengths. The models I mentioned are also progressing thanks to advances in computing power — we can now calculate and simulate the environment around a star, including the dust formation, in three-dimensions! You can see these clumps of dust in the models too, which is relatively new. So it’s a very exciting moment to bring all of these results together and plan the next steps.

    See the full article here .

    Please help promote STEM in your local schools.
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    Visit ESO in Social Media-

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

     
  • richardmitnick 9:54 pm on February 2, 2018 Permalink | Reply
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    From ESOblog: “Little Galaxies, Big Mysteries” 

    ESO 50 Large

    ESOblog

    2 February 2018

    1
    Science@ESO

    In order to understand some of the weirdest and most wonderful phenomena in the Universe, scientists rely on the Lambda Cold Dark Matter (LCDM) model. This model assumes the existence of dark matter and dark energy to explain things like the cosmic microwave background, the structure of galaxies, the abundances of elements and the accelerating expansion of the Universe. But recent research hints that this model might not explain everything. Astronomers have found a plane of dwarf galaxies orbiting Centaurus A, one of our closest galaxies — a discovery that challenges the long-held LCDM model. One of the team members is ESO astronomer Federico Lelli, so we chatted with him to find out more.

    Q: Firstly, what is a dwarf galaxy and why did you want to study them?

    A: Dwarf galaxies are the most numerous and most common types of galaxies in the Universe, but they are smaller and less massive than galaxies like our own Milky Way. The Milky Way, for example, contains about 100 billion stars, while dwarf galaxies may contain anywhere from a few thousand to “only” a billion stars. One famous example of a dwarf galaxy is the Small Magellanic Cloud, which is visible to the naked eye from the Southern Hemisphere. Dwarf galaxies are important in many aspects of astronomy, but to me they are particularly interesting because they can be used to test the currently most popular cosmological model, the Lambda Cold Dark Matter (LCDM) model, in which the mysterious dark matter and dark energy constitute more than 95% of the total mass-energy budget of the Universe.

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    An image from the Millennium-II Simulation, showing a central dark matter halo hosting a large galaxy, plus the surrounding dwarf galaxies.
    Credit: Boylan-Kolchin et al. (2009)

    Q: How can dwarf galaxies test the cosmological model?

    A: First of all, dwarf galaxies are thought to be heavily dominated by dark matter because they show large mass discrepancies. Let me explain what that means. By studying the motions of stars and gas within dwarf galaxies and using Newton’s gravitational law, we can estimate their total mass. But when we compare this number to the actual mass we see in stars and gas, the two numbers are vastly different — by a large factor, from tens to thousands depending on the object. We interpret this as evidence for large amounts of unseen dark matter inside dwarf galaxies. These galaxies are therefore prime natural laboratories to test different dark matter models or alternative gravity theories.

    Over the past ten years, however, people realised that we can also test our current cosmological model by looking at the distribution of dwarf satellites around their “host” galaxies and comparing that with the prediction of computer simulations based on the LCDM model.

    Q: Can you explain in more detail how this is done?

    A: According to the LCDM model, galaxies form at the centres of halos of dark matter. Using supercomputers, theoreticians can simulate the formation and growth of dark matter halos over time, from the Big Bang to the present day. It turns out that massive dark matter halos, which host bright galaxies, are generally surrounded by many smaller dark matter halos, which should host dwarf galaxies. The small halos are distributed in a random, nearly spherical fashion around the big one and move in a chaotic way, like bees around a hive. This is a neat prediction that can be tested by actually looking at the motions and positions of dwarf galaxies out in the Universe.

    Q: Have other researchers looked at this before?

    A: Sure, and the first results raised a big scientific debate. Arguably, the best-studied galaxies in the Universe are the Milky Way and its big neighbour, the Andromeda Galaxy. Both galaxies are surrounded by several dwarf satellites. But early research realised that these dwarfs are not distributed in a random way, as predicted by cosmological simulations. It was found that the satellites of the Milky Way lie in a narrow plane, which is perpendicular to the Milky Way’s disc, and they also seem to rotate within this plane — sort of like the planets around the Sun, except the orbits of dwarf galaxies are way more complex and uncertain. Imagine a pancake-like disc of dwarf galaxies, spinning around the Milky Way.

    Co-rotating planes of satellite galaxies are rare in cosmological simulations, occurring in less than 1% of simulated central dark matter halos, so people naturally thought that the Milky Way must be a bit of a weirdo. It was later discovered that the Andromeda Galaxy also hosts a plane of satellites, making this galaxy just as much of a weirdo as our own. At this point, people started to wonder whether the cosmological predictions are actually correct, or whether the Local Group of galaxies — including the Milky Way and the Andromeda Galaxy — is atypical and shouldn’t be used to test cosmology.

    Local Group. Andrew Z. Colvin 3 March 2011

    Q: How have you and your collaborators tried to answer these questions?

    A: We decided to look at satellite galaxies outside the Local Group to test whether the Milky Way and Andromeda are indeed atypical. We started with Centaurus A (also known as Cen A), which is a big elliptical galaxy in the constellation of Centaurus, about 13 million light-years away.

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    Centaurus A (NGC 5128)
    Date 28 January 2009
    Source http://www.eso.org/public/images/eso0903a/
    Author ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)

    Colour composite image of Centaurus A, revealing the lobes and jets emanating from the active galaxy’s central black hole. This is a composite of images obtained with three instruments, operating at very different wavelengths. The 870-micron submillimetre data, from LABOCA on APEX, are shown in orange. X-ray data from the Chandra X-ray Observatory are shown in blue. Visible light data from the Wide Field Imager (WFI) on the MPG/ESO 2.2 m telescope located at La Silla, Chile, show the background stars and the galaxy’s characteristic dust lane in close to “true colour”.

    ESO/APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft)

    NASA/Chandra Telescope

    ESO WFI LaSilla 2.2-m MPG/ESO telescope at La Silla, 600 km north of Santiago de Chile at an altitude of 2400 metres


    MPG/ESO 2.2 meter telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres

    It’s surrounded by 31 dwarf satellites, plus another 15 candidates awaiting confirmation.

    The lead author of our Science paper — Oliver Müller from the University of Basel — has previously studied the Cen A system and found that the dwarf satellites are aligned along a plane. However, this specific planar geometry of Cen A occurs about 20% of the time in cosmological simulations (one out of five), so it didn’t seem too odd at first glance. But the picture changed drastically when we looked at the motions of the satellite galaxies.

    Q: What did you find?

    A: It turns out that the velocities of the satellite galaxies aren’t random, as we expected from cosmological simulations. After subtracting the so-called “recession velocity” due to the expansion of the Universe, the satellite galaxies to the south of Cen A are moving away from us, while the ones to the north of Cen A are approaching us. This is consistent with coherent rotation within the plane, similar to how the satellite dwarfs are moving around the Milky Way and the Andromeda Galaxy.

    Milky Way Galaxy Credits: NASA/JPL-Caltech/R. Hurt

    Andromeda Galaxy Adam Evans

    When we consider both the distribution and the motions of the satellite dwarfs, a configuration like Cen A becomes extremely rare in cosmological simulations: it has a probability of only 0.1%. In other words, we didn’t actually pick up a “weird” system out of thousands of “normal” ones — this can’t just be a coincidence. Instead, it seems likely that Cen A, Andromeda, and the Milky Way are normal galaxies after all, and that satellite planes are the rule rather than the exception. Perhaps there are many more planes of satellite galaxies out there just waiting to be discovered.


    Dwarf galaxies are arranged on a disc-shaped plane around the galaxy Centaurus A. Using the Doppler effect (a shift in spectral lines), their direction of motion and speed can be calculated. Credit: University of Basel/Oliver Müller

    Q: What are the major implications of this discovery?

    A: Essentially, our observations challenge the simulations. Planes of satellite dwarfs have been observed in all three major galaxies in the nearby Universe: the Milky Way, the Andromeda Galaxy, and now Cen A. This pattern is telling us something: since state-of-the-art cosmological simulations can’t explain how these planar structures are formed, perhaps we should start looking at alternatives.

    For example, there is an old idea from the Swiss astrophysicist Fritz Zwicky: dwarf galaxies may form during the encounter of two large galaxies, out of small debris that is ejected by tidal forces during the interaction. This idea was proposed again by the British astrophysicist Donald Lynden-Bell in the 1970s; he was one of the first to note the planar distribution of dwarf galaxies around the Milky Way and to point out that galaxy encounters may naturally explain such geometries and coherent motions. Dwarf galaxies formed in this way, however, should be free of dark matter, so people lost interest in such an idea as the predominant dark matter paradigm took over. Our results indicate that such “old” ideas deserve a closer look.

    4
    Here we see the result of the merger between two spiral galaxies, forming a central elliptical-like object called NGC 7252 with two large tidal tails. Tidal dwarf galaxies are currently forming within these tails. The optical image is overlaid with the gas distribution (blue) and ultraviolet emission (violet), probing the recent formation of new stars and highlighting the location of tidal dwarfs. Credit: Lelli et al. 2015, A&A

    Q: Did you face any challenges in your research?

    A: The observational aspect of this work was relatively easy because we used existing data. The velocities of the dwarf satellites were measured before by other authors using various facilities and techniques. We “only” had to collect and analyse them. The challenging part was to compare reality with simulations, taking into account possible observational biases and uncertainties. In particular, we considered two large public simulations. One — called Millennium II — uses only dark matter particles and neglects the possible effect of “baryonic processes”, like the formation of stars, supernova explosions, and so on. The other — called Illustris — tries to model these complex baryonic processes to form actual galaxies inside dark matter halos. However, both simulations give essentially the same result as far as the distribution and kinematics of dwarf satellites are concerned.

    Q: What do you personally find most exciting about this research topic?

    A: The current cosmological model is quite successful in explaining the Universe on large scales. However, it needs to postulate two unknown substances: dark matter and dark energy. Challenging the cosmological model on small scales is one way to move forward with our understanding of dark matter and fundamental physics.

    Q: So what’s your next step?

    A: Next, we will measure distances and velocities of more candidate dwarf galaxies around Cen A. This will improve our statistics and allow for a more accurate comparison with cosmological simulations. We will also look for similar planar structures around other large galaxies in the Universe.

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

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    Visit ESO in Social Media-

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

     
  • richardmitnick 9:43 pm on January 26, 2018 Permalink | Reply
    Tags: , , , , , ESOblog,   

    From ESOblog: “Protecting the Earth from Cosmic Clashes” 

    ESO 50 Large

    ESOblog

    1
    Science in Society

    65 million years ago, the most famous asteroid in history slammed into Earth and most likely exterminated the dinosaurs. Disconcertingly, we are no less likely to be to hit by an asteroid today than our ancient reptilian counterparts were — but luckily we have helpful tools at our disposal. In 2015 ESO joined the International Asteroid Warning Network (IAWN). To find out what this entails, we talked to Andy Williams, ESO’s Institutional Relations Officer, and Olivier Hainaut, an ESO astronomer in charge of NEO follow-up at the VLT.

    Q: What are asteroids and why should we be worried about them?

    Oli: An asteroid is “just” a rock, or a pile of rocks, that orbits the Sun. Some asteroids are dead comets — those that have lost their ices so the comet is covered by a rocky crust. My work at ESO focuses on minor bodies such as asteroids, comets and trans-Neptunian objects — including those with the potential to smash into Earth. We call these Near-Earth Objects, or NEOs. Currently, we know of about 17 000 asteroids and 100 comets that are classified as NEOs.

    2
    Meteor Crater on the Colorado Plateau in Arizona. This crater is 1.2 kilometres in diameter and was created by a 46-metre asteroid 50 000 years ago.
    Credit: NASA Earth Observatory

    A key number to remember with NEOs is 10: if an asteroid 10 metres across hit Earth, it would release about the same amount of energy as the Hiroshima bomb. As its effect would be localised to within a few square kilometres around the impact site, it’s unlikely to do a large amount of damage. Remember that the surface area of the Earth is huge and a lot of it is taken up by the ocean, so it would be incredibly unlikely — and extremely unlucky — for an asteroid 10 metres across to severely damage a populated area. But the energy that an object releases is proportional to the cube of its size — so in comparison, a 100-metre asteroid (with the same composition and speed as the 10-metre asteroid) would release 1000 Hiroshimas. An asteroid with a diameter of one kilometre would do much greater damage, and an asteroid of 10 kilometres would be like the one that killed off the dinosaurs. It would sterilise an entire continent and cause major global damage.

    On average, one of these huge 10-km asteroids strikes Earth every 50 million years, and the last one was 65 million years ago — meaning we are now overdue. Of course, I should mention that I’m not too worried about an asteroid wiping out all of humanity. We know about most asteroids of this size in the Solar System – we’ve studied their orbits, their characteristics, and we can predict their chance of impact. But as the asteroids get smaller, the less we know of them. We estimate that about 70–80% of asteroids from 500 metres to 1 kilometre in diameter are known, but only about 10% of asteroids 100 metres in diameter are known. The International Asteroid Warning Network (IAWN) is working to improve these numbers.

    Q: So what is the IAWN?

    Andy: The International Asteroid Warning Network aims to detect, track, and physically characterise Near-Earth Objects to determine which are potentially dangerous to Earth. The network is made up of scientific institutions, observatories, and a variety of interested groups — all of which can make observations of asteroids and NEOs. Participation in the network is voluntary and partners are funded with their own resources. They also agree to a policy of free and open exchange of all data submitted to the network.

    3
    Credit: Dan Durda

    Q: How did the IAWN form?

    Andy: The network has its roots in the United Nations Committee on the Peaceful Uses of Outer Space (UN COPUOS), which was established in 1959 shortly after the launch of Sputnik. NEO detection happened for years by observatories around the world, including ESO, but in 2002 the UN committee decided there should be a single team to oversee the detection, risk analysis and communication of NEOs and their dangers. By 2008 two vital organisations had been set up: the International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG). The establishment of these groups marked a tangible and essential step in protecting Earth from potential asteroid impacts, and the IAWN, in particular, was crucial in collecting and sharing information about potential space hazards. Then in 2013, the Science and Technology subcommittee (STSC) gave IAWN the official role of NEO detection. By cosmic coincidence the Chelyabinsk meteorite struck the atmosphere above Russia on 15 February 2013 during the STSC meeting, giving immediate impetus to this work!

    3
    A photo from the first COPUOUS meeting. Credit: UN Photo

    Q: What is ESO’s role in the IAWN?

    Oli: To search for asteroids you need a survey-type instrument such as Pan-STARRS, which continuously scans the whole sky with the aim of detecting moving objects. ESO’s telescopes are very powerful, but have a narrow field of view and so are used to observe specific objects; in other words, they are not suitable for discovering NEOs. So we work as part of a team. Other huge surveys detect asteroids, some of which are considered potentially hazardous — and some of these are threatening enough get on ESO’s “to-do list”. Our role is to target the high-risk asteroids that no other observatory can observe. If an object is small or far away, only big telescopes like ESO’s Very Large Telescope get called on to hone in and measure it.

    In collaboration with ESA, we’ve run an ongoing project on the VLT since 2015. The project is awarded 24 hours of observing time per year, and while this time is modest, it’s enough to follow-up all the potentially dangerous NEOs that cannot be observed by smaller telescopes. 58 high risk or difficult NEOs have been observed by the VLT so far, 24 of which were removed from the risk list—the others are still on the list, despite the VLT observations.

    Andy: It’s really important to note that as an intergovernmental organisation, ESO has a great responsibility to the public who ultimately pay for what we do. The Director General decides on the 24 hours set aside per year for asteroid observations using the VLT.

    Q: How do we calculate the risk and the probability of an asteroid hitting Earth?

    Andy: Short answer: it’s complicated. The risk is a combination of the likelihood that an asteroid will strike, how soon it will strike, and the effects it would have on Earth. Astronomers use the Palermo Technical Impact Hazard Scale, which combines these values and also compares it to the ‘background’ level of risk. We have to consider many variables.

    Firstly, the orbit of the asteroid must be determined, along with the chance its path could intersect with Earth’s and when this would happen. Next, the size of the asteroid is vital, as it provides the main indicator of its danger — a large asteroid would slam into Earth’s surface intact, while a smaller one would burn up harmlessly in our atmosphere. The danger also depends on composition; some asteroids are basically huge chunks of iron ore, which can hold together as they pass through the atmosphere, while others are loosely-bound dust, ice and rocks, which burn up more easily. Then we must consider the angle of incidence — whether the asteroid travels straight down or at an angle, passing through much more of the atmosphere. In this case, the asteroid experiences more friction and is more likely to reduce in size (and danger) or be vaporised altogether. For most NEOs, these parameters are unknown, so we have to work with average, typical values.
    The Chelyabinsk asteroid that struck Russia in February 2013 passed through Earth’s atmosphere at a 20-degree angle and was quite small, approximately 20 metres across. It skimmed the atmosphere like a pebble over water and fortunately exploded before it reached the ground.

    5
    The Chelyabinsk meteoroid fell to Earth on February 15, streaking across the sky above the city of Chelyabinsk, Russia, at 9:20 am local time.
    Credit: Marat Ahmetvaleev

    Q: What happens if we find an asteroid at high risk of hitting Earth?

    Andy: Certain criteria have been set up that trigger an impact response. If the probability of impact is greater than 1% for objects over 10 metres, IAWN must alert the Space Mission Planning Advisory Group (SMPAG), of which ESO became an observer on 11 October 2017. SMPAG then have the harder job of coming up with an international action plan and deciding on the criteria for action. If the probability of impact within 20 years is greater than 10% for objects over 20 metres, SMPAG must alert authorities and the United Nations to begin terrestrial planning, which includes determining a “risk corridor” on the earth’s surface. If the probability of impact within 50 years is greater than 1% for an object of over 50 metres, SMPAG must begin mission planning. Much of the current work of SMPAG involves analysing the various mission options.

    Q: And what are those options?

    Oli: There are many possible hazard mitigation methods that are being considered, all of which sound very dramatic and sci-fi. It might seem like the best option to avoid a large predicted impact is to destroy the asteroid — but this isn’t such a good idea. We don’t want to break up the asteroid because it would dramatically increase the number of impacts and the likelihood they’d hit human populations! Not to mention the difficulty of tracking all the fragments.

    6
    A close-up image of asteroid (25143) Itokawa taken by the Japanese spacecraft Hayabusa during its close approach in 2005.
    Credit: JAXA

    A much better option is to deflect the asteroid. One idea is to spray paint one side of the asteroid white, making it more reflective — so when photons from the Sun bounce off, their momentum will transfer to the asteroid, pushing it off course just enough to miss Earth. This technique is based on the phenomenon of the Yarkovsky effect. Another idea is to send up a small rocket to push the object gently off course over a long period — say, 10 years. Basically, if we know about a potential impact long enough in advance, we can do something about it. We already have the technology today.

    Andy: Like Oli said, the extent of our preparedness will largely depend on the amount of time we have — obviously a 20-year warning will be different to a 2-day warning! Lots of people are thinking about mitigating the hazard of asteroids — NASA has the Asteroid Impact and Deflection Assessment (AIDA) Mission, and ESA used to have Asteroid Impact Mission (AIM) although at present its funding is unclear.

    Q: Does the recent discovery of the interstellar asteroid `Oumuamua affect our understanding of NEOs?

    Oli: Our team at Pan-STARRS first spotted the `Oumuamua asteroid.

    Pann-STARS telescope, U Hawaii, Mauna Kea, Hawaii, USA, 4,207 m (13,802 ft) above sea level

    This was an interstellar object — the first ever discovered — that briefly became a Near-Earth Object, except it was travelling much faster, meaning it would have been extremely damaging if it struck the Earth.

    We think that over its lifetime, our Sun has ejected tens of trillions of objects into interstellar space, so it’s reasonable to assume that other stars, including our neighbours, have done the same. This means there are a huge number of interstellar objects travelling through space. But when you compare this with the sheer scale of the Universe, the likelihood of even coming across one is exceedingly slim — and the chances of an interstellar asteroid striking the Earth are negligible. Furthermore, there would be not much we could do to mitigate such an impact because we’d have just a few weeks’ notice. It is better to focus our efforts on the much higher risk from our own Solar System’s NEOs.

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

    Stem Education Coalition
    Visit ESO in Social Media-

    Facebook

    Twitter

    YouTube

    ESO Bloc Icon

    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

     
  • richardmitnick 8:44 am on January 26, 2018 Permalink | Reply
    Tags: , , , , ESOblog, , Protecting the Earth from Cosmic Clashes   

    From ESOblog: “Protecting the Earth from Cosmic Clashes” 

    ESO 50 Large

    ESOblog

    1
    Science in Society

    65 million years ago, the most famous asteroid in history slammed into Earth and most likely exterminated the dinosaurs. Disconcertingly, we are no less likely to be to hit by an asteroid today than our ancient reptilian counterparts were — but luckily we have helpful tools at our disposal. In 2015 ESO joined the International Asteroid Warning Network (IAWN). To find out what this entails, we talked to Andy Williams, ESO’s Institutional Relations Officer, and Olivier Hainaut, an ESO astronomer in charge of NEO follow-up at the VLT.

    Q: What are asteroids and why should we be worried about them?

    Oli: An asteroid is “just” a rock, or a pile of rocks, that orbits the Sun. Some asteroids are dead comets — those that have lost their ices so the comet is covered by a rocky crust. My work at ESO focuses on minor bodies such as asteroids, comets and trans-Neptunian objects — including those with the potential to smash into Earth. We call these Near-Earth Objects, or NEOs. Currently, we know of about 17 000 asteroids and 100 comets that are classified as NEOs.

    2
    Meteor Crater on the Colorado Plateau in Arizona. This crater is 1.2 kilometres in diameter and was created by a 46-metre asteroid 50 000 years ago.
    Credit: NASA Earth Observatory

    A key number to remember with NEOs is 10: if an asteroid 10 metres across hit Earth, it would release about the same amount of energy as the Hiroshima bomb. As its effect would be localised to within a few square kilometres around the impact site, it’s unlikely to do a large amount of damage. Remember that the surface area of the Earth is huge and a lot of it is taken up by the ocean, so it would be incredibly unlikely — and extremely unlucky — for an asteroid 10 metres across to severely damage a populated area. But the energy that an object releases is proportional to the cube of its size — so in comparison, a 100-metre asteroid (with the same composition and speed as the 10-metre asteroid) would release 1000 Hiroshimas. An asteroid with a diameter of one kilometre would do much greater damage, and an asteroid of 10 kilometres would be like the one that killed off the dinosaurs. It would sterilise an entire continent and cause major global damage.

    On average, one of these huge 10-km asteroids strikes Earth every 50 million years, and the last one was 65 million years ago — meaning we are now overdue. Of course, I should mention that I’m not too worried about an asteroid wiping out all of humanity. We know about most asteroids of this size in the Solar System – we’ve studied their orbits, their characteristics, and we can predict their chance of impact. But as the asteroids get smaller, the less we know of them. We estimate that about 70–80% of asteroids from 500 metres to 1 kilometre in diameter are known, but only about 10% of asteroids 100 metres in diameter are known. The International Asteroid Warning Network (IAWN) is working to improve these numbers.

    Q: So what is the IAWN?

    Andy: The International Asteroid Warning Network aims to detect, track, and physically characterise Near-Earth Objects to determine which are potentially dangerous to Earth. The network is made up of scientific institutions, observatories, and a variety of interested groups — all of which can make observations of asteroids and NEOs. Participation in the network is voluntary and partners are funded with their own resources. They also agree to a policy of free and open exchange of all data submitted to the network.

    3
    Credit: Dan Durda

    Q: How did the IAWN form?

    Andy: The network has its roots in the United Nations Committee on the Peaceful Uses of Outer Space (UN COPUOS), which was established in 1959 shortly after the launch of Sputnik. NEO detection happened for years by observatories around the world, including ESO, but in 2002 the UN committee decided there should be a single team to oversee the detection, risk analysis and communication of NEOs and their dangers. By 2008 two vital organisations had been set up: the International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG). The establishment of these groups marked a tangible and essential step in protecting Earth from potential asteroid impacts, and the IAWN, in particular, was crucial in collecting and sharing information about potential space hazards. Then in 2013, the Science and Technology subcommittee (STSC) gave IAWN the official role of NEO detection. By cosmic coincidence the Chelyabinsk meteorite struck the atmosphere above Russia on 15 February 2013 during the STSC meeting, giving immediate impetus to this work!

    3
    A photo from the first COPUOUS meeting. Credit: UN Photo

    Q: What is ESO’s role in the IAWN?

    Oli: To search for asteroids you need a survey-type instrument such as Pan-STARRS, which continuously scans the whole sky with the aim of detecting moving objects. ESO’s telescopes are very powerful, but have a narrow field of view and so are used to observe specific objects; in other words, they are not suitable for discovering NEOs. So we work as part of a team. Other huge surveys detect asteroids, some of which are considered potentially hazardous — and some of these are threatening enough get on ESO’s “to-do list”. Our role is to target the high-risk asteroids that no other observatory can observe. If an object is small or far away, only big telescopes like ESO’s Very Large Telescope get called on to hone in and measure it.

    In collaboration with ESA, we’ve run an ongoing project on the VLT since 2015. The project is awarded 24 hours of observing time per year, and while this time is modest, it’s enough to follow-up all the potentially dangerous NEOs that cannot be observed by smaller telescopes. 58 high risk or difficult NEOs have been observed by the VLT so far, 24 of which were removed from the risk list—the others are still on the list, despite the VLT observations.

    Andy: It’s really important to note that as an intergovernmental organisation, ESO has a great responsibility to the public who ultimately pay for what we do. The Director General decides on the 24 hours set aside per year for asteroid observations using the VLT.

    Q: How do we calculate the risk and the probability of an asteroid hitting Earth?

    Andy: Short answer: it’s complicated. The risk is a combination of the likelihood that an asteroid will strike, how soon it will strike, and the effects it would have on Earth. Astronomers use the Palermo Technical Impact Hazard Scale, which combines these values and also compares it to the ‘background’ level of risk. We have to consider many variables.

    Firstly, the orbit of the asteroid must be determined, along with the chance its path could intersect with Earth’s and when this would happen. Next, the size of the asteroid is vital, as it provides the main indicator of its danger — a large asteroid would slam into Earth’s surface intact, while a smaller one would burn up harmlessly in our atmosphere. The danger also depends on composition; some asteroids are basically huge chunks of iron ore, which can hold together as they pass through the atmosphere, while others are loosely-bound dust, ice and rocks, which burn up more easily. Then we must consider the angle of incidence — whether the asteroid travels straight down or at an angle, passing through much more of the atmosphere. In this case, the asteroid experiences more friction and is more likely to reduce in size (and danger) or be vaporised altogether. For most NEOs, these parameters are unknown, so we have to work with average, typical values.
    The Chelyabinsk asteroid that struck Russia in February 2013 passed through Earth’s atmosphere at a 20-degree angle and was quite small, approximately 20 metres across. It skimmed the atmosphere like a pebble over water and fortunately exploded before it reached the ground.

    5
    The Chelyabinsk meteoroid fell to Earth on February 15, streaking across the sky above the city of Chelyabinsk, Russia, at 9:20 am local time.
    Credit: Marat Ahmetvaleev

    Q: What happens if we find an asteroid at high risk of hitting Earth?

    Andy: Certain criteria have been set up that trigger an impact response. If the probability of impact is greater than 1% for objects over 10 metres, IAWN must alert the Space Mission Planning Advisory Group (SMPAG), of which ESO became an observer on 11 October 2017. SMPAG then have the harder job of coming up with an international action plan and deciding on the criteria for action. If the probability of impact within 20 years is greater than 10% for objects over 20 metres, SMPAG must alert authorities and the United Nations to begin terrestrial planning, which includes determining a “risk corridor” on the earth’s surface. If the probability of impact within 50 years is greater than 1% for an object of over 50 metres, SMPAG must begin mission planning. Much of the current work of SMPAG involves analysing the various mission options.

    Q: And what are those options?

    Oli: There are many possible hazard mitigation methods that are being considered, all of which sound very dramatic and sci-fi. It might seem like the best option to avoid a large predicted impact is to destroy the asteroid — but this isn’t such a good idea. We don’t want to break up the asteroid because it would dramatically increase the number of impacts and the likelihood they’d hit human populations! Not to mention the difficulty of tracking all the fragments.

    6
    A close-up image of asteroid (25143) Itokawa taken by the Japanese spacecraft Hayabusa during its close approach in 2005.
    Credit: JAXA

    A much better option is to deflect the asteroid. One idea is to spray paint one side of the asteroid white, making it more reflective — so when photons from the Sun bounce off, their momentum will transfer to the asteroid, pushing it off course just enough to miss Earth. This technique is based on the phenomenon of the Yarkovsky effect. Another idea is to send up a small rocket to push the object gently off course over a long period — say, 10 years. Basically, if we know about a potential impact long enough in advance, we can do something about it. We already have the technology today.

    Andy: Like Oli said, the extent of our preparedness will largely depend on the amount of time we have — obviously a 20-year warning will be different to a 2-day warning! Lots of people are thinking about mitigating the hazard of asteroids — NASA has the Asteroid Impact and Deflection Assessment (AIDA) Mission, and ESA used to have Asteroid Impact Mission (AIM) although at present its funding is unclear.

    Q: Does the recent discovery of the interstellar asteroid `Oumuamua affect our understanding of NEOs?

    Oli: Our team at Pan-STARRS first spotted the `Oumuamua asteroid.

    Pann-STARS telescope, U Hawaii, Mauna Kea, Hawaii, USA, 4,207 m (13,802 ft) above sea level

    7
    This artist’s impression shows the first interstellar asteroid: `Oumuamua. This unique object was followed closely by telescopes around the world including the VLT, which characterised its shape and colour. Credit: ESO/M. Kornmesser

    This was an interstellar object — the first ever discovered — that briefly became a Near-Earth Object, except it was travelling much faster, meaning it would have been extremely damaging if it struck the Earth.

    We think that over its lifetime, our Sun has ejected tens of trillions of objects into interstellar space, so it’s reasonable to assume that other stars, including our neighbours, have done the same. This means there are a huge number of interstellar objects travelling through space. But when you compare this with the sheer scale of the Universe, the likelihood of even coming across one is exceedingly slim — and the chances of an interstellar asteroid striking the Earth are negligible. Furthermore, there would be not much we could do to mitigate such an impact because we’d have just a few weeks’ notice. It is better to focus our efforts on the much higher risk from our own Solar System’s NEOs.

    Andy: The recent discovery of `Oumuamua was also very interesting because it was extremely well-publicised. Events like this are definitely useful for alerting the public to this issue, which is really necessary, as this is one natural disaster we could avoid by doing something about in advance.

    Q: How well do you think the public understands the risk of asteroids and NEOs?

    Andy: That’s a tough question! Obviously, films have had a huge role in creating a cultural awareness about these scenarios. I remember “Deep Impact” and “Armageddon”, both from 1998. I wonder what happened around that time to warrant two films in the same year about asteroids!

    Oli: It’s unfortunate to note that almost all the science and technical aspects in these two movies were wrong.

    Andy: Yes — these kinds of movies can, of course, be quite silly and over the top. The assessment of risk and probability is complex, and not necessarily easy to quickly explain, especially in a movie.

    But movies aren’t the only way the public can be made aware of asteroids. Asteroid Day aims to raise global awareness about asteroids. It’s held on the anniversary of Earth’s most harmful known asteroid-related event in recent history, the Tunguska event in Siberia on 30 June 1908. ESO recently became a partner of Asteroid Day, which is also officially recognised by the UN.

    8
    Artist’s impression of the planetary system around HD 69830 II, which likely includes an asteroid belt. Credit: ESO.

    Of course, there are many ways of communicating asteroids to the public. The absolute key is to raise awareness without alarming anyone. It’s vital to highlight that the known risk from NEOs is really incredibly low, and also that it’s one of the few natural disasters about which we would have plenty of advance warning. Unlike an earthquake, hurricane or volcano, we also have the technology to attempt to stop an impact from happening!

    Q: What does the future hold for asteroid detection and hazard mitigation?

    Andy: The next meeting of the International Asteroid Warning Network will be on the 30 January 2018, in Vienna. On the agenda is a review of the guidelines for public communication of the threat—the Torino Scale, which is like the Richter earthquake scale but for asteroid impacts.

    Oli: The next generation of survey telescopes is currently being built. In particular, the Large Synoptic Survey Telescope, an 8.4-metre telescope under construction in Chile, is expected to start observing in 2023. It will scan the sky for dangerous asteroids with a sensitivity about 100 times higher than current surveys, and it should discover up to 90% of the potentially hazardous asteroids larger than 150 metres within 15 years of operation.

    See the full article here .

    Please help promote STEM in your local schools.
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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

     
  • richardmitnick 1:51 pm on January 19, 2018 Permalink | Reply
    Tags: , , , , Dr Julien Milli - Paranal’s Adaptive Optics Scientist, ESOblog   

    From ESOblog: “Working atop Paranal – Dr Julien Milli, Paranal’s Adaptive Optics Scientist” 

    ESO 50 Large

    ESOblog

    19 January 2018

    1

    ESO’s Adaptive Optics Scientist at Paranal talks about life in the desert.

    Even in the pristine conditions of ESO’s Paranal Observatory in the high, dry Chilean desert, turbulence in the Earth’s atmosphere can distort starlight and blur astronomical observations. Astronomers are able to peer past this distortion using advanced technology that has become more and more refined in recent years. We’ve asked Dr Julien Milli, Paranal’s Adaptive Optics Scientist, to tell us about how his work provides ESO telescopes with a truly spectacular view of the Universe.

    Q: As Adaptive Optics Scientist at Paranal, you’re responsible for a crucial feature of some of the world’s most advanced telescopes. How does your work help keep ESO’s observations at the forefront of ground-based astronomy?

    A: Adaptive optics (AO) has indeed become a crucial component of Paranal’s instrumentation, and it will continue to have an even larger impact in the future — especially when ESO’s Extremely Large Telescope (ELT) begins operations. My work ensures that the astronomers and operators have the knowledge to work with these complex systems, and that these systems are combined with compatible atmospheric conditions so they give us the best possible performance.

    Q: How would you explain adaptive optics to a non-expert? Are there any analogous processes in day-to-day life?

    A: Have you ever tried to look at a coin sitting on the bottom of the swimming pool? It’s not as easy as it sounds — if the water is turbulent with waves or eddies on the surface, then the image of the coin will be distorted. If you snapped a long-exposure photo of the coin with a camera, it would be blurry. A similar thing happens in astronomy. The atmosphere actually behaves like water, or any fluid medium, and astronomers are trying to observe distant objects through this medium to see as many fine details as possible. But if the atmosphere is turbulent, then the image that a ground-based telescope creates of a star or a galaxy will be blurry.

    The first solution to this problem is to select astronomical sites with the least turbulence, such as in dry, high-altitude regions. The second, more high-tech solution is to correct the remaining turbulence by using a deformable mirror, which essentially changes its shape to adjust the light that reaches the telescope and compensates for the image distortion.

    2
    Inside the UT4 of the Very Large Telescope, the four laser guide stars point to the skies during the first observations using the MUSE instrument.
    Credit: Roland Bacon/ESO

    Q: So how did you become Paranal’s Adaptive Optics Scientist?

    A: I previously worked at ESO as a postdoctoral fellow, with duties on an extreme AO instrument called SPHERE. SPHERE is a system built to detect exoplanets by direct imaging. Because planets detectable from Earth orbit close to bright stars, we needed to use adaptive optics to get very sharp images to try to detect exoplanets despite the glare of their parent stars. I gained a lot of experience by operating this complex system. In the past, I also used the NACO instrument for my scientific research, which is also equipped with AO, so I was already acquainted with the two larger AO systems in operation at Paranal at that time. This really helped me to become Paranal’s Adaptive Optics Scientist.

    Q: Paranal must be one of the most remarkable places in the world to work — what’s a working day like in the midst of the Atacama Desert?

    A: There is no typical working day, which is part of the charm of Paranal. Your activities can vary widely depending on whether you work during the day (for instance, as a day astronomer or shift coordinator), or during the night. In the day, you check the data obtained the previous night, make sure the corresponding calibrations are made, and prepare the instruments for the coming night. You also interact a lot with engineers, who use the day to perform necessary maintenance on the telescopes. When I work at night, on the other hand, I usually wake up in the afternoon and enjoy a swim in the pool or a run in the desert before getting ready for a night of observations. If we have visiting astronomers, we bring them into the control room and discuss their observation strategy. Otherwise, we interact mostly with the telescope and instrument operators — they are in charge of the telescope side of the observations, and are also experts in using the instruments. So there’s a lot of variety!

    3
    This amazing panorama shows the observing platform of ESO’s Very Large Telescope (VLT) on Cerro Paranal, in Chile.
    Credit: ESO/H.H. Heyer

    Q: What’s it like to live in such an extreme region?

    A: Paranal is a very special place, and the contrast between the desert and the inside makes the experience of living there unforgettable. Outside, the desert is majestic, overwhelmingly silent, with endless hills on the horizon, an intense blue sky in the day and a stunning star-studded sky at night, inviting you to think about how tiny humans are in the Universe. This is in huge contrast with the inside of the observatory, where engineers, operators, astronomers are actively working in this hive to deliver the best-quality data from the telescopes and their instruments. The desert can also be dangerous, with very dry air and high solar radiation — again in contrast with the well-organised logistics inside the observatory, making sure everyone working there feels comfortable.

    Q: You’re originally from France — is there anything you miss about home? Conversely, when you’re in France do you miss anything about Chile?

    A: Like most French people living in Chile, I miss the cheese and any French cheese specialities like raclette, fondue, and tartiflette! When I’m in France I miss “palta”, the Chilean word for avocado, which is a very common ingredient used in every kind of meal in Chile.

    Q: What’s it like to work for ESO?

    A: Through working at ESO, I’ve greatly improved my technical expertise in the wide range of instruments operating at Paranal. This has directly impacted my scientific research; it means I can write successful proposals for my own observations because I really understand the ideal conditions for each instrument I want to use.

    Working at Paranal, or more generally in an observatory, is a good opportunity to understand the complete data cycle, and I really enjoy following studies from the original idea for an observation right up until the publication of the results. At ESO I’m also lucky enough to interact with a wide range of people, from engineers to operators to visitors — so many more different kinds of professionals than if I had a job in a research institute. This means I can get to know many fascinating fields of astronomy that aren’t my own area of expertise.

    ESO bird’s eye view of the Paranal platform, elevation of 2,635 metres (8,645 ft) above sea level


    A birds-eye view of ESO’s Very Large Telescope (VLT) at the Paranal Observatory, located in the remote, sparsely populated Atacama Desert in northern Chile. Credit: J.L. Dauvergne & G. Hüdepohl (atacamaphoto.com)/ESO

    Q: Do you still have time for your own research? If so, what are you working on?

    A: Keeping our own research up-to-date is actually part of working at ESO, so I spend about a third of my time on my own scientific research. I try to understand how planetary systems form and evolve, by looking at a particular component of most planetary systems: Kuiper belt analogues, which are also known as debris discs. I recently tried to understand why so few debris discs were detected through their scattered light — I led a survey of 55 stars believed to host such a disc, but without detection of scattered light so far. We ended up discovering several new discs, plus a low-mass companion, most likely a brown dwarf.

    Q: Tell us a bit about the algorithms you have developed to process high-contrast data.

    A: When we try to detect material around a star — for example, a disc or a planet — this material is almost always extremely faint compared to the star, which is typically a hundred thousand times brighter. For instance, one of the first exoplanets, Beta Pictoris b, was detected in 2008 but its signal was already present in images as old as 2003. The faint signal had been missed in the first place because data processing techniques at the time weren’t efficient enough to reveal it among the glare of its host star. So in order to see what’s around the star, we need to somehow remove the star’s bright halo. I develop algorithms to do this. It’s an exciting new area with a lot of room for improvement, and it allows me to express my scientific creativity by testing new ideas. It’s an area where my technical knowledge of the instruments, cameras, observation strategies, and atmospheric conditions is a real asset, allowing me to fine-tune data processing techniques.

    5
    This artist’s rendering of the Extremely Large Telescope (ELT) shows how the telescope’s laser guide star system (a fundamental element of any AO system) will look in action in 2024. Credit: ESO/L. Calçada

    Q: The upcoming ELT will be a revolutionary telescope and will come equipped with adaptive optics. How will experience from the VLT improve adaptive optics in the future?

    A: Today, the fourth Unit Telescope of the VLT (UT4) is already a fully adaptive telescope, with a large secondary adaptive mirror. The technical experience gained by operating such a large adaptive mirror will be extremely valuable for the ELT, which will face additional challenges, especially because its primary mirror will be made up of hundreds of segments working together as a whole. Optimising the schedule and the time allocation of the science programmes on the ELT will also benefit from our experience with the AO instruments on the VLT. AO systems require very specific atmospheric conditions to work, so we’ll need time turbulence predictions and real-time schedule optimisation tools in order to avoid wasting precious ELT observation time.

    See the full article here .

    Please help promote STEM in your local schools.
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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

     
  • richardmitnick 3:41 pm on January 12, 2018 Permalink | Reply
    Tags: , , , Beta Pictoris star system, , , ESOblog, PicSat, PicSat is is one of the few CubeSats worldwide with an astrophysical science goal,   

    From ESOblog: “Combining the freedom of a CubeSat with the power of an ESO telescope” 

    ESO 50 Large

    ESOblog

    How ESO’s HARPS will help PicSat the CubeSat to unravel the mysteries of the Beta Pictoris star system.

    12 January 2018

    A shoebox-sized satellite called PicSat, developed in record time by a small team of scientists and engineers at the Paris Observatory in France, has just been launched into space to study the Beta Pictoris star system. PicSat will be assisted in its mission by the HARPS instrument on the ESO 3.6-metre telescope, which will make follow-up observations to PicSat’s detections. This will be the first time that a small modular satellite — a CubeSat — and a ground-based telescope work together to address some of the mysteries of the Universe. We speak to Sylvestre Lacour, an astrophysicist and instrumentalist who leads the PicSat team, to find out more about this exciting project.

    1
    Science@ESO

    Q. First of all, tell us a bit about why you chose to look at the Beta Pictoris star system.

    A. Having celebrated only roughly 23 million years of life, Beta Pictoris is a very young star, astronomically speaking. At about twice the mass and size of the Sun, and just 63.4 light years away, it is relatively easy to observe. Over the past decades, Beta Pictoris has been a popular target for astronomers studying the early stages of star and planet formation, with those astronomers often using ESO facilities. In 2008 a team of French astronomers discovered a giant gas planet orbiting Beta Pictoris. The planet, baptised Beta Pictoris b, has about seven times the mass of Jupiter and orbits its host star at around ten Astronomical Units (AU). The distance between Beta Pictoris and Beta Pictoris b is similar to that between the Sun and our neighbouring ringed planet, Saturn.

    2
    Satellite and ground-based telescopic observations of Beta Pictoris revealed the presence of an outer, dusty, debris disk and an inner clear zone about the size of our Solar System. In 2008, infrared observations from ESO telescopes provided evidence for a giant planet.
    Credit: ESO/A.-M. Lagrange et al.

    A few years ago it became clear that from the viewpoint of the Earth, either Beta Pictoris b, or at least its Hill Sphere, will transit in front of Beta Pictoris. The Hill Sphere of a planet is its gravitational sphere of influence — the region around it that dominates the attraction of rings and moons. Observing a planetary transit would tell us more about the young planet, for example about its size and the chemical composition of its atmosphere. Observing a Hill Sphere transit could tell us about the properties of objects around Beta Pictoris b, for example, its moons or rings.

    Q. Sounds exciting! So what exactly happens during a transit?

    A. During a transit, the planet blocks the light from a small part of the star, diminishing the amount of starlight that reaches us. A telescope captures the light from the star, and a sensitive instrument called a photometer accurately measures the amount of light received. The main goal of PicSat will be exactly that — to monitor the brightness of Beta Pictoris continuously, so as to capture the little revealing dip in its lightcurve as the planet Beta Pictoris b, or its Hill Sphere, passes in front of it.

    A transit of Beta Pictoris b itself would take a few hours and would show a clear dip in the light curve. Because the reach of the Hill Sphere extends a very long way from the planet, a transit of only the Hill Sphere could take up to several months and could result in a more irregular light curve as several rings or moons pass by.

    4
    A diagram showing the dip in brightness of a host star as it is transited by a planet. By measuring the amount of dip in brightness and knowing the size of the star, scientists can determine the size of the planet. Credit: NASA Ames

    Q. And why did you choose to build PicSat for this job? Couldn’t an existing ground-based telescope do exactly the same thing?

    A. So far it has only been possible to estimate an approximate time for the moment of transit — we believe that it should occur by summer 2018. Because of this uncertainty, we needed something that could continuously monitor the star system. Ground-based telescopes can only observe at night and are in high-demand — they are too busy to make continuous observations. So we decided that sending a satellite into space would be the only way to ensure that we capture this phenomenon. PicSat will orbit around the Earth from pole to pole, as the Earth rotates below it. This means that PicSat can always see to either side of the Earth without its view being blocked, allowing it to continuously observe Beta Pictoris.

    5
    With a polar orbit, PicSat will pass over the poles of the Earth, constantly keeping an eagle eye on Beta Pictoris.
    Credit: NASA illustration by Robert Simmon

    6
    The fully assembled PicSat, which consists of three cubic units stacked on top of each other.
    Credit: PicSat CubeSat

    When PicSat observes photometrically that a transit is taking place, we will use an online form to alert people working at the ESO 3.6-m telescope. As soon as possible after they have been alerted, they will use the HARPS (High Accuracy Radial velocity Planet Searcher) instrument to make detailed spectroscopic observations. The photometric (measurement of the amount of light) and spectroscopic (measurement of the wavelength distribution of light) observations can then be combined to find out much more about the star system.

    Q. We’d love to hear a bit more about PicSat itself.

    A. PicSat, a contraction of Beta Pictoris and Satellite, is composed of three standard cubic units with side lengths of 10 cm. The project started in 2014 when I proposed using CubeSat technology to observe the predicted transit. I gathered a small local team and together we worked hard to design and build PicSat. It is incredible that in less than four years we have reached a stage where PicSat is being launched!

    One really cool thing about PicSat is that it is one of the few CubeSats worldwide with an astrophysical science goal, and is the first CubeSat aiming to provide answers in the challenging field of exoplanetary science.

    Q. You say that PicSat is made of three cubic units — do these units each have different roles in the operation of the satellite?

    A. Absolutely! The top and middle cubic units house the “science payloads”, whilst the bottom unit contains the onboard computer.

    More specifically, the top cubic unit of PicSat contains a small telescope. Thanks to the brightness of Beta Pictoris, the mirror of this telescope can have a diameter of just 5 cm.

    This telescope sends the light from Beta Pictoris down into the middle unit. Here, a tiny optical fibre, three micrometres in diameter (or about a fifth of the size of a thin human hair) collects the light and guides it onto a sensitive photodiode that accurately measures the arrival time of each individual photon. Because light will be guided by the tube-shaped fibre, unwanted light will be prevented from entering the photodiode. This allows for a very accurate measurement of the star’s brightness. Imagine looking through a tube — you are able to focus much more easily on a distant object than if you use just your unaided eye because the tube prevents peripheral light from entering your eye. Optical fibres are often used in ground-based telescopes, but this will be the first time an optical fibre is flown in space for astronomical observations.

    However, PicSat will wiggle and wobble a little as it orbits the Earth, so the accuracy with which it points at Beta Pictoris wouldn’t be good enough for the telescope to send all the light from the star into the small fibre all the time. We devised an innovative solution to this problem by connecting the optical fibre to a small plate, a “piezoelectric actuator”, that can track the star and immediately follow it to remain on target.

    7
    A “naked” PicSat, with its cover removed so that its science payload is visible. The optical fibre is in the centre of the image.
    Credit: NASA illustration by Robert Simmon

    The bottom unit of PicSat contains the onboard computer for operating the satellite, communicating with Earth, raw pointing of the telescope and other important monitoring tasks. The whole satellite is clothed in solar panels that provide the satellite with energy, but it does not need a lot. In fact, the total power consumption of PicSat is about 5 watts, similar to a small light bulb!

    8
    PicSat’s compact optical system collects the light from Beta Pictoris and the electronics track the star’s position. Inbuilt electronics include a precision stage for moving the optical fibre and a state-of-the-art photodiode.
    Credit: PicSat CubeSat

    Q. And what exactly will happen when PicSat observes a transit?

    A. If PicSat detects the beginning of a transit, whether it be Beta Pictoris b, its Hill Sphere, or any other transit like phenomena, ESO’s 3.6-metre telescope will immediately be put into action. Dr Flavien Kiefer from the Institut d’Astrophysique de Paris will lead the ground-based observations and has guaranteed time using HARPS to support PicSat. He will be the one to respond quickly to our online alert.

    8
    The ESO 3.6-metre telescope at La Silla. This telescope is mounted with the High Accuracy Radial velocity Planet Searcher (HARPS), an instrument dedicated to the discovery of exoplanets. Credit: Y. Beletsky (LCO)/ESO

    Another exciting thing this project might address is that the Beta Pictoris system is rich in objects thought to be comet-like, which have often been observed spectroscopically by ESO telescopes. The presence of these objects has been inferred through the absorption lines of elements such as calcium, sodium and iron present in the object’s tails, which appear in the spectra and disappear again as they transit the star. However, a photometric detection of the dust in a cometary tail passing in front of Beta Pictoris has not yet been achieved. PicSat could well provide us with the first of these observations, which would confirm that these objects are indeed exocomets. If combined with an immediate follow up by HARPS, this would provide new and unique information about such comets and the system as a whole.


    Astrophysicist and PicSat team member Flavien Kiefer (Institut d’Astrophysique de Paris, France) talks about the detection of exocomets in the Beta Pictoris system. Credit: PicSat CubeSat

    Q. And finally, I’m curious to know what could go wrong and how you would deal with any problems that might arise.

    A. As with any space mission, things can, of course, go wrong! This is the first time that our team (and in fact the LESIA lab!) has constructed an entire satellite, and with a small team, low budget and short time-scale, risks are higher than for conventional missions.

    We were most concerned about the launch, but that was a huge success this morning!! So the next stage is to cross our fingers that the automatic initiation sequence that will start PicSat works successfully. At the end of this sequence, antennas will deploy — critical for communication with the satellite. Antenna deployment and pointing at Beta Pictoris have been tested many times in the lab, so we are hopeful that they work in space as well.

    As for how we would deal with it, well that really depends on the problem! Fortunately, we have a varied and intuitive team and we believe can adapt to most situations.

    The PicSat satellite was successfully launched at 05:00 CET on Friday 12 January 2018. Follow the progress of the mission and find out more about the project at https://picsat.obspm.fr.

    Links

    PicSat website
    PicSat YouTube channel
    PicSat Flickr account
    PicSat Beta Pictoris Star System Info Sheet
    PicSat Twitter account

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

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    Visit ESO in Social Media-

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

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    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

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    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

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    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

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    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

     
  • richardmitnick 1:41 pm on December 25, 2017 Permalink | Reply
    Tags: , , , , , ESOblog, Stefano Covino is an astronomer with the Istituto Nazionale di Astrofisica (INAF), Stephen Smartt is Director of the Astrophysics Research Centre at Queen’s University Belfast, The makings of the ground-breaking gravitational waves discovery,   

    From ESOblog: “The makings of the ground-breaking gravitational waves discovery” 20 October 2017 It is worth your time 

    ESO 50 Large

    ESOblog

    20 October 2017 [Missed this one first time around, just caught up with it. It is worth your time.]

    1

    Have you heard the game-changing news? For the first time ever, astronomers have observed the visible counterpart of a gravitational wave source. Gravitational waves were detected passing by Earth on 17 August, and telescopes around the world leapt into action to locate their source — spearheaded by ESO’s fleet of telescopes in Chile. Together, this global collaborative effort observed both gravitational waves and light from the same event, indicating that the source was the merger of two neutron stars. The drop-of-a-hat observing campaign involved dozens of scientists across the globe, and we asked two of them what it was really like to experience such a historic discovery first-hand. Here, we talk to Stephen Smartt (Queen’s University Belfast, UK) and Stefano Covino (INAF–Osservatorio Astronomico di Brera, Italy).

    Q: It all began on 17 August 2017. Tell us about the moment you received that fateful notification. Where were you? What were you doing?

    Stefano Covino (SC): The middle of August is the holiday period in Italy, so on 17 August I was relaxing at my place with my young daughters: Sofia (5) and Aurora (almost 3). My wife Maddalena, a medical doctor, was busy at a nearby hospital. I was enjoying spending time with my girls when my smartphone began to ring obsessively. When I unlocked it I found a series of messages, some automatic, some with comments from my colleagues at the GRAWITA collaboration, in particular from Marica Branchesi, our LIGO–Virgo expert — a new gravitational wave event had been reported!



    1
    GW170817 Press Release
    LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars
    Discovery marks first cosmic event observed in both gravitational waves and light.

    Stephen Smartt (SS): I’d just sat down at my computer after a lunchtime run, feeling great, when the alert flashed up at 14:22. Suddenly I felt even better because LIGO and Virgo had just reported a gravitational wave signature — probably caused by neutron star binary merger, which we’d never seen before. When I learned that Fermi and INTEGRAL had reported a gamma ray detection within two seconds of the LIGO Hanford timing, it was truly a wow! moment — this is what we’d been waiting for.


    NASA/Fermi Telescope

    ESA/Integral

    Q: Why was this such an exciting moment?

    SC: Well we’d actually been alerted to another event just three days before, but the preliminary analysis of this new event indicated that it was the result of a neutron star merger. This was partly unexpected but intensely desired, because this kind of event is predicted to have a visible counterpart, so we can observe the aftermath with telescopes all over the world. In an instant, we had the chance to link gravitational waves and electromagnetic astronomy — something that had never been achieved before. Wow!

    SS: Like Stefano said, we’ve seen several of these kinds of alerts before. Sometimes they come at inconvenient times — like back in 2015, I was just about to turn in on Boxing Day when the highly-significant second black hole merger event was found by LIGO and it was an all-night scramble to marshal the Hawaiian Pan-STARRS and ATLAS telescopes for the coming darkness, postponing my holiday.


    Pann-STARS telescope, U Hawaii, Mauna Kea, Hawaii, USA, 4,207 m (13,802 ft) above sea level

    ATLAS telescope, First Asteroid Terrestrial-impact Last Alert system (ATLAS) fully operational 8/15/15 Haleakala , Hawaii, USA, Altitude 4,205 m (13,796 ft)

    But this time, it looked like the gravitational waves were produced by the merging of two neutron stars, which was predicted to be accompanied by a bright burst of electromagnetic radiation — and if we could find the source, it would actually be the first identification of a gravitational wave source. The race was on!


    This artist’s impression video shows how two tiny but very dense neutron stars merge and explode as a kilonova. Such a very rare event is expected to produce both gravitational waves and a short gamma-ray burst.These objects are the main source of very heavy chemical elements, such as gold and platinum in the Universe
    Credit: ESO/L. Calçada. Music: Johan B. Monell (www.johanmonell.com)

    Q: So the next step was to find the source — how did you know where to look in the sky?

    SC: That’s the tricky part. Just because we were incredibly excited didn’t mean the way forward was easy. Gravitational wave detectors are wonderful pieces of technology, but they’re currently only able to tell us the region of sky where the event was measured, not a specific location. This time, however, we got lucky. The Fermi and the INTEGRAL high-energy satellites detected a signal a couple of seconds after the gravitational wave event — an amazing feat by itself! And by combining the information, we managed to narrow the source down to a reasonably small area of the sky.

    SS: Actually, the very first map of the sky from LIGO–Virgo showing us the source’s direction was simply enormous. It covered a region of about half the whole sky, which didn’t narrow down our search at all! Maybe this is just chance coincidence, I thought. We’ve seen them before. But it turns out the huge area was just due to a noise glitch, and by midnight (GMT) on that same day, LIGO–Virgo had heroically reanalysed all the data and come up with a new, smaller region in the south, low in the sky at dusk.

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    This image shows areas of the Milky Way where previous cosmological events have been localised by LIGO, starting with gravitational waves detected in 2015 (GW150914, LVT151012, GW151226, GW170104). More recently with the addition of VIRGO the LIGO–Virgo network was able to more accurately localise gravitational-wave signals (GW170814, GW170817). The “yellow banana” is the only gravitational wave source in this image to have been produced by merging neutron stars, the others all being caused by merging black holes. Credit: LIGO/Virgo/NASA/Leo Singer/Axel Mellinger

    Q: But how did you narrow it down to find the source itself?

    SS: There are a couple of ways we could have done this. Firstly, we could have used a wide-field telescope to scan the region (which is about the size of 100 full Moons) and spot what new objects had appeared. Secondly — and this is the option that many telescopes went with — we could plausibly guess that the object is most likely located where most of the other stars are, and so many teams decided to take a focused look at the 10 or 100 biggest galaxies in the region. Handily, LIGO–Virgo also estimated how far away the event was (about 130 million light-years) which gave everyone a three-dimensional space to search in. Picking the biggest galaxies from that actually wasn’t too hard.

    Q: Who made the initial observations? Was there a call to action for astronomers around the world?

    SS: Pretty much! The position of the source, low in the sky, was not great for observatories in places like Hawaii but was well-placed for Chile. So all of a sudden, Chile became the best astronomical site in the world to search for the electromagnetic counterpart of the event. Of course, the big, wide-field telescopes DECam and VISTA were immediately scheduled, but even small telescopes (40-cm to 1-m) were enlisted to conduct interesting searches!

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet


    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    SC: With a few colleagues from the INAF–Brera Astronomical Observatory — Sergio Campana, Paolo D’Avanzo and Andrea Melandri — I planned a set of observations with the REM telescope, which is small, rapidly-pointing INAF telescope located at ESO’s La Silla Observatory.

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    The Rapid Eye Mount (REM) telescope is a 60 cm rapid-reaction automatic telescope at La Silla, and since October 2002 it has been operated by the REM team for the INAF (Italian National Institute for Astrophysics),

    We, along with many other colleagues around the world, targeted some of the brightest galaxies at a compatible distance in the sky area of interest. Still, it was a very difficult search because the area was observable only for a limited amount of time after sunset.

    Q: And what did you find that first night of observing?

    SS: Within the first hour of observing in the Chilean dusk, seven telescopes spotted the same source of light. It was first announced as the possible counterpart by Ryan Foley’s University of Santa Cruz team using the little Swope 1-m telescope, at Las Campana, a few tens of kilometres from La Silla.


    Carnegie Institution Swope telescope at Las Campanas, Chile, 100 kilometres (62 mi) northeast of the city of La Serena. near the north end of a 7 km (4.3 mi) long mountain ridge. Cerro Las Campanas, near the southern end and over 2,500 m (8,200 ft) high, at Las Campanas, Chile

    The new source was in the galaxy NGC 4993, an otherwise fairly normal and unremarkable galaxy at the same distance that was estimated by LIGO–Virgo. Six other teams also reported the same detection within those first few hours, having guessed that this galaxy had a good chance of hosting the object.

    SC: The REM telescope was scheduled to observe NGC 4993 20 minutes later, and indeed our observations also showed this bright, previously-uncatalogued source. The Swift satellite also observed it, quite bright in the ultraviolet part of the spectrum.

    NASA/SWIFT Telescope

    Is it the counterpart we’re looking for? I wondered. Is it actually related to the gravitational waves event? It was still difficult to say; finding new sources is not very unusual. Only direct observations could reveal the nature of this source. But the visibility period of the field was over. From Chile, we had to try again the next night.

    5
    This image from the VIMOS instrument on ESO’s Very Large Telescope at the Paranal Observatory in Chile shows the galaxy NGC 4993, about 130 million light-years from Earth. To the top-left of the galaxy is a tiny pinpoint of light, never seen before in this galaxy, which appeared suddenly and unexpectedly. It is, we now know, the light from the first ever observed kilonova, produced by two merging neutron stars Credit: ESO

    ESO VIMOS


    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    Q: Did other telescopes around the globe pick up where you left off?

    SS: They sure did. As night marched west across the globe, the source was visible but very low in the sky for the next observatories able to spot it — in Hawaii. Six hours later, Subaru and Pan-STARRS announced they had picked up the source.


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level


    Pann-STARS telescope, U Hawaii, Mauna Kea, Hawaii, USA, 4,207 m (13,802 ft) above sea level

    I’ve been involved in Pan-STARRS for a long time and it’s a great facility to do this type of search. When Ken Chambers (Pan-STARRS Director) heard the news about the detection, he decided to focus on getting colours for the object in the 15 minutes or so it was visible.

    We followed it dutifully over the next few nights all around the world. Ken and his expert observing team in Hawaii drove Pan-STARRS to its elevation limit, pointing “down in the dirt” at twilight to spot the source low on the horizon. With our reliable Pan-STARRS data analysis pipeline, we could carefully monitor whether the object changed its brightness. The staggered observations from Hawaii, then Australia and South Africa and back to Chile again, showed us the object was fading fast. We wondered whether it could still be a variable star from our own galaxy, getting in the way of our observations, or perhaps even a distant supernova. But if we ruled out those two possibilities, the object was a real contender for the source of the gravitational waves. It was in the same area of the sky, at the same distance as LIGO–Virgo estimated… Everyone was thinking the same thing — is this actually it?

    Q: So these observations continued over many days — what were they like?

    SC: The day after the discovery of the source, we decided to investigate its nature with the best resources we had. And so the intensive campaign began, stretching over 10 days following the initial report. It was frankly impressive. The days were filled with frenetic and exciting activity. My team was remotely watching different units of ESO’s Very Large Telescope pointing at the same targets and simultaneously securing polarimetry, spectroscopy and photometry. It was truly a fusion of technology and passion at their best. And day by day, the evidence became more convincing that we were witnessing an astrophysical object that had been previously theorised, but never observed before: the long-sought connection between gravitational waves and electromagnetic astrophysics.

    SS: Observations took place over the next 10 days all around the world. For my team, we very luckily had five nights of the extended PESSTO survey coming up on ESO’s New Technology Telescope in Chile.


    ESO/NTT at Cerro La Silla, Chile, at an altitude of 2400 metres

    A rapid telecon led to plans for the coming nights with our two observers Joe Lyman and David Homan. Janet Chen triggered the MPG/ESO 2.2-metre telescope to observe NGC 4993 every night.


    MPG/ESO 2.2 meter telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres

    We needed a spectrum — the first one came from Magellan, taken within the first night by Maria Drout, and was just blue and featureless.

    Carnegie 6.5 meter Magellan Baade and Clay Telescopes located at Carnegie’s Las Campanas Observatory, Chile. over 2,500 m (8,200 ft) high

    We often see transients like this, so it was certainly unusual but not conclusive. As night came round again 24 hours later, we got that first conclusive spectrum. I waited at home, in contact with Joe and David, and they sent through the spectrum as soon as the exposure finished. As the first spectrum plot popped up on my screen, at 02:14 am on 19 August, I was thinking this really could be decisive.

    It was most definitely not a supernova, not a variable star, and not anything I’ve ever looked at before. PESSTO has classified over 1000 astronomical transients and none of them look like this. I sent the description around to PESSTO and the global network of observers. There was no hydrogen, helium, oxygen, calcium, silicon, or carbon in the spectrum. Others started to get their spectra from the optical to infrared too; we triggered ESO’s Very Large Telescope, and the reports all lined up. My former student Matt Nichol, now at Harvard, saw the same thing as me from his spectrum at another Chilean telescope on the same night. At this point, about 36 hours after the gravitational wave discovery, everybody really thought this was it: the electromagnetic counterpart.

    Q: Tell us: why this is such an important and exciting result?

    SS: Honestly, it’s a triumph for a very talented group of theoretical astrophysicists. Over the last 20 years, they had predicted that neutron star mergers would produce electromagnetic signals just like what we were seeing: blue, turning red, fading fast. The light is powered by heavy radioactive elements that were created in the first few moments of the merger. The name “kilonova” was coined for this phenomenon in 2010 by Brian Metzger — because it’s 1000 times brighter than a nova. It’s quite amazing that these physical models predated the discovery by years, but ended up being very similar to the data that we actually saw!


    This animation is based on a series of spectra of the kilonova in NGC 4993 observed by the X-shooter instrument on ESO’s Very Large Telescope in Chile.
    They cover a period of 12 days after the initial explosion on 17 August 2017. The kilonova is very blue initially but then brightens in the red and fades
    Credit: ESO/E. Pian et al./S. Smartt & ePESSTO/L. Calçada

    ESO X-shooter on VLT at Cerro Paranal, Chile

    Q: After the team makes their observations, what’s next in the scientific process?

    SS: In short: you write papers and get them published! Knowing how groundbreaking this was — knowing that this was probably the optical counterpart of merging neutron stars and the first identification of a gravitational wave source — I realised we had to act fast to analyse our observations thoroughly and get our results out there. There’s a lot of intellectual horsepower in the PESSTO, Pan-STARRS, and ATLAS teams, and I knew if I could harness that talent rapidly, then we could quickly work out what was going on. The team was formed and off we went — and you can read the result in the press releases and in our Nature paper. Superb work by our theory team of Anders Jerkstrand, Michael Coughlin, Stuart Sim and Luke Shingles showed that this is indeed a kilonova, associated with merging neutron stars!

    SC: I began to work intensively on our team’s paper along with Klaas Wiersema (now at the University of Warwick in the UK), who is co-responsible for the polarisation programme. It’s always a special period when you finally have your data, notes and plots and then try to organise everything in a coherent way. It was also a period of intense, rapid-fire interaction with the journal editors, who made exceptional efforts to allow us to publish at the right time at the end of the embargo period.

    Q: It must have been an incredibly busy and challenging period.

    SC: It really was! I didn’t sleep a whole night for the first couple of weeks after the event, but we were so excited that we didn’t really feel tired.

    SS: As it happens, as all this science frenzy was going on, I was in the middle of a training program for the Dublin Marathon. I’d been fortunate to be chosen by Irish Olympic Athlete Paul Pollock to be part of his first coaching project, Dream Run Dublin. The peak training period ran from mid-August to early September, so the day after the spectrum came through, I ran 20 miles faster than I’ve ever run before. Running keeps my head clear. In the middle of writing and analysing and checking all data, sometimes you can hit a wall. I find that getting outside and going for a run can lift this mental block. Could I keep this going, writing the paper with a deadline six weeks away (I could see the late nights coming!) and also keep up with the coaching program, with the goal of breaking 3 hours for the marathon? “Of course you can — go for it,” my wife Sarah said. “Easy,” my coach said — and he was right. The training is now over and in two weeks, I’ll be waiting at the starting line of the Dublin Marathon. 2:59:59 will mean success; 3:00:01 will mean failure. Let’s wait and see. In any case, the kilonova paper is finished and published, and the marathon of a new era of astronomy is underway!

    Q: And finally: How did it really feel to be part of such an extraordinary and landmark event?

    SS: I’ll remember these eight weeks for a long time. I’m very fortunate to work with a great group of scientists and it has been a privilege and a pleasure to lead the team and be part of this truly historic event.

    SC: It was a privilege to be on the frontline of these epochal events. Of course, we all like to see our work recognised and feel that we’ve contributed to our field of research, but this time was different. You had the precise feeling that something historic was happening, and I’m proud to have been a small part of this big event. Most highly-talented scientists have never had this privilege. These past two months, I’ve also been thinking a lot about the large number of colleagues who worked so hard, day and night. I know a good fraction of them personally, and a few I count as friends. We began more or less together when we were much younger, targeting gamma-ray burst afterglows, and almost twenty years later we’re still here pointing “our” telescopes at a new category of astrophysical sources. We have been a lucky generation of astronomers!

    Links

    Press release: ESO Telescopes Observe First Light from Gravitational Wave Source
    Science Paper: The electromagnetic counterpart to a gravitational wave source unveils a kilonova, by S. J. Smartt et al. in Nature
    Science Paper: The unpolarized macronova associated with the gravitational wave event GW170817, by S. Covino et al. in Nature Astronomy
    LIGO press release

    Biographies

    Stephen Smartt and Stefano Covino

    Stefano Covino is an astronomer with the Istituto Nazionale di Astrofisica (INAF), currently working at Osservatorio Astronomico di Brera. His primary research interests are gamma lightning, gamma ray bursts and high energy astrophysics. He has worked on robotics for telescopes and optical instruments as well as in many foreign institutions.

    Stephen Smartt is Director of the Astrophysics Research Centre at Queen’s University Belfast. His work focuses on superluminous supernovae and the stars that produce them. He is head of the Pan-STARRS Survey for Transients which leads the world’s supernova discoveries, and he is PI and Survey Director of PESSTO, the Public ESO Spectroscopic Survey of Transient Objects.

    See the full article here .

    See also https://sciencesprings.wordpress.com/2017/10/20/from-ucsc-neutron-stars-gravitational-waves-and-all-the-gold-in-the-universe/ for the full story from UCSC.

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

     
  • richardmitnick 3:07 pm on December 22, 2017 Permalink | Reply
    Tags: , , , , ESO’s Collaboration with Industry, ESOblog   

    From ESOblog: “ESO’s Collaboration with Industry” 

    ESO 50 Large

    ESOblog

    22 December 2017

    1
    Letters from the DG, Xavier Barcons

    Greetings!

    In my last “letter” I talked about the huge range of opportunities and benefits available to ESO’s Member States. Today I’d like to elaborate on how we at ESO work with universities, research institutions and leading companies in our Member States to design and build our telescopes and scientific instruments.

    Astronomy is a driving force for humanity, challenging our curious minds and pushing us to make key progress here on Earth and beyond. It’s an inherently innovative discipline, using some of the most advanced technologies and sophisticated techniques available to scientists and engineers, and it constantly urges them to take one step further and come up with creative new solutions.

    2
    A 360 degree panorama view of a rare cloudscape over La Silla, in the southern edges of the Atacama Desert, home of ESO’s first observing site.
    Credit: ESO/F. Kamphues

    In order to carry out its ambitious programme of scientific research, ESO designs, constructs and operates the most advanced ground-based astronomical telescopes in the world. Unsurprisingly, the construction of such major facilities usually takes up to a decade or more. ESO has built its facilities at three observatories in Chile: La Silla, Paranal-Armazones and Chajnantor. Creating infrastructures of this size and complexity requires a massive collaborative effort between scientists, engineers and industry partners across the world. Scientific institutes in Member States participate in these massive projects, promoting and organising collaboration and giving them cutting-edge know-how — but ESO also joins efforts with a wide range of industry partners to bring ambitious projects to life. Companies in Member States can receive contracts from ESO, covering all business areas from the provision of services to technical studies to the delivery of advanced equipment.

    4
    The fourth 8.2-m VLT Zerodur® mirror during the final phase of polishing at REOSC.
    Credit: ESO

    The collaboration between ESO and industry started many years ago. One of the best known examples is the Very Large Telescope (VLT), the most advanced optical/infrared ground-based facility in the world. Back in 1988, ESO signed a contract with the German company SCHOTT to cast the four giant telescope mirror blanks from the specialised material Zerodur®. SCHOTT has now de facto become the main provider of mirror blanks to ESO. In France, a new optical facility was created at Safran Reosc for polishing the giant mirrors for the VLT, and in Italy a consortium of three companies, the AES Consortium, was formed to construct the main mechanical structures of the four 8.2-metre VLT Unit Telescopes. The fruitful VLT collaboration still endures to this day; the recently-installed Adaptive Optics Facility is a triumph of collaboration between ESO and industry.

    In total, over 330 million euros were spent in the ESO Member States for the construction of the VLT. Hundreds of suppliers were involved and more than 70 contracts each exceeding 500 000 euros in value were awarded, covering a wide range of industrial services, from civil works to precision electronics to large-scale glass manufacture.

    Another example of a massive and successful collaborative project is the Atacama Large Millimeter/submillimeter Array (ALMA), a 1.3 billion euro project between ESO, North America, and East Asia.

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    The antennas of the Atacama Large Millimeter/submillimeter Array (ALMA), set against the splendour of the Milky Way
    Credit: ESO/B. Tafreshi (twanight.org)

    ALMA is a giant telescope composed of 66 high-precision antennas; North America provided 25 of these antennas, East Asia 16, and the remaining 25 were provided by ESO. The ESO antennas were manufactured by the European AEM Consortium, led by French, Italian and German companies participating under a nearly 150 million euro contract, one of the largest ever European industrial contracts for ground-based astronomy.

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile, at an altitude 3,046 m (9,993 ft)

    The Extremely Large Telescope (ELT) is ESO’s current major project, with a budget of 1.15 billion euros. This 39-metre optical/infrared telescope will dwarf all other telescopes. ESO signed the contract for the ELT dome and telescope structure with the Italian ACe Consortium, consisting of Astaldi, Cimolai and the nominated sub-contractor EIE Group. This is the largest contract ever awarded by ESO and also the largest contract ever in ground-based astronomy worth an approximate value of 400 million euros. SCHOTT is again casting the telescope’s mirrors, Safran Reosc will polish the mirrors, the SENER Group will supply the mirror cells, and the FAMES consortium — composed of Fogale and Micro-Epsilon — will provide the edge sensors for the 798 hexagonal segments of the primary mirror. Of course, this is not the end of it; there is still a large number of industrial contracts that need to be placed for the ELT, and so further opportunities for European industry will be available in the coming years. Furthermore, the ELT will be equipped with a wide variety of instruments that will be developed and built by our Member States institutes and companies.

    6
    Participants in the ELT contract signature ceremony at ESO Headquarters on 18 January 2017. The picture shows representatives of teams involved, both from SCHOTT, the SENER Group and the FAMES consortium, and from ESO. Credit: ESO/M. Zamani

    _____________________________________________________

    ESO’s projects involve staggering technology and continuous innovation and knowledge gain.
    _____________________________________________________

    But ESO’s telescopes and instruments aren’t the only ones to benefit. ESO’s projects involve staggering technology and continuous innovation and knowledge gain, offering possibilities for technology and knowledge transfer. Since the science and engineering of these huge astronomical projects is cutting-edge, most of it must be developed from scratch — creating opportunities to start new companies, boost high-skilled employment, and generate substantial added value to our Member States’ economies. Companies working for ESO’s demanding projects often need to develop new skills and capacities; these challenges become assets of the companies afterwards, expanding their business opportunities.

    ESO also sets new global benchmarks for size, accuracy, capacity, speed and efficiency of optics, mechanics, sensors, lasers, computing, communication, construction, logistics and other important fields. ESO’s projects offer a clear showcase for industry. They benefit our Member States, our industry partners, the scientific institutes working with us, and even society as a whole. To name just two simple, concrete examples, a broad range of dental treatments stem directly from laser developments in astronomy, and adaptive optics technology in telescopes has been implemented in microscopic techniques to improve resolution and contrasts, as well as in instruments for ophthalmology enabling sharp imaging of the retina.

    7
    Cerro Armazones in the Atacama Desert, near ESO’s Paranal Observatory, at sunset. Cerro Armazones is the selected site for the ELT.
    Credit: ESO/S. Brunier

    See the full article here .

    Please help promote STEM in your local schools.
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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

     
  • richardmitnick 9:51 pm on December 15, 2017 Permalink | Reply
    Tags: , , , , ESOblog, Wind Tunnel Tests: Preparing the ELT for Mountain Life   

    From ESOblog: “Wind Tunnel Tests: Preparing the ELT for Mountain Life” 

    ESO 50 Large

    ESOblog

    1

    The Extremely Large Telescope (ELT) promises to open a whole new chapter in astronomy when it sees first light in 2024, and scientists, engineers, designers and other experts are enthusiastically working to build it. With a dome nearly 74 metres high and 86 metres in diameter, the ELT may be a giant, but it’s also exposed to significant wind. The telescope is being built on top of a 3-km-high mountain — Cerro Armazones in the Atacama Desert — so it is crucial to test how high-altitude winds will affect the telescope and dome. Wind tests on a scaled model are currently being performed in the wind tunnel of the Department of Mechanical Engineering of the Polytechnic University of Milan in Italy, on behalf of the ACe Consortium, which is composed of Astaldi, Cimolai and their nominated subcontractor EIE GROUP, who are building the ELT Dome and Main Structure. Within the ACe Consortium, EIE Group is in charge of the wind tunnel testing for the ELT project. To catch up on the current status of this testing, we talked to engineer and designer Stefano Mian from EIE GROUP, and to Professor Daniele Rocchi and engineer Luca Ronchi of POLIMI, who followed all the wind testing phases.

    Q: So let’s start with the key question — how windy is it on top of Cerro Armazones?

    Stefano Mian (SM): On top of Cerro Armazones, where the ELT will be built, we’ll sometimes have quite windy conditions. To define the design wind speed, a meteorologic analysis was performed of the site where the structure will be built. This study was performed by ESO, who installed anemometers some years ago and recorded the wind speed for a long period of time.

    2
    Maximum wind speed 30 metres above ground performed at Cerro Armazones summit in the period 2010-2013. Credit: ESO.

    The aim is to build a statistical database to estimate the highest level of wind that may occur during the lifetime of the structure since we have to be sure the dome will survive all the wind conditions it might face — right up to the end of its operating life. Even a possible extreme event should be taken into account. This is an event that might occur only once in the whole life of the structure, and usually, it is something we don’t record during the monitoring period but it’s something that can be estimated through statistical analysis.

    The design wind speed is 47 m/s (which is about 170 km/h), during an average time of 10 minutes.


    This ESOcast Light explores how and why engineers are undertaking wind tunnel tests for ESO’s Extremely Large Telescope. Credit: ESO.

    Q: How does the wind test work?

    Luca Ronchi (LR): The wind tunnel test is developed to reproduce the conditions that the ELT will face when it’s operational, so basically it’s about reproducing the dome and telescope on a smaller scale (made of glass-fibre reinforced plastic), equipping it with sensors, calibrating these sensors, placing the object in the wind tunnel, and — according to the established and agreed-upon test programme — reproducing the conditions that the ELT will actually face on top of Cerro Armazones. Then, we have to vary the angle of the incoming wind and to test different configurations of the dome itself.

    Q: How is it possible to test big structures with small-scale models?

    LR: Obviously the problem when testing buildings in a wind tunnel is that they’re simply enormous, so you can’t test them in a 1:1 ratio. That’s why we use reduced-scale models. The data that we acquire then need to be adjusted so they’re applicable to reality. There are coefficients and similarity criteria to be followed, as well as experience that allows us to make the data realistic and reliable to use, even though they were obtained with a scale model in slightly different conditions.

    3
    The ELT model while visiting ESO’s Headquarters in Garching, Germany, for Open House Day 2017. Credit: ESO/P. Horálek

    Q: Is this work similar to building bridges and other big engineering projects?

    Daniele Rocchi (DR): Yes it is — our tests on the ELT are similar to the wind engineering tests that are usually performed for buildings, for example. But the ELT’s structure has some peculiar features. For example, it has two very big sliding doors with a large surface area and a lot of what we call “wind loading” — the amount of pressure against the surface. We also have to protect the telescope from the wind with a porous windscreen when observing through the open doors.

    Q: Before testing the current model, how many different configurations did you try?

    DR: We started with the project several years ago with different designs of the dome and telescope. Now we’re almost at the final stage of the design. For this one we tested several configurations, considering different directions of the incoming wind and also different windscreen porosities because the porosity is one of the key features of the windscreen to protect the telescope.

    6
    Preparing the ELT model to be tested in the wind tunnel. Credit: ESO

    Q: Is there room for creativity in this kind of project?

    SM: One of the main challenges of such a project is to fulfil the thousands of technical requirements. Consequently, one of the most important tasks for the designer is to make sure all requirements are included in the model. Even so, one may think that consequently there is no room left for creativity, but on the contrary, I do think that creativity is the key aspect to finding new solutions that comply with all the requirements.

    Q: What excites you the most about building the ELT Dome and Main Structure?

    DR: As a wind engineer, building the ELT is extremely exciting because this structure is unique in its field. It’s very, very big, and has very large wind loading that has to be taken into account, especially when you have to move its doors under windy conditions.


    Interview with Stefano Mian, Daniele Rocchi and Luca Ronchi about their roles in the wind tunnel testing for the ELT project. Please turn on closed captions for English translations of answers.
    Credit: ESO

    Q: What are the main challenges of wind testing?

    DR: The main challenge of wind tunnel testing is to reproduce a flow around the model of the dome that is similar to the real one. This helps us predict the wind loads on the structure through pressure and force measurements, according to specific scaling rules. In the case of the ELT dome, another major challenge is to design porous windscreens that will protect the telescope during operation from winds of up to 24 m/s, considering both wind loads and thermal aspects.

    Q: What would be the consequences if wind testing wasn’t undertaken?

    SM: The design of a structure must take into account all the loads that can occur (such as wind, snow, earthquakes, and so on). It’s simply a must.

    DR: For standard buildings, these loads can be defined according to prescriptions specified in international or national codes. But for non-standard buildings, like the ELT dome, we have to perform wind testing to define wind loads. Wind loads can lead to the failure of the structure, from the detachment of parts like cladding panels to the full collapse of the main structure!

    7
    Designers and engineers use numerical models to simulate the strength of the model before testing it in practice. Credit: ESO

    Q: After testing the model, what actions are taken by the engineers? Have there already been significant changes based on these tests?

    LR: In general — and this has not been necessary in the case of the ELT — if the results of a wind tunnel test are not satisfactory, it is possible to modify the model and test it again to seek a better performance. If the modified model behaves better than the baseline, we let our clients know and then it’s up to them to amend the first design accordingly. Of course, the goal of a wind tunnel test campaign is to focus on the aerodynamic performance of a model and look for ways to improve it. As the model is representative of the real full-scale object, the design of the real thing should be amended too.

    See the full article here .

    Please help promote STEM in your local schools.
    STEM Icon

    Stem Education Coalition
    Visit ESO in Social Media-

    Facebook

    Twitter

    YouTube

    ESO Bloc Icon

    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

     
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