From ESOblog (EU): “Galactic Archaeology – How we study our home galaxy”

From ESOblog (EU)

At

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

11.4.22

Rebecca Forsberg
Rebecca is a science communication intern at ESO. Prior to this position she has completed a bachelors and masters degree in astronomy & astrophysics, and is currently (when not working at ESO) doing a PhD at Lund Observatory, Sweden. Rebecca found her passion for writing and communicating science as a science reporter for the Swedish magazines Populär Astronomi and Lundagård.

We have imaged millions of galaxies, but we have so far not been able to take an image of our home galaxy as seen from the outside. So, how do we know what it actually looks like? And how it came to be and has evolved? With the combined power of ground- and space-based telescopes, astronomers can map and do archaeological studies of the Milky Way, to unveil its dramatic past, and peer into its future.

The Milky Way. Credit: R. Hurt/The National Aeronautics and Space Agency JPL-Caltech. The bar is visible in this image.

How do we study the galaxy where we live? It’s a bit like being asked to draw a map of the city you live in, without being able to leave your house. You might be able to peer through the windows and see some features like streets and tall buildings, but most will be hidden by nearby houses. It is quite similar when trying to image the Milky Way. Voyager 1, the most distant human-made object, has been traveling for 45 years and is now more than 20 billion kilometres away.

National Aeronautics and Space Administration Voyager 1.

Still, that’s pretty much next door in galactic terms: you would need to be several million times further away to get a clear view of the Milky Way from the outside.

We sit within the Milky Way, and as we look up in the sky we see the hazy stellar band of our galaxy, and clouds of dust obscuring the inner parts of the galaxy, making galactic mapping even harder. Follow along as we draw the map of the Milky Way, starting from the first draft.

A walk down memory lane…

One of the first ever attempts to make a map of the Milky Way was in 1785 by the astronomers, and siblings, Caroline and William Herschel. The Herschels counted the stars they could see in the night sky, and they assumed the galaxy was deeper in the directions where there were more stars. The regions shielded by dust and gas towards the constellation of Sagittarius are already evident in this map, in the white space between the two reaching arms on the right. We now know that this region is the centre of the Milky Way, but back then it was supposed to be one of the edges, as stars to the other side were blocked from our view.

The first map of the Milky Way produced by astronomers Caroline and William Herschel in 1785, with the Sun roughly in the middle. Credit: Caroline Herschel.

We have only known for about 100 years that galaxies outside of the Milky Way exist, but this discovery was not without controversy. In the early 1900, Harlow Shapley measured the distribution of globular clusters – old, massive collections of stars – in the Milky Way. He found them to be in a spherical arrangement around, what he correctly assumed, is the centre of the galaxy. This allowed him to both estimate the actual size of the Milky Way, as well as to place the Sun within it (and it was not in the centre!).

At the same time, Heber Curtis was measuring the optical spectrum of the, at the time, spiral-shaped “Andromeda nebula”, arguing for its resemblance to the Milky Way, leading to his conclusion that there existed galaxies outside of our own.

Andromeda Galaxy (Messier 31). Credit: Adam Evans.

This led to a hefty discussion among astronomers, regarding the status of Andromeda as a galaxy of its own or as a nebulous cloud within the Milky Way. This discussion in 1920 was so pivotal that it has been given the name “The Great Debate”. Even though Shapley argued that nothing could be as large as the Milky Way, the debate was settled in Curtis favor when Edwin Hubble managed to measure the distance to the stars in Andromeda, and concluded them to be 10 times further away than the most distant stars in the Milky Way.

Edwin Hubble at Caltech Palomar Samuel Oschin 48 inch Telescope Credit: Emilio Segre Visual Archives/AIP/SPL.

Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, altitude 1712 m (5617 ft). Credit: Caltech.

This marked the beginning of a new era in astronomical research, recognizing that the observable size of the Universe was much bigger than previously envisioned.

The leap in mapping the Milky Way came in the early 1990s when Lennart Lindegren, together with Michael Perryman and the European Space Agency (ESA), proposed the Gaia space telescope mission, the successor to the Hipparcos mission (1989-1993).

European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganization](EU) GAIA satellite.

European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganization](EU)Hipparcos satellite.

Launched in 2013, the Gaia telescope has provided invaluable information about the appearance of our galaxy.

Early 1950, the astronomer Knut Lundmark commissioned Martin and Tatjana Kesküla to paint a map of our galaxy, known as the Lund Panorama of the Milky Way. By hand, they added the positions of about 7000 individual stars to create an, at the time, unprecedented drawing of the Milky Way. The 2 by 1 -metre map took two years to paint and can still be seen at Lund Observatory, Sweden. Credit: Lund Observatory, Sweden. This image is not under our CC-BY 4.0 license.

How do we map the galaxy?

Gaia is an expert at measuring the position and velocities of the stars, with so far having mapped almost 2 billion stars in the Milky Way, which is still only 1% of all stars in the galaxy. This allows astronomers to trace the structures of the Milky Way. They can also model the motions of the stars into the past as well as into the future, giving clues as to what the galaxy used to look like, and what’s up ahead.

But how can Gaia measure the distance to a star? It does so by observing how the star moves with respect to background stars, using stellar parallax.

Illustration of how the parallax method works. The apparent position of a nearby star as seen from Earth changes as the Earth orbits around the Sun, allowing astronomers to measure the distance to it. Credit: NASA, ESA and A. Feild (STScI)

You can try this yourself by sticking out your finger in front of you, and now close one eye, and then switch. Notice how your finger seems to move with respect to the background. If you move your finger further away, it will appear to move less, or the angle is smaller. For the stars, we can use the same principle, but instead of having our two eyes, we now use Earth’s orbit around the Sun as our two viewing points. Using the angle of the apparent shift and the distance between the Sun and Earth, the distance to the star can be measured.

Galactic archaeologists study the history of our galaxy and the stars in the sky are their fossils, which provide clues to the Milky Way’s past. To do so, astronomers need to measure the chemical fingerprint of stars, which tells astronomers what they are made of, and in turn what the gas cloud they formed from consisted of, giving clues to their age and origin. However, stars tend to move away from their birthplace, making the puzzle much harder to solve. The chemical fingerprint is obtained through spectroscopy, which just so happens to be one of the many areas of expertise of ESO’s telescopes and instruments. Gaia on the other hand excels at tracking stellar positions and motions, which makes the synergy between Gaia and ESO uniquely suited to unravel how our galaxy formed.

The synergy of ESO and Gaia spans many fields. First, ESO keeps track of the Gaia telescope, making sure that it stays where it’s supposed to be in space. Secondly, the Gaia-ESO public survey uses ESO’s facilities to obtain the chemical information of stars tracked by Gaia, with the goal of further unravelling the mystery of the Milky Way.

The Gaia-ESO survey uses the Fibre Large Array Multi Element Spectrograph (FLAMES) on ESO’s Very Large Telescope (VLT) [below] based in ESO’s Paranal site in the Chilean desert.

European Southern Observatory(EU) FLAMES on The ESO Very Large Telescope, Cerro Paranal, Chile. FLAMES is the multi-object, intermediate and high resolution spectrograph of the VLT. Mounted at UT2, FLAMES can access targets over a field of view 25 arcmin in diameter. FLAMES feeds two different spectrograph covering the whole visual spectral range: GIRAFFE and UVES.

This instrument allows astronomers to gather spectra for more than 100 stars simultaneously, thanks to optical fibres that are carefully arranged by a robot at the locations of the target stars. Over the course of 6 years the Gaia-ESO survey collected spectra for over 100 000 stars. The science output from this survey is immense; at the time of writing close to 200 studies have been published using Gaia-ESO data. A more thorough background on Gaia-ESO can be found in this previous blog post, but for now, let’s go deeper into the Milky Way and see what we can learn about its history with the help of Gaia-ESO.

Building the Milky Way

In simplified terms, to build a galaxy, we first need gas and dark matter. Thanks to gravity, the gas will collapse into stars, which are gravitationally bound and swirl together creating a galaxy. Over time, the galaxy will change and evolve, partly due to the evolution of the stars themselves. During their lifetime, stars fuse hydrogen and helium into heavier elements that are then expelled into the surrounding gas. Subsequent generations of stars that form out of that enriched gas will incorporate those heavy elements into their composition. By studying the chemical fingerprints of the stars, we can then distinguish their different generations.

The Milky Way is a spiral galaxy, with a disc that has well-defined spiral arms and a puffed up region in the middle called the bulge. The disc and bulge are embedded in a halo that contains globular stellar clusters and dark matter.

Caterpillar Project A Milky Way size Dark Matter halo and its subhalos circled, an enormous suite of simulations. Griffen et al. 2016.

However, this is a very broad and simplified description of our home galaxy. Did you know that the Milky Way disc actually consists of two discs? These were discovered in the early 80’s when astronomers started counting the stars in the Milky Way, finding two discs camouflaging as one, with different thickness and densities, giving them the names the “thick” and the “thin” disc. They kind of look like a sandwich, with the thin disc in the middle. Over time, thanks in part to the Gaia-ESO survey, it has been found that the discs can be separated both in age and in chemistry. The thick disc has been shown to be 9 billion years older than its thin counterpart and also has less heavy elements. Also, the thin disc is rich in gas and dust, whereas the thick disc contains mostly stars.

Gaia’s all-sky view of our Milky Way Galaxy and neighboring galaxies, based on measurements of nearly 1.7 billion stars. The map shows the total brightness and colour of stars observed by the ESA satellite in each portion of the sky between July 2014 and May 2016.

Brighter regions indicate denser concentrations of especially bright stars, while darker regions correspond to patches of the sky where fewer bright stars are observed. The colour representation is obtained by combining the total amount of light with the amount of blue and red light recorded by Gaia in each patch of the sky.

The bright horizontal structure that dominates the image is the Galactic plane, the flattened disc that hosts most of the stars in our home Galaxy. In the middle of the image, the Galactic centre appears vivid and teeming with stars.

More information on: http://sci.esa.int/gaia/60169-gaia-s-sky-in-colour/

Credit: ESA/Gaia/DPAC

A violent past, present and future – hold on tight!

Artist´s impression of the star and dust tail from the torn-to-pieces Sagittarius dwarf galaxy, currently being engulfed by the Milky Way. Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

Now, where do these two discs come from? Astronomers believe that they’re the result of the Milky Way having engulfed old galaxies in the past.

Sometimes galaxies pass right through each other, producing ring-like structures, or tearing each other apart whilst merging into larger systems. The Milky Way hasn’t undergone such major interaction with a similarly large galaxy, but it has gobbled smaller ones, whose remnants can be observed in the discs and halo of the Milky Way.

By studying the motion and chemical makeup of stars in the Milky Way, astronomers found the scattered remains of an old engulfed galaxy that had been torn to pieces several billion years ago, and whose stars are now part of the thick disc of the Milky Way. But the thick disc is not the only graveyard of past accreted galaxies: in the halo of the Milky Way astronomers have also found remnants of several digested galaxies. All these infalling galaxies have thus participated in the evolution and shaping of our home.

However, that’s not the end of the Milky Way’s hectic history. Actually, our galaxy is in the process of engulfing another galaxy right now: the dwarf galaxy Sagittarius. The Sagittarius galaxy has been passing through into our galaxy several times, being torn apart by the gravity of the Milky Way more and more for every passing. Just like throwing a rock in water, the repeated plunges of Sagittarius into the Milky Way have created ripples in the overall disc of the Milky Way, making stars move up and down, which can be seen by Gaia.

Fast forward four billion years into the future, and it is anticipated that the Milky Way and its closest large neighbour, the Andromeda galaxy, will merge, creating a new galaxy.

Milkdromeda with Andromeda on the left-Earth’s night sky in 3.75 billion years. No one will be here on Earth to see it. Maybe humans will have escaped the Sun’s becoming a Red Giant and observe it from a new home. Credit: The National Aeronautics and Space Agency.

Yet again, our galaxy will be reshaped, and over time the stars of the two galaxies will mix, forming a new type of galaxy, an elliptical.

The full picture?

So, have we obtained our final map of the Milky Way? Well, we are getting there! Thanks to targeted surveys, like Gaia-ESO, the galaxy is being uncovered more and more, and we now have a rather detailed idea of its spiral arms and the strange features of the discs. However, just as drawing a map of your city from your house, it can be particularly hard to study the busiest regions, like the central ones. In the Milky Way’s case, our view towards the centre is covered with dust clouds blocking the light. But thanks to infrared- and radio detectors it is possible to peer through the dust. These detectors have allowed us to take an image of Sagittarius A*, the supermassive black hole, at the centre of our galaxy and, by measuring the motion of nearby stars, determine its mass to be equal to 4 billion Suns.

This is the first image of Sagittarius A* – the supermassive black hole at the center of the Milky Way. Credit: EHT Collaboration.

In the future Gaia will be joined by two upcoming instruments at ESO’s Paranal Observatory: MOONS at the VLT and 4MOST at the VISTA telescope. These will be able to capture infrared and visible spectra of over 1000 objects at the same time, allowing astronomers to obtain the chemical fingerprint of millions of stars. Together with Gaia, these two new instruments will dig out many of the secrets that the Milky Way holds, so that one day we may have a complete map of our galaxy.

See the full article here .

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European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU) 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: Cerro 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”.

European Southern Observatory(EU) La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun).

ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE) 2.2 meter telescope at/European Southern Observatory(EU) Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) La Silla Observatory 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) , Very Large Telescope at Cerro Paranal in the Atacama Desert •ANTU (UT1; The Sun ) •KUEYEN (UT2; The Moon ) •MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). Elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

ESO Paranal Residencia

ESO Paranal Residencia inside near the swimming pool

ESO Paranal Residencia dining room

European Southern Observatory(EU)VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, •ANTU (UT1; The Sun ),•KUEYEN (UT2; The Moon ),•MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening.

ESO VLT Survey telescope.

ESO Very Large Telescope 4 lasers on Yepun (CL)

Glistening against the awesome backdrop of the night sky above ESO’s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system.

ESO New Technology Telescope at Cerro La Silla , Chile, at an altitude of 2400 metres.

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL) Danish 1.54 meter telescope at La Silla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

The Leiden Observatory [Sterrewacht Leiden](NL) MASCARA instrument cabinet at 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 telescopes, an array of twelve robotic 20-centimetre telescopes at Cerro Paranal,(CL) 2,635 metres (8,645 ft) above sea level.

ESO Speculoos telescopes four 1 meter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level.

TAROT telescope at Cerro LaSilla, 2,635 metres (8,645 ft) above sea level.

European Southern Observatory (EU) ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres.

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. A large project known as the Čerenkov Telescope Array composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile at, ESO Cerro Paranal site The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the. University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), The new Test-Bed Telescope 2 is housed inside the shiny white dome shown in this picture, at ESO’s LaSilla Facility in Chile. The telescope has now started operations and will assist its northern-hemisphere twin in protecting us from potentially hazardous, near-Earth objects.The domes of ESO’s 0.5 m and the Danish 0.5 m telescopes are visible in the background of this image.

Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) The open dome of The black telescope structure of the‘s Test-Bed Telescope 2 peers out of its open dome in front of the rolling desert landscape. The telescope is located at ESO’s La Silla Observatory, which sits at a 2400 metre altitude in the Chilean Atacama desert.

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL) Danish 1.54 meter telescope at La Silla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

 

From ESOblog (EU): “Training the astronomers of the future”

From ESOblog (EU)

At

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

9.9.22
People@ESO

Rebecca Forsberg
Rebecca is a science communication intern at ESO. Prior to this position she has completed a bachelors and masters degree in astronomy & astrophysics, and is currently (when not working at ESO) doing a PhD at Lund Observatory, Sweden. Rebecca found her passion for writing and communicating science as a science reporter for the Swedish magazines Populär Astronomi and Lundagård.

As in previous years, this summer several university students were invited to conduct a research project at ESO’s Headquarters in Garching, Germany. Besides the projects, the six-week long Summer Research Programme included a series of lectures, covering everything from how telescopes work and Deep Learning, to the building blocks of exoplanets and X-ray binaries. They also visited the ESO Supernova Planetarium & Visitor Centre, and got to experience everyday life at ESO.

We took the opportunity to talk to the students after their projects were done and they had presented them to the members of staff at ESO. Follow along as we chat about their expectations, the work environment at ESO, their research projects, and what is waiting for them now.
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Name: Natanael Gomes de Oliveira
Nationality: Brazilian
University: Federal University of Rio de Janeiro
Project: Wind-blown bubbles around accreting neutron stars and black holes
Advisors: Marianne Heida & María Díaz Trigo

“My project at ESO was about X-ray binaries –– systems where a normal star orbits a compact object like a neutron star or a black hole that steals material from its companion. In particular, I studied bubbles blown by the wind from the accretion disc of these objects. The research I’ve been doing previously at my home university was quite different, so this project was a bit challenging for me, but it also means that I have learned a lot of new stuff, which is great! For instance, I learned to reduce spectra on my own, which is very useful for my area of research.

I analyzed data from the FORS2 instrument on the Very Large Telescope (VLT)[below], and found that one of our objects has clear signs of the presence of a wind-blown bubble.

The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL) FORS2 mounted on the VLT Telescope Unit 1 (Antu).

We hope to confirm this result soon, and if so, this will be the first bubble caused by accretion-disc winds in an X-ray binary in the Milky Way, which is a great result!

Working at a top institute in the world is every young scientist’s dream, and it is no different with me. I have always wanted to know what day-to-day life is like for professional scientists, so the summer programme, and the opportunity to get to know people from all over the world, suited me like a glove.

I will never forget the Science Social Day when we went hiking in the mountains and tried to discover a “fun fact” about each person, that was really fun. To be honest, I have no words to describe how grateful I am to ESO for the whole experience, and to every single person I have met throughout the summer programme. Now I plan to start my masters, and after that I would love to go back to ESO to do my PhD, hopefully.”
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Nicolás Guerra.

Name: Nicolás Guerra
Nationality: Chilean
University: University of Chile, Santiago
Project: Changing monsters: How do blazars change their power across the spectrum?
Advisors: Paula Sánchez-Sáez, Gabriela Calistro Rivera & Martin Zwaan

“The programme was an incredible opportunity to go out of my comfort zone and conduct research in a new place and to meet new people. I had never worked outside of the University of Chile, and it was truly an incredible experience.

As for my project, I worked on active galaxies. These have an accreting supermassive black hole in their centre, which produces relativistic jets. We call it a ‘blazar’ when the jet is pointing straight at the Earth. Blazars undergo extreme variations in their brightness, and we don’t really understand how and why.

During the project, I studied how the light from blazars varies, and found that the variability in visible light is followed by variability in radio after some delay! This can help to further understand the physics of blazars, as well as making radio calibrations with ALMA [below] more precise, as blazars are often used as calibrators for other observations

Besides the project and my supervisors being great, the work environment was very active and engaging, with a journal club, science coffees and talks, and it was truly amazing to be amongst people who were just as excited about astronomy as I am! For instance, watching the release of the first images from the James Webb Space Telescope together at ESO was a really memorable experience!

To work at ESO was everything I expected it to be and more! I have learnt about what doing scientific research is like, and I’ll definitely benefit from it in future research opportunities. I learned how to use a number of data analysis tools, interpret ambiguous graphs, and to think about a physical reason to explain the results I saw.”
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Name: Sophie Penger
Nationality: German
University: University of Cologne
Project: Extragalactic planetary nebulae in the central regions of galaxies
Advisors: Magda Arnaboldi (ESO) & Johanna Hartke (Oxford)

“During my bachelor’s thesis, I found my main research interest to be galaxies and integral field spectroscopy. As such, having worked with data from ESO instruments before with great joy, I was very curious about the work that takes place at ESO Headquarters. The project I ended up doing was a good match to my previous research. Not only did it require me to bring in some of the techniques I acquired before the programme, but also allowed me to broaden my knowledge on the topic with many new skills obtained from experts at ESO.

In this project, I looked at the interaction of two galaxies: the dwarf galaxy VCC 1249 and a bigger galaxy: Messier 49. I got to use data from the MUSE instrument in the VLT to trace planetary nebulae in the galaxies.

European Southern Observatory(EU) MUSE on Yepun (UT4) on the Very Large Telescope, Cerro Paranal (CL)

I managed to find several planetary nebulae candidates in and around the dwarf galaxy that, if confirmed, might bring conclusions on possible nebulae that have been stripped from the dwarf galaxy.

I really enjoyed the feeling of being a part of the ESO community and being met as equals. We were trusted to work on exciting projects independently, whilst being well supported by our supervisors if needed. It was very enriching to be included in numerous activities that take place at ESO and talk to many people from different research topics.

Even though the six weeks are already over, I hope to stay in contact with my supervisors and make further investigations of the data whilst finishing my masters degree and applying for PhD programmes in astronomy. I can highly recommend anyone who is interested in a career in astronomy to apply for the ESO Summer Research Programme. It helped me so much with my plans for my scientific future, and to gain both new research skills and confidence in my abilities.”
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Name: Isabel Kerr
Nationality: British
University: University of St Andrews
Project: Hide and seek with brawling stellar couples
Advisors: Julia Bodensteiner, Jakub Klencki & Henri Boffin

“In my project I analyzed spectra taken by MUSE [above] in order to identify binary systems, stars in couples, within a specific stellar cluster (I found 3!). Then I considered theoretical models to conclude possible formation scenarios of the identified binary systems. One of the systems is likely a stripped star that has lost its outer layers accompanied by a disk-bearing secondary which is an exciting discovery!

Having graduated from my masters in astrophysics only three weeks before coming to ESO, I had recently done some research for my thesis looking at the frequency of protoplanetary discs around young stellar binaries. As such, I chose the ESO project because I’ve always had a keen interest in binary stars and therefore the chance to explore these further was not one to miss.

Besides the project, I wanted to get experience working within an international community, and it was great to meet lots of new people and be part of an active research environment, being able to get involved in daily science coffees and the weekly journal club. Everyone was very friendly and welcoming, and the students of ESO included us in many social activities such as bouldering and hiking!

Now that I am leaving ESO, I am actually going to stay in Germany to teach English in Berlin for a year. But after having such a great experience participating in this programme, I‘ve decided I will look into astronomy PhD opportunities after I‘ve completed my placement in Berlin.”
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Name: Linn Friis-Liby
Nationality: Swedish
University: Luleå University of Technology
Project: Combat stellar activity in the hunt for young planets
Advisors: Louise Dyregaard Nielsen

“I have a background in Mechanical Engineering and am currently pursuing a Masters in Space Science and Technology. During the final year of my masters my focus has shifted to astronomy and the motivation for applying to this programme was to get more insight into the workings of academia, especially at an organization of ESO’s calibre. I was also very excited about learning about a topic in exoplanets that interested me greatly.

The aim of my project was to try and search for planets using the radial velocity method.

Radial velocity Image via SuperWasp.

Radial Velocity Method-Las Cumbres Observatory, a network of astronomical observatories, located at both northern and southern hemisphere sites distributed in longitude around the Earth.

The radial velocity method to detect exoplanet is based on the detection of variations in the velocity of the central star, due to the changing direction of the gravitational pull from an (unseen) exoplanet as it orbits the star. When the star moves towards us, its spectrum is blueshifted, while it is redshifted when it moves away from us. By regularly looking at the spectrum of a star – and so, measure its velocity – one can see if it moves periodically due to the influence of a companion.Credit: The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

I’ve done this by studying how stellar activity in young stars affects their spectra and how this depends on wavelength. Doing so, we can reduce the noise originating from stellar activity, and actually distinguish it from a planetary signal. To do so, I used data from ESPRESSO, a high-resolution spectrograph on the VLT.

ESPRESSO — the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations. ESPRESSO will use the light from any one, or all four, of the Unit Telescopes of the Very large Telescope to extend our capability to find planets around other stars and to measure the fundamental constants of physics.

Espresso Layout

ESO/ESPRESSO on the VLT installed at the incoherent combined Coudé facility of the VLT. It is an ultra-stable fibre-fed échelle high-resolution spectrograph (R~140,000, 190,000, or 70,000) which collects the light from either a single UT or the four UTs simultaneously via the so-called UT Coudé trains.

The end result was a good framework for measuring the wavelength dependency of stellar activity, which can be further expanded upon in the future.

Even though the project itself was everything I could have asked for and more, the people at ESO made this a truly wonderful experience. To be part of the scientific discussions, seminars and social gatherings surrounding this organization has been truly great. Being welcomed into the group and joining all fun activities has generated too many heartwarming memories to count. We explored Munich and enjoyed hikes.

This programme has already and will continue to benefit me. To experience ESO first-hand has taught me a lot about academia and research as a career path. I hope to be able to collaborate with ESO in some way in the future. For now, I will start as a Young Graduate Trainee at The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), combining my engineering experience with my academic interest at another great organization.”
______________________________________________________

Name: Maja Jabłońska
Nationality: Polish
University: Astronomical Observatory, University of Warsaw
Project: Learning the secret of the elixir of youth: a study of blue stragglers with Gaia
Advisors: Henri Boffin & Nicola Gentile Fusillo

“My project was very exciting, as I used the newest data from ESA’s Gaia space telescope, containing measurements of positions and motions for almost two billion sources in the Milky Way with unprecedented precision.

European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganisation](EU) GAIA satellite.

Having this kind of brand-new data I studied stellar clusters, and especially I looked at a somewhat strange type of star – blue stragglers, that are too blue, hot and luminous compared to the rest of the cluster members. One possible explanation could be a mass transfer from a stellar companion. With the Gaia data, I could verify previously reported open cluster data and discover some possible new blue straggler members (or prove some of them aren’t members of those clusters, due to poorer precision of earlier measurements!).

If I was asked to pick the best part of the programme, I am not sure I could! Everything was amazing, even if you study this every day: the high level of science presented, the number of seminars and lectures taking place, the welcoming kind people, visiting the ESO Supernova… This has truly been one of the best experiences I have ever had, I am sad it’s already over!

I already feel I have benefitted from this programme a lot. I used to be quite scared by the thought of being away from home, but after meeting so many lovely, like-minded students I now know that scientific institutions are also great places to meet new friends. Of course, I have also learned a lot and gained new skills, and I am sure I want to continue working in astronomy! Although it’s difficult to choose one subfield as everything is so fascinating, especially after listening to so many great lectures.”
______________________________________________________

See the full article here .

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European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU) 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: Cerro 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”.

European Southern Observatory(EU) La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun).

ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE) 2.2 meter telescope at/European Southern Observatory(EU) Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) La Silla Observatory 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) , Very Large Telescope at Cerro Paranal in the Atacama Desert •ANTU (UT1; The Sun ) •KUEYEN (UT2; The Moon ) •MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). Elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

ESO Paranal Residencia

ESO Paranal Residencia inside near the swimming pool

ESO Paranal Residencia dining room

European Southern Observatory(EU)VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, •ANTU (UT1; The Sun ),•KUEYEN (UT2; The Moon ),•MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening.

ESO VLT Survey telescope.

ESO Very Large Telescope 4 lasers on Yepun (CL)

Glistening against the awesome backdrop of the night sky above ESO’s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system.

ESO New Technology Telescope at Cerro La Silla , Chile, at an altitude of 2400 metres.

Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

The Leiden Observatory [Sterrewacht Leiden](NL) MASCARA instrument cabinet at 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 telescopes, an array of twelve robotic 20-centimetre telescopes at Cerro Paranal,(CL) 2,635 metres (8,645 ft) above sea level.

ESO Speculoos telescopes four 1 meter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level.

TAROT telescope at Cerro LaSilla, 2,635 metres (8,645 ft) above sea level.

European Southern Observatory (EU) ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres.

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. A large project known as the Čerenkov Telescope Array composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile at, ESO Cerro Paranal site The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the. University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), The new Test-Bed Telescope 2 is housed inside the shiny white dome shown in this picture, at ESO’s LaSilla Facility in Chile. The telescope has now started operations and will assist its northern-hemisphere twin in protecting us from potentially hazardous, near-Earth objects.The domes of ESO’s 0.5 m and the Danish 0.5 m telescopes are visible in the background of this image.

Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) The open dome of The black telescope structure of the‘s Test-Bed Telescope 2 peers out of its open dome in front of the rolling desert landscape. The telescope is located at ESO’s La Silla Observatory, which sits at a 2400 metre altitude in the Chilean Atacama desert.

From ESOblog (EU): “Communicating Science at ESO”

From ESOblog (EU)

At

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

8.26.22
People@ESO

Rebecca Forsberg.
Rebecca is a science communication intern at ESO. Prior to this position she has completed a bachelors and masters degree in astronomy & astrophysics, and is currently (when not working at ESO) doing a PhD at Lund Observatory, Sweden. Rebecca found her passion for writing and communicating science as a science reporter for the Swedish magazines Populär Astronomi and Lundagård.

Have you ever wondered who writes ESO’s press releases, comes up with the image captions, scripts the videos and checks on social media activities? Perhaps you, too, are interested in science communication? Meet some of the people behind the texts: the Science Communication interns at ESO’s Department of Communication.

The Science Communication Internship programme, also known as the Science Journalism Internship programme, started with work placements in the early 2000s in what was then the ESO Public Affairs Department. Anna-Lynn Wegener, the current Head of ESO’s Department of Communication, joined as one of our very first interns in 2005. Since then, over 60 interns from all over the world have worked at ESO, and some are now part of the communications team at ESO.

All interns strive to bring the mysteries of the Universe closer to the public and have a passion for writing about science. This aptitude has brought several aspiring science communicators to the Science Communication Internship at ESO.

Actually, the person writing this blog post is one of them (hello!) and we aren’t perhaps as anonymous as I make it sound: sometimes we write for this blog, where we get to either dive into the details of astronomical research, or interview the people behind the science and the telescopes. Here I’ve had the pleasure to talk with some of my predecessors, about their experiences as interns at ESO, their background and favourite tasks, and take a look at where they are today.

A longing to learn and reaching out

Giulio Mazzolo, Science Communication intern from May 2021 to November 2021.
Credit: Giulio Mazzolo.

“I knew I would meet brilliant people and have the chance to learn a lot from each of them, and this was indeed what happened!” says Giulio Mazzolo, who did the internship in 2021. Originally from Italy, Giulio already had a PhD in astrophysics and some expertise in science communication, but wanted to gain experience specifically in astronomy communication. With ESO being one of the world’s leading institutions in astronomical research, Giulio felt like it was an unmatched opportunity to gain experience.

Vanessa Okafor, Science Communication intern at ESO in 2019.
Credit: Vanessa Okafor.

Vanessa Okafor from the UK had a somewhat similar background with a degree in physics and previous experience with communicating science verbally at the Royal Observatory in Greenwich, London. Her longing to grasp the pen to explain the Universe brought her to ESO: “the internship was more writing-focused, so I feel like it made me a well-rounded science communicator and really improved my writing skills”.

Mathieu Isidro during the ALMA inauguration ceremony in March 2013. After his internship, Mathieu worked for over a year with communications for ESO in Chile.
Credit: Mathieu Isidro.

Having science communicators of different backgrounds and experience is key to bring a diverse view, and ESO welcomes interns without degrees in astronomy. This was the case for French-Australian Mathieu Isidro, who prior to his internship in 2012 had a background in language and communications.

“I’d been an enthusiastic amateur astronomer from a young age, which is how I knew of ESO and its telescopes in Chile. I was getting near the end of my studies in language and communication and I really wanted to work in a multicultural workplace doing cutting-edge science – ESO was a perfect match!” says Mathieu.

But the road to the internship was not a straight path for Mathieu, and it was only on his third time applying that he got offered the internship: “I like to joke that ESO finally gave up and had enough of seeing my CV, but it just goes to show that if you really want something you shouldn’t give up and that you should keep learning and growing to get there”.

Thea Elvin, Science Communication intern from March 2021 to August 2021.
Credit: Thea Elvin.

Similarly, Thea Elvin from the UK did not have an astronomy background, but joined ESO with a masters degree in Climate and Atmospheric Science: “science communication was something I enjoyed and the ESO internship seemed like the ideal opportunity to gain some experience.”

What do you actually do as an intern?

Interns do a little bit of everything related to communication, such as writing drafts to many of the texts published by ESO. “Being able to explain difficult concepts in simple language is an important part of the job of an ESO intern and putting this into practice by writing press releases, pictures of the week, and blog posts really helped me take my existing writing skills to the next level”, Thea says. On top of the tasks Thea mentions, the interns also get experience captioning images, writing announcements and scripts for explainer videos, partaking in various meetings, working with the social media team and keeping statistics on ESO’s coverage in news.

With such an assortment of tasks and things to learn, there are various ones that end up being the interns’ favourites. For instance, Vanessa enjoyed the morning routine of checking that the webcams at the observatories were online –– ”Some days the sunrise and sunsets were so beautiful!”, she says –– and interviewing staff for blog posts.

Many of us have a special place in our hearts for the ESOBlog. ”I really enjoyed the creative freedom in terms of writing style and story angle to follow”, says Giulio, and remembers back to all members of staff and astronomers whom he got to interview when working on texts for the blog.

Due to the Covid-19 pandemic, Thea ended up doing her internship remotely[1], but even so she felt like she got the ESO experience: “the whole team was fantastic at making me feel welcome and involved, even from a distance! Learning from the other professionals at ESO was always fascinating – such as learning about storytelling from the Head of the Creative Team, Martin Wallner!”.

Behind the press releases

The press releases are one of the key science communication products at ESO. Scientists will send us their papers and it is up to the ESO News Team, consisting of communicators and scientists, to decide if the research should be featured or not, and how best to highlight it. The interns are part of this process: they give their views on whether they think a paper could be interesting for the media or the public during the ESO News Team discussion, and they draft the release text. Reading scientific papers can be a bit intimidating, even with having a science background like Thea: “my background definitely helped when starting the internship but I didn’t have much experience studying anything astronomy-related, so reading through some of the scientific papers to review for press release was a steep learning curve!”

But once Thea overcame the learning curve, she was greeted with the joy of seeing her pieces featured in various media news outlets. “I’ve been an avid New Scientist reader since I was 16 so it blew my mind to see a story that I had helped to break being covered in there. I wish I could go back in time and show my 16-year-old self because it would have blown her mind too!”

Mathieu, too, had a thrilling moment related to a press release, when he got to interview one of his long-spanning inspirations: “A few weeks into my internship I got to work on my first press release about a major exoplanet discovery by Michel Mayor and his team. I couldn’t believe it! His discovery of the first exoplanet orbiting a sun-like star in 1995 was one of the main reasons behind my passion for astronomy growing up. I got to interview him over the phone, and in a true fanboy moment, told him he was the reason I was there!”.

Golden moments from the everyday life at ESO

Besides producing texts and getting experience in media activities, the internship takes place at a central hub for astronomical research, the ESO Headquarters near Munich, Germany. As an intern, you get access to the weekly seminars, journal clubs, and the everyday social life at Headquarters. One of Giulio’s fondest memories is when members of the communications team went stargazing, admiring shooting stars, which turned out to be ”a lovely evening made of great chats, good food, and some wishes for the future!”.

Vanessa even took the initiative to start a sci-fi movie club, much enjoyed by the students at ESO, and by the end of her stay, the communications team and others at ESO got together for an informal goodbye: “the entire internship gave me some of my favourite memories”.

The operations of ESO’s Department of Communication where the interns work, takes place at ESO Headquarters in Garching, Germany. Credit: Roland Halbe/ESO.

Where are they now?

The internship is a stepping stone for longer-term positions, and interns value the experience and expertise they gain on the job, applying it as they move forward in their careers. Vanessa is currently studying towards a PhD in exoplanets at the University of Warwick, and brought with her many important skills obtained during the internship: “I think the independence I got as an intern and the useful skills such as time management and writing are definitely things I still implement in my daily life”.

Learning how to distill scientific results into press releases is something Thea uses in her day-to-day work as a press officer for the medical journal The Lancet. “When the process for selecting papers to press release was being explained to me, I was relieved to find it was similar to the process at ESO – it helped me quickly go from being quite nervous to thinking ‘I’ve done this before, I can do it again!’”.

As for Giulio and Mathieu, they now have careers related to science communication. Giulio currently manages the support office of ESA Copernicus, the satellite constellation of the Earth Observation programme of the European Space Agency and is an associate editor at astroEDU. Mathieu is the Communication & Outreach Manager for The Square Kilometre Array Observatory (SKAO) collaboration.

And to wrap up this trip down memory lane, Giulio sends a message: “I would like to encourage any astronomy enthusiasts willing to pursue a career in science communication to apply for this internship. For me, it has been an invaluable learning and personal experience, which I totally recommend”.

The basics and how to apply

The internships, which have a duration of six months, are paid. ESO offers a monthly allowance and pays for accommodation (rent and bills) in a shared apartment near ESO’s headquarters. ESO also covers the costs of a return flight from/to the intern’s home station. You can find all the details under the “Internships: Science Journalism” job ad on ESO’s recruitment page. The deadline is always set to the end of the year, but you can send in the application whenever suitable for you, and the Department of Communication will go through your application at the earliest possible time. In the coming months, we plan to recruit for internships starting in 2023.

For additional perspectives from students and fellows at ESO, check out the links below.
Notes

[1] Remote or hybrid internships are not possible in normal times, but as Thea was an intern during the covid-19 pandemic, she could not do her internship on site due to travel restrictions.

Links

Studentships at ESO – Meet our PhD students
Fellowships at ESO – Hands-on experience at world-class observatories

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

Visit ESO (EU) in Social Media-

Facebook

Twitter

YouTube

European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU) 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: Cerro 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”.

European Southern Observatory(EU) La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun).

ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE) 2.2 meter telescope at/European Southern Observatory(EU) Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) La Silla Observatory 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) , Very Large Telescope at Cerro Paranal in the Atacama Desert •ANTU (UT1; The Sun ) •KUEYEN (UT2; The Moon ) •MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). Elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

ESO Paranal Residencia

ESO Paranal Residencia inside near the swimming pool

ESO Paranal Residencia dining room

European Southern Observatory(EU)VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, •ANTU (UT1; The Sun ),•KUEYEN (UT2; The Moon ),•MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening.

ESO VLT Survey telescope.

ESO Very Large Telescope 4 lasers on Yepun (CL)

Glistening against the awesome backdrop of the night sky above ESO’s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system.

ESO New Technology Telescope at Cerro La Silla , Chile, at an altitude of 2400 metres.

Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

The Leiden Observatory [Sterrewacht Leiden](NL) MASCARA instrument cabinet at 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 telescopes, an array of twelve robotic 20-centimetre telescopes at Cerro Paranal,(CL) 2,635 metres (8,645 ft) above sea level.

ESO Speculoos telescopes four 1 meter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level.

TAROT telescope at Cerro LaSilla, 2,635 metres (8,645 ft) above sea level.

European Southern Observatory (EU) ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres.

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. A large project known as the Čerenkov Telescope Array composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile at, ESO Cerro Paranal site The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the. University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), The new Test-Bed Telescope 2 is housed inside the shiny white dome shown in this picture, at ESO’s LaSilla Facility in Chile. The telescope has now started operations and will assist its northern-hemisphere twin in protecting us from potentially hazardous, near-Earth objects.The domes of ESO’s 0.5 m and the Danish 0.5 m telescopes are visible in the background of this image.

Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) The open dome of The black telescope structure of the‘s Test-Bed Telescope 2 peers out of its open dome in front of the rolling desert landscape. The telescope is located at ESO’s La Silla Observatory, which sits at a 2400 metre altitude in the Chilean Atacama desert.

From ESOblog (EU): “We are all stardust”

From ESOblog (EU)

At

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

8.12.22
Rebecca Forsberg

Rebecca Forsberg
Rebecca is a science journalism intern at ESO. Prior to this position she has completed a bachelors and masters degree in astronomy & astrophysics, and is currently (when not working at ESO) doing a PhD at Lund Observatory, Sweden. Rebecca found her passion for writing and communicating science as a science reporter for the Swedish magazines Populär Astronomi and Lundagård.

Science Snapshots

Stars evolve over time. Depending on their mass they live different lives and their deaths differ dramatically. This illustration depicts several of these paths. All stars are formed in gas clouds. Low-mass stars (seen on the top left) evolve slowly. Eventually they eject their outer layers as planetary nebulae. This material can be recycled to form new generations of stars. The remaining core of the star becomes a white dwarf and later a black dwarf. Massive stars (seen on the top right) evolve faster and often end their life in dramatic supernovae explosions. Depending on the mass, it becomes a neutron star or a black hole. Credit: ESO/M. Kornmesser

In the beginning of the Universe, there was only hydrogen and helium, the very lightest of the elements in the periodic table (and a bit of lithium, but that is a story of its own).

Periodic Table from International Union of Pure and Applied Chemistry 2019.

As such, the first generation of stars formed from cosmic gas clouds consisting more or less only of these two elements. All of the other heavier elements, like the oxygen we breathe and the carbon in our bodies, have been formed in various processes involving stars.

University of California-Santa Cruz “All the Gold in the Universe”.

But before we go into that, let’s take a closer look at how stars are formed.

The birth of a star

The space between stars is not always totally empty: gas clouds, the birth chamber of stars, can be found here.

The gas clouds can start to cool, causing them to contract, creating clumpy, dense regions. These regions will accrete more and more, until they reach sufficient mass for the gas to begin collapsing, releasing its own gravitational energy in the process. The material at the centre begins to heat up as a result; as the density, temperature and pressure increase, the material will start to condense into a ball of super hot gas: a protostar is born!

Now, the protostar is not an actual star yet. For that, it needs to start fusing hydrogen into helium (this process is often referred to as burning, but it’s not entirely correct, as explained in a previous blog). To begin hydrogen fusion, the protostar needs to reach a core temperature of millions of degrees. For this, a large gravitational pressure is required, only achievable if the protostar has at least 8% of the Sun’s mass. If the hot ball of gas fails to gather that much mass, it will never start to fuse its hydrogen, and ends up as a brown dwarf [1].

Once the protostar depletes its surroundings from the infalling gas, which can take a few 100 000 years, it will have gathered enough mass to start fusion in its core. At the onset of fusion, the star leaves its protostar stage and (skipping any sort of child- and teenage phases) enters what will be a majority of its life—the main sequence .

Here it should be mentioned that many stars are born and found in pairs, known as binaries, and about one third of all stellar systems [eso1230] contain more than one star. Even though this story is about the life of single stars, it is worthwhile remembering that stars with companions can strongly influence each other’s evolution [eso1540], where one of them might steal material from the other, causing its own evolution to speed up. But that, too, is a story for another day.

The middle ages

The name “main sequence” originates from the diagram that truly is astronomers’ bread and butter: the Hertzprung-Russel diagram (or HR diagram, for short).

Hertzsprung–Russell diagram. A plot of luminosity (absolute magnitude) against the colour of the stars ranging from the high-temperature blue-white stars on the left side of the diagram to the low temperature red stars on the right side.

This diagram shows the evolutionary stages of stars, and naturally we will be coming back to it a lot!

The HR diagram shows the relation between stars’ colour (or temperature) and luminosity. There are only certain combinations of these properties that stars can have, which was discovered by Ejnar Hertzsprung and Henry Norris Russel in the early 20th century, and have given name to the diagram.

They noticed that a majority of the stars they observed end up on a diagonal sequence in the HR diagram, which they called the main sequence: the less massive, cooler and redder stars are found at the bottom, and the massive, hotter blues at the top (beware, the x-axis of the HR diagram is inverted!). To be quite frank, besides fusing hydrogen and trying to not collapse on itself (but that’s spoilers for what’s up ahead), the middle-aged main-sequence star doesn’t do much, and this is where most of the life of any star is being spent.

A sketch of the HR diagram, with the different stages of the Sun’s evolution marked. Note that the T Tauri phase is out of the scope of this blog post. Ga = billion years. Credit: Szczureq CC-BY-SA 4.0

Despite what the name “sequence” suggests, stars don’t move along it, as their temperature and luminosity don’t change much at this stage. How long does this phase last? The more massive the star, the shorter it lives. This is explained by the fact that the higher the mass of the star, the higher its temperature is; the higher temperature speeds up the process of fusing hydrogen into helium, and the star will deplete its fuel faster. As an example, the most massive stars of more than 100 solar masses burn through their fuel in a few million years, whereas the ones with only a small fraction of the solar mass will live for tens of billions of years. How massive can a star be? Astronomers have found a star weighing more than 300 times the Sun’s mass [eso1030], a very rare and exciting star!

Stars are born with different masses, which governs their temperature and their colour. We see this clearly in this group of young stars in the open star cluster NGC 3766 in the constellation of Centaurus (The Centaur). This image was taken with the MPG/ESO 2.2-metre telescope at La Silla [below]. Credit: ESO

The life crisis

The life crisis of a star of low (~0.3 solar masses) to intermediate mass (8 solar masses), the perhaps-getting-a-motorcycle phase, hits when the hydrogen in the core is depleted and the star reaches a new phase in its life: the beginning of the end. When there is no more fusion of hydrogen providing outwards pressure, the core starts to collapse. To maintain in equilibrium, the outer parts, the envelope as astronomers call it, swell into a red giant (red supergiant in the case of very massive stars, between about 8 and 30 solar masses) [eso1741], and the star enters the red giant branch, seen on the top right on the HR diagram.

Whilst the envelope is expanding and cooling, in the core the compression increases both the pressure and temperature. The core will continue to compress until it reaches high enough temperatures for helium fusion. Helium will fuse to carbon, which can pair up with more helium to form both nitrogen and oxygen, key ingredients for life as we know it here on Earth.

Using the PIONER instrument at ESO’s VLT, astronomers have directly observed patterns of convection cells on the surface of the huge red giant π1 Gruis. Each cell covers more than a quarter of the star’s diameter and measures about 120 million kilometres across. Credit: ESO

ESO Pionier instrument on the VLT interferometer.

Dust from red giants actually includes some of the elements produced in their interior, like carbon. In a paper [Astronomy & Astrophysics (below)] led by Julien Drevon of the Observatoire de la Côte d’Azur, France, astronomers used the MATISSE instrument on ESO’s VLT Interferometer [below] to study the red giant star R Sculptoris and imaged carbon-rich dust in the making. True proof of humans being stardust!

ESO CNRS VLT Matisse Multi-AperTure mid-Infrared SpectroScopic Experiment.

Red supergiants are also often enshrouded by dust. Betelgeuse, the red star in the Orion constellation, is one of the closest red supergiants, only around 600 light years from Earth.

Betelgeuse-a superluminous red giant star 650 light-years away in the infrared from the European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganisation](EU)Herschel Space Observatory (EU) Stars like Betelgeuse, end their lives as supernovae. Credit:Decin et al. Astronomy
& Astrophysics.

In late 2019, the star suddenly became much fainter. A team led by Miguel Montargès at KU Leuven, Belgium, used the SPHERE instrument at ESO’s Very Large Telescope (VLT) to explain that the dimming of Betelgeuse [eso2003] was caused by the star casting out dust.

The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL) SPHERE extreme adaptive optics system and coronagraphic facility on the VLT UT3, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level.

These images, taken with the SPHERE instrument at ESO’s VLT, show how the surface of the red supergiant Betelgeuse dimmed for several months. Credit: ESO/M. Montargès et al.

Post life-crisis

After the red giant branch and the initial life-crisis, the star has bought its motorcycle and is cruising down along the beach. But for the most massive stars, a bumpy ride awaits them.

When burning helium, the star moves from the red giant branch to the horizontal branch (named so because it is indeed horizontal in the HR diagram), and when burning carbon, it enters the second giant branch (which, due to historical reasons, is called the asymptotic giant branch). You might need to check the HR diagram above, because this can get confusing!

The names are of less importance, what matters is that the stars will move on the HR diagram, pulsating in brightness, with every new element it starts fusing. Because of this, the interior of stars ends up looking like an onion, with layers of progressively heavier elements the closer to the centre you get. But here the mass of the star is key again, since the more massive the star, the more massive the core, and the higher the capability to contract, meaning higher temperatures and –– yes, you guessed it –– fusion of heavier elements can take place!

Because of the difference in masses a clear distinction is made in how the stars’ lives eventually end.

The final stages

Stars don’t live forever. Stars with less than eight solar masses are not massive enough to fuse above oxygen (in rare cases up to neon and magnesium). Over time these stars leave their envelope, exposing the core: a white dwarf, supported by the pressure of tightly packed electrons. The remnant envelope can be lit up by the hot white dwarf, creating a planetary nebula [eso1532] (which has nothing to do with planets).

In this image of the Helix planetary nebula, taken by the Wide Field Imager (WFI), an astronomical camera attached to the MPG/ESO 2.2-metre telescope at the La Silla, we can see the ejected envelope being illuminated by the central white dwarf star, creating a stunning eye in the sky. Credit: ESO

Wide Field Imager on the 2.2 meter MPG/ESO telescope at Cerro LaSilla (CL)

Eventually the white dwarf will cool down, turning into a black dwarf.

The more massive stars will continue to create heavier and heavier elements in their core, compressing more and more and getting hotter and hotter. Until fusion reaches iron. Unlike fusion of lighter elements, which releases energy, fusing iron actually consumes energy. So once the core contains just iron, the outward pressure support of the star disappears, and it starts to collapse. For stars with masses around eight to 25 times the mass of the Sun, the intense gravity of the collapsing star crushes electrons and protons together to form neutrons, where the neutrons eventually will support the core, leaving behind an extremely dense neutron star.

Neutron Star L. Calçada/ European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU) (CL)

For the most massive stars [eso1034], the immense gravity will break the pressure of the neutrons and the core will collapse completely, forming a black hole. Paired with this collapse of material forming either a neutron star or a black hole, an explosion known as supernova often takes place. The conditions in these explosions are such that many elements heavier than iron can form.

The most massive stars will often end their lives in a supernova, just like the Crab Nebula (also known as Messier 1), here observed with the FORS2 instrument at the VLT.

The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL) FORS2 mounted on the VLT Telescope Unit 1 (Antu).

In the centre of the Crab Nebula, there is a neutron star, the remnant of the star that created the supernova.
Credit: ESO

However, we are not quite done yet. Remember the binaries from the beginning of this story? The ending lives of white dwarfs might not necessarily be too exciting. However, that doesn’t have to be the end: sometimes they too go out with a bang. If found in a binary with another star, the white dwarf can start stealing some of its companion’s material, causing the white dwarf to have a runaway fusion of material, resulting in a violent explosion that destroys the white dwarf in a supernova (or in the less violent cases, a micronova [eso2207]).

Additionally, if neutron stars are found in a binary with either a neutron star or a black hole, these can merge, creating some of the heaviest elements [eso1917], such as gold.

We are all stardust

Through stellar winds [eso0927], planetary nebula or supernova explosions, the newly created elements like carbon, oxygen, iron and gold are ejected into space, and will form new gas clouds. Eventually, those gas clouds will form new stars and the cycle begins again. This means that the next generation stars will have more of the heavier elements in them, and that stars carry a chemical fingerprint of their birth cloud, effectively acting as fossils of their birth environment.

Astronomers can measure these elements using spectroscopy, where the light from a star can be split up into its components, a spectrum, just like a rainbow. Every species of atoms leaves its own unique fingerprint in a star’s spectrum, which can be captured with instruments such as ESO’s FLAMES and X-Shooter, among many others.

European Southern Observatory(EU) FLAMES on The ESO Very Large Telescope, Cerro Paranal, Chile. FLAMES is the multi-object, intermediate and high resolution spectrograph of the VLT. Mounted at UT2, FLAMES can access targets over a field of view 25 arcmin in diameter. FLAMES feeds two different spectrograph covering the whole visual spectral range: GIRAFFE and UVES.

GIRAFFE on the VLT for intermediate and high resolution spectroscopy of galactic and extragalactic objects having a high spatial density used especially with FLAMES.

UVES spectrograph mounted on the VLT at the Nasmyth B focus of UT2.

ESO X-shooter on VLT on UT3 at Cerro Paranal, Chile.

The story of stars and their life is not only an astronomical story, but also the story of physics, chemistry and about us, and how we came to end up on a planet around a rather ordinary star in a galaxy called the Milky Way.

Note

[1] While brown dwarfs aren’t massive enough to fuse conventional hydrogen, they can fuse deuterium, an isotope of hydrogen that consists of a proton and a neutron instead of just a proton. This can last for several million years before the brown dwarf runs out of deuterium.

Science paper:
Astronomy & Astrophysics

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European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU) 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: Cerro 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”.

European Southern Observatory(EU) La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun).

ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE) 2.2 meter telescope at/European Southern Observatory(EU) Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) La Silla Observatory 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) , Very Large Telescope at Cerro Paranal in the Atacama Desert •ANTU (UT1; The Sun ) •KUEYEN (UT2; The Moon ) •MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). Elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

ESO Paranal Residencia

ESO Paranal Residencia inside near the swimming pool

ESO Paranal Residencia dining room

European Southern Observatory(EU)VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, •ANTU (UT1; The Sun ),•KUEYEN (UT2; The Moon ),•MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening.

ESO VLT Survey telescope.

ESO Very Large Telescope 4 lasers on Yepun (CL)

Glistening against the awesome backdrop of the night sky above ESO’s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system.

ESO New Technology Telescope at Cerro La Silla , Chile, at an altitude of 2400 metres.

Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

The Leiden Observatory [Sterrewacht Leiden](NL) MASCARA instrument cabinet at 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 telescopes, an array of twelve robotic 20-centimetre telescopes at Cerro Paranal,(CL) 2,635 metres (8,645 ft) above sea level.

ESO Speculoos telescopes four 1 meter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level.

TAROT telescope at Cerro LaSilla, 2,635 metres (8,645 ft) above sea level.

European Southern Observatory (EU) ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres.

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. A large project known as the Čerenkov Telescope Array composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile at, ESO Cerro Paranal site The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the. University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), The new Test-Bed Telescope 2 is housed inside the shiny white dome shown in this picture, at ESO’s LaSilla Facility in Chile. The telescope has now started operations and will assist its northern-hemisphere twin in protecting us from potentially hazardous, near-Earth objects.The domes of ESO’s 0.5 m and the Danish 0.5 m telescopes are visible in the background of this image.

Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) The open dome of The black telescope structure of the‘s Test-Bed Telescope 2 peers out of its open dome in front of the rolling desert landscape. The telescope is located at ESO’s La Silla Observatory, which sits at a 2400 metre altitude in the Chilean Atacama desert.

From ESOblog (EU): “Meet Eva Diaz – Head of Instrumentation at ESO’s Paranal Observatory”

From ESOblog (EU)

At

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

29 July 2022
People@ESO

Rebecca Forsberg
Rebecca is a science journalism intern at ESO. Prior to this position she has completed a bachelors and masters degree in astronomy & astrophysics, and is currently (when not working at ESO) doing a PhD at Lund Observatory, Sweden. Rebecca found her passion for writing and communicating science as a science reporter for the Swedish magazines Populär Astronomi and Lundagård.

ESO’s Paranal Observatory in Chile’s Atacama Desert is not only home to large telescopes, but also the many instruments attached to them, each with its own unique scientific purpose. We spoke to Eva Diaz, Head of Instrumentation at Paranal, about the importance of working as a team to solve never-before-encountered problems. Find out how she supports ESO in this blog post.

Eva Diaz

Eva Diaz likes the instruments she works with. These are not the instruments you would play music on, but rather the ones astronomers use to unravel the Universe’s secrets. Astronomical instruments are used to get as much data as possible from the incoming light collected by the telescopes: recording images, splitting light up in its components in a spectrograph, or even combining the light from many telescopes in an interferometer. Many such instruments exist at Paranal, with a plethora of different uses, and Eva leads a team of engineers that ensures these instruments work as they should. But where does this fascination for instruments come from?

Forging a new path

Let’s go back to the beginning. After finishing her undergraduate studies, Eva went to the Polytechnic University in Madrid, Spain, to study aeronautical engineering, and that’s where the path to scientific instrumentation was literally decided by chance: “I went with a friend, and they told us ‘we have one position at the military program and one at the scientific program, and you have to decide who is going to which’. So we tossed a coin, and I ended up in the scientific program,” she says, smiling at the memory, saying that she found herself very happy to be in the scientific environment.

She ended up working in instrument development at the Astrobiology Centre in Madrid. Instead of the ground-based telescopes used at ESO, the focus of her work in Spain was the development of instruments for space telescopes, like components for the European Space Agency’s INTEGRAL gamma-ray telescope, and the MIRI instrument on the James Webb Space Telescope. She even worked on Mars missions!

European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganisation](EU) Integral spacecraft.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) Webb MIRI schematic.

But as the years passed, she longed for a change of environment. “When I still had my children at home, I had no opportunity to work outside of Madrid. It was very difficult. So once they got older and started university, I searched for the opportunity to go outside.”

She saw the possibility of breaking new ground in another country, and picking up the position as Head of Instrumentation at ESO’s Paranal Observatory was a great opportunity to take her life into another direction. “I think it’s very difficult to reinvent yourself when you already have a set life. But I recommend it, it’s very good for you.” And so she did, seven years ago, and never looked back.

“I like to work in this type of environment a lot. I like the science, engineering, the desert and the people. It has been a big change and I’m very happy.”

Eva looking up at one of the unit telescopes of the VLT, standing on a platform going around the inside of the dome.
Credit: Gema Díaz. This image isn´t released under our CC-BY license.

The everyday life at the observatory

As the Head of Instrumentation, Eva leads a group of 15 people that works in two shifts. Normally she and her deputy make sure to overlap with both shifts, such that they can meet everyone in their group. “We work eight days up at Paranal, and then have six days free”. These free days Eva usually uses to enjoy life in the Chilean capital Santiago, where she lives, or to go traveling.

The everyday activity and schedule for the instrumentation group is strictly set, and is dictated by the Sun. Every morning they have a meeting where they review the night’s team report on what happened during the night, if there have been any issues, and things that need solving. It’s up to Eva to make sure that all problems are addressed, to communicate with the incoming astronomers about which possible issues to prioritize, and to help the team to run as smoothly as possible over the day, before they hand over operations to the night team again.

When we ask her about any particular proud moments she has had as Head of the Instrumentation group, she prides herself on the harmony between group members — each of whom has diverse abilities, knowledge and experience — and how they can come together to solve never-before encountered problems.

“It is a special group because we have different disciplines: cryogenics, mechanics, electronics, optics, a bit of everything,” she says.”This is the thing that I like the most: when we have a really difficult and challenging problem that is new or we don’t understand, we have to bring everyone together, sit down and come up with ideas on what to do, and you have to discuss this within the different disciplines. And this is really nice!”

Working as a team under pressure

There is nonetheless a specific moment that she remembers very strongly, during an observing run when a visiting astronomer was on site.[1] “The adaptive optics laser [below, which was important for the observations, had a problem and didn’t work. We decided to not run around, but to be calm and to do things very slowly, to understand what we were doing.”

The adaptive optics laser at ESO’s VLT [below] is key to get sharp images. The laser reaches 90 km into the sky, where it will excite sodium atoms, making them glow just like a star. With this new artificial star the turbulence of the atmosphere can be measured and corrected for by reshaping a thin mirror at millisecond speeds, a must for some observations, and a struggle if the system is not working.

With such complex systems it is not always the case that manuals cover all possible issues, and the instrumentation group sometimes have to solve problems ad hoc as they go. To fix the laser, the team had to dismount a whole piece of the mechanism. “We did it very slowly and carefully, with several people looking. And in the end, the laser did work! And this visitor was impressed with how we managed all of that, working slowly and coordinating within the team, doing all of the work in a safe way. I felt very, very good about that,” she says with pride.

The PARLA laser is used to generate an artificial star about 90 kilometres up in the atmosphere. By creating and observing such a bright point of light astronomers can probe the turbulence in the layers of the atmosphere above the telescope. This information is then used to adjust deformable mirrors in real time in order to correct most of the disturbances caused by the constant movement of atmosphere and create much sharper images. Credit: G.Hüdepohl (atacamaphoto.com)/ESO.

Driven by the challenge

The instruments are the bread and butter of any scientific research, and underpin all of the science done at ESO. Although, when it comes to the instruments at Paranal, there isn’t one in particular she likes more than the others. She cherishes the diversity and how they can suit different users and their needs. In Eva’s own words: “We have the four unit telescopes [of the VLT (below)] that are replicating a lot of hardware, but the instruments are all unique. So I think instrumentation is more interesting because we have more differences.”

Eva is not exaggerating, and the instruments at Paranal all have different expertise. Want to take spectra of many objects at once? Go for FLAMES.

European Southern Observatory(EU) FLAMES on The ESO Very Large Telescope, Cerro Paranal, Chile. FLAMES is the multi-object, intermediate and high resolution spectrograph of the VLT. Mounted at UT2, FLAMES can access targets over a field of view 25 arcmin in diameter. FLAMES feeds two different spectrograph covering the whole visual spectral range: GIRAFFE and UVES.

Do you instead want to study individual objects but with extremely detailed spectra? UVES and the upgraded CRIRES are your friends! Looking to catch some exoplanets? Look no further than SPHERE and ESPRESSO.

UVES spectrograph mounted on the VLT at the Nasmyth B focus of UT2.

CRyogenic high-resolution InfraRed Echelle Spectrograph. The original CRIRES was removed from UT1 in July 2014 for an upgrade and not offered from P94 onwards. CRIRES was installed on the UT3 Nasmyth B focus in Period 104. CRIRES will be offered for Period 107.

The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL) SPHERE extreme adaptive optics system and coronagraphic facility on the VLT UT3, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level.

ESPRESSO — the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations. ESPRESSO will use the light from any one, or all four, of the Unit Telescopes of the Very large Telescope to extend our capability to find planets around other stars and to measure the fundamental constants of physics.

ESO/ESPRESSO on the VLT installed at the incoherent combined Coudé facility of the VLT. It is an ultra-stable fibre-fed échelle high-resolution spectrograph (R~140,000, 190,000, or 70,000) which collects the light from either a single UT or the four UTs simultaneously via the so-called UT Coudé trains.

Even now, Eva and the team are preparing for the upcoming instruments 4MOST (4-metre Multi-Object Spectrograph Telescope) and MOONS (Multi-Object Optical and Near-infrared Spectrograph). These will allow astronomers to gather spectra of thousands of objects at once in the optical and infrared. Installing, operating and maintaining these two new advanced instruments will be a challenge for the team, but it’s a challenge they are prepared to tackle.

4MOST 4-metre Multi-Object Spectroscopic Telescope, on ESO’s VISTA, telescope, at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

ESO 4MOST instrument on the VISTA telescope annotated.

Depicton of ESO MOONS-a multi-objects spectrograph mounted at a Nasmyth focus at the VLT-Location Nasmyth focus at UT1, VLT

The Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument is a sophisticated planet hunter. It is capable of detecting and studying exoplanets orbiting nearby stars using a method known as high-contrast imaging. Here we see the complex optics and electronics of SPHERE, just before it was installed at the UT3 (Melipal) on the VLT and achieved successful first light in May 2014. Credit: ESO.

Even though Eva describes her work at ESO as mostly stable and set, there are unexpected things happening that can shake the steady routines at the observatory. These are often issues that one wouldn’t typically encounter as an instrument developer, and she can be faced with making challenging decisions.

For instance, sometimes there are earthquakes, or the risk of snow or ice covering the roads. “This is something that is new for me. When you are developing instruments and working in an office, you don’t care about the weather. But here you are always thinking about that and you see the astronomers in the evening going out and looking up to see if there are any clouds.”

But she never backs down from a challenge, and is driven by encountering new problems and working with her team to come up with the best solutions. For Eva, this is the thrill of the job, and why she is drawn to the scientific environment of ESO. “Astronomers are always looking for the most advanced technology, and I like that! Because it means that you’re always pushed forward and being challenged”, she says.

Having worked in instrumentation development in the past, she is now happy to keep contributing to this field from a new role and perspective.“I like even the small things that I can do for the team and for the observatory,” she says. “I might not revolutionise technology because I’m not working specifically with it. But maybe in the way I work, on a day-to-day basis, I can change some things.”

This is the Nasmyth platform of the UT2 (Kueyen) of the VLT. Here we see the installation of the high-resolution Ultraviolet and Visual Echelle Spectrograph (UVES) in the late 90’s. UVES is a multi-purpose instrument capable of handling a wide variety of astronomical objects, from the Solar System to the most distant Universe. Credit: ESO.

The power of diversity

When it is time for some well deserved rest and food down at the Residencia or, if it is not too cold, outside, Eva likes to walk down from the observatory through the desert. She explains that the tranquillity of the desert is almost like therapy. “You don’t have anything else but the blue sky and the brown ground.”

And after a day’s work of managing the instrumentation group and solving problems, she likes to read a book or enjoy a good series. “I also like to watch the sunsets, and I do like the clouds, which makes the sunsets more colourful and very wonderful.”

As a woman in instrumentation, Eva also talks about the necessity of having a clear goal and to continue to move steadily towards that, “It is very difficult, and sometimes I’ve gotten frustrated. But in the end, if you know where you want to go, and you are focused, the end result will be good.”

She really thinks diversity is key, independently of the field, and stresses the importance of, just like the instruments she works with, having people with different skills and abilities. “I think that we as women have a different way of thinking, we have our way of doing things. This is very useful in this type of work, and it helps with having a lot of success.”
Notes

[1] Most observations at Paranal are carried out in the so-called service mode, where ESO staff choose what programmes from the queue should be observed at any given time based on external conditions and scientific priority. But certain observations are performed in visitor mode, with the scientist(s) who requested the observations present at the observatory.

See the full article here .

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European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU) 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: Cerro 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”.

European Southern Observatory(EU) La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun).

ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE) 2.2 meter telescope at/European Southern Observatory(EU) Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) La Silla Observatory 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) , Very Large Telescope at Cerro Paranal in the Atacama Desert •ANTU (UT1; The Sun ) •KUEYEN (UT2; The Moon ) •MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). Elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

ESO Paranal Residencia

ESO Paranal Residencia inside near the swimming pool

ESO Paranal Residencia dining room

European Southern Observatory(EU)VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, •ANTU (UT1; The Sun ),•KUEYEN (UT2; The Moon ),•MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening.

ESO VLT Survey telescope.

ESO Very Large Telescope 4 lasers on Yepun (CL)

Glistening against the awesome backdrop of the night sky above ESO’s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system.

ESO New Technology Telescope at Cerro La Silla , Chile, at an altitude of 2400 metres.

Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

The Leiden Observatory [Sterrewacht Leiden](NL) MASCARA instrument cabinet at 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 telescopes, an array of twelve robotic 20-centimetre telescopes at Cerro Paranal,(CL) 2,635 metres (8,645 ft) above sea level.

ESO Speculoos telescopes four 1 meter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level.

TAROT telescope at Cerro LaSilla, 2,635 metres (8,645 ft) above sea level.

European Southern Observatory (EU) ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres.

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. A large project known as the Čerenkov Telescope Array composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile at, ESO Cerro Paranal site The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the. University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), The new Test-Bed Telescope 2 is housed inside the shiny white dome shown in this picture, at ESO’s LaSilla Facility in Chile. The telescope has now started operations and will assist its northern-hemisphere twin in protecting us from potentially hazardous, near-Earth objects.The domes of ESO’s 0.5 m and the Danish 0.5 m telescopes are visible in the background of this image.

Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) The open dome of The black telescope structure of the‘s Test-Bed Telescope 2 peers out of its open dome in front of the rolling desert landscape. The telescope is located at ESO’s La Silla Observatory, which sits at a 2400 metre altitude in the Chilean Atacama desert.

From ESOblog (EU): “What did you just say?”

From ESOblog (EU)

At

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

15 July 2022
Outreach@ESO

Anita Chandran
Anita Chandran is a science journalism intern at ESO. She recently completed her PhD in laser physics at Imperial College London, where she also worked with the science communication department on the ethics of artificial intelligence. She is a writer and editor, having co-founding Tamarind, a literary magazine focusing on the intersections between the arts and sciences.

Navigating astronomy’s confusing terminology.

Have you ever read the term ‘Earth-like’ exoplanet and thought ‘wow, I could move there!’? How about ‘no, it rains iron’. As a casual observer, some astronomical terms can be strange or misleading. In this ESO blog, we talk you through some of these terms so that you can navigate astronomical terminology like a true professional.

Stars

Early and late stars

Astronomers often refer to stars as ‘early’ or ‘late’ types. Early-type stars are generally hot and blue, whereas late-type ones are colder and red. While these names may suggest something about the star’s age, this is not the truth. This is actually an archaic remnant of a model of stellar evolution proposed in the 1800s that suggested early-type hot stars would gradually cool down and shrink to become late-type stars. This model was based on a physical process known as the Kelvin-Helmholtz mechanism, whereby objects radiate energy as they contract, which was thought to be the reason why stars shine. But if this was the case then the Sun could not have been shining for more than a few million years, whereas geological records showed that the Earth was several billions years old. Even though this idea was eventually abandoned, the early/late terminology has survived.

Stellar burning (as in “stars burn…”)

The last nail in the coffin for ‘early’ and ‘late’ type stars was the discovery that stars are fueled by nuclear fusion. In a star, light atoms such as hydrogen are forced together in the star’s core under tremendous temperature and pressure due to gravity. This causes them to fuse into heavier elements (in the case of hydrogen, into helium), releasing immense amounts of energy. This causes stars like our Sun to shine brightly (once the energy reaches the surface, which can take hundreds of thousands of years). Because fusion ‘fuels’ stars, astronomers often refer to this process as burning, so you might hear that a star is ‘burning hydrogen’. However, this shouldn’t be confused with ‘burning’ as used on Earth (the kind involving oxygen and a matchbox) as both processes are totally unrelated.

Planets

Astronomers are often at odds over how to define a planet in our Solar System. Many believe that planets are bodies massive enough to pull themselves together into hydrostatic equilibrium; this means that the gravity of the planet is enough to balance the outward pressure of the planetary material, so the planet ends up with a nearly spherical shape. But others impose additional requirements.

For instance, the definition by the International Astronomical Union (IAU) requires that, in addition to being in equilibrium and nearly round, planets must also orbit our Sun and have ‘cleared their neighborhood’, removing other astronomical bodies from their path. So technically, there are only eight planets, as Pluto does not fulfill the third criterion.

(In fact, the definition of planets has caused some consternation in the last few decades. If you, like the author of this blog post, were alive in 2006, you may recall the IAU’s choice to redefine the term ‘planet’. This may or may not, like the author of this blog post, have been a formative moment in your childhood, as Pluto was stripped of its planetary status. This could even, like the author of this blog post, have diminished your ability (aged 11) to remember the names of the planets, after the mnemonic you used was cruelly shortened to ‘My Very Easy Method Just Speeds Up Naming’.)

Credit: R. Munroe, https://xkcd.com/473/, CC-BY-NC 2.5.

What about exoplanets, which orbit stars other than the Sun? As per the IAU definition, exoplanets aren’t formally planets as they don’t revolve around our Sun. They have instead their own separate definition. Just like Solar System planets, they must be massive enough but not so massive to undergo nuclear fusion, which happens above 13 times the mass of Jupiter. Moreover, they can orbit objects that aren’t stars, like brown dwarfs or stellar corpses. But they must orbit something, which means that the so-called rogue planets aren’t strictly speaking planets

Other planet-based terminology that can also be misleading:

Habitable

You may believe that a ‘habitable’ exoplanet is one on which we could live. Not quite! Planetary habitability is a measure of how much potential a planet or moon has to develop and maintain environments that are hospitable to life. This often only implies that a planet has the possibility of having liquid water. But this definition is based on our sole example (so far) of life in the Universe: Earth. As we learn more about life, our definition of ‘habitable’ may have to be revised.

Habitable zone

Building on the idea of “habitable”, the habitable zone or “Goldilocks zone” is the range of orbits around a star at which the surface of a planet or moon can support liquid water, if there is sufficient pressure from the atmosphere. The latter bit is important: our Moon is obviously within the Sun’s habitable zone, but it can’t host liquid water because it lacks an atmosphere.

Earth-like (or Earth Analogue)

This term, as it suggests, usually refers to a planet or moon that is “like Earth”, or has environmentally similar conditions to those found on our home planet. The difficulty with this term arises when describing what “like Earth” is. Most of the time the only observable properties that we can measure in exoplanets are its mass and size. But think of Venus: it has pretty much the same size and mass as the Earth, but it’s a scorching hell covered with thick clouds of sulphuric acid. Definitely not like Earth! As a result, just because we refer to a planet as “Earth-like” doesn’t necessarily mean it’s all that much like Earth.

Planetary nebula

You might think this one was easy: planetary nebula, therefore, nebula involving planets! Unfortunately, you would be incorrect. The term planetary nebula refers to the expanding and glowing shell of gas that many stars shed in the later stages of their evolution. The name arose because many of these nebulae have round shapes that made them look like planets in the early days of telescope usage. Funnily enough, many planetary nebulae aren’t even round, and instead have symmetric shapes like an hourglass or a butterfly. But, as with many other terms in this list, the name has survived.

This extraordinary bubble, glowing like the ghost of a star in the haunting darkness of space, may appear supernatural and mysterious, but it is a familiar astronomical object: a planetary nebula, the remnants of a dying star. This is the best view of the little-known object ESO 378-1 yet obtained and was captured by ESO’s Very Large Telescope [below] in northern Chile. Credit: ESO.

This group portrait shows four bipolar planetary nebulae imaged using ESO telescopes. Studies of similar objects in the central bulge of the Milky Way have revealed an unexpected alignment. The objects shown here are much closer to Earth than those used in the new study, but demonstrate the varied forms of these spectacular objects.
The objects shown are: upper-left: the Dumbbell Nebula, Messier 27. upper-right: NGC 6302, lower-left: NGC 5189 and lower-right Fleming 1. Credit: ESO.

How we measure things

Light-year

We have to begin with a classic: the light-year. Like many units of measurement in astronomy, the confusion arises from the word “year”, which may suggest that it’s a unit of time. Instead, the light-year refers to the distance that light (or any electromagnetic radiation) can travel in a year in vacuum: about ​​9.46 trillion kilometres.

Arcminutes and arcseconds

Like the light-year, arcminutes and arcseconds may at first appear to be units of time but they are instead units to measure angles. If you think of there being 360 degrees in the full turn of a circle, an arcminute is 1/60th of a degree and an arcseconds is 1/60th of an arcminute. Astronomers often use these units to measure the apparent size of astronomical objects as seen from Earth; for instance, the Moon is about 30 arcminutes wide.

Parallax method via The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU).

The Parsec

Parsecs are so famously confusing that a whole franchise of Star Wars fans have argued about it since the 1970s, and that a whole film was dedicated to re-explaining it. So, what is a parsec? It’s a short form of “parallax second”, which again could make you think this is a unit of time when it is in fact a unit of distance. One parsec is the distance from which the separation between the Sun and the Earth would appear to be one arcsecond wide in the sky. It is approximately equal to 3.26 lightyears. This apparently convoluted way to define a unit of distance isn’t random, though. As the Earth moves around the Sun, nearby stars appear to move against the background of more distant stars. This apparent motion is called parallax, and it’s a powerful way to measure the distance to stars.

Honorable mentions

To round off, there are some final terms which may prove confusing to the astronomy enthusiast but which don’t fall into the above categories. So we list a couple of them here.

Metals

You are aware of a metal on Earth. Think of what a sword is made out of, or a can of soda, or even the keys to unlock your house. The shiny thing that conducts electricity and is sometimes magnetic. In astronomy, however, things are different. In space, where much of the matter is hydrogen and helium, the term “metals” is commonly used to describe any element that isn’t hydrogen or helium. Stars and other nebulae that have lots of heavy elements are usually referred to as “metal-rich” and the abundance of these heavy elements within a system is called “metallicity”. This is despite most of these elements –– like carbon, nitrogen or oxygen –– not obeying the regular definitions of metal that chemists and physicists use on Earth.

Early and Late-type Galaxies

Rather like early- and late-type stars, astronomers use “early” and “late” to refer to the structure of galaxies. Early-type galaxies tend to refer to elliptical galaxies, usually red and featureless, whereas late-type refer to spiral and irregular galaxies, bluer and with a richer structure. The nomenclature comes from Edwin Hubble who, in an early attempt to find some order within the plethora of shapes we see in galaxies, arranged them along a diagram now known as Hubble’s Tuning Fork. Fun fact: even though Edwin Hubble himself explicitly warned against using this to infer any sort of evolutionary trends, for quite some time astronomers thought that galaxies did evolve from left to right in this diagram. We now know that is not the case; if anything, when two spirals merge the resulting galaxy will often be an elliptical galaxy. But for the most part galaxies with different morphologies evolve in different ways.

Hubble’s tuning fork diagram, called like that due to its resemblance to the device used to tune musical instruments. Galaxies to the left are referred to as early-type galaxies, whereas those to the right are late-type ones. Despite this nomenclature, galaxies do not evolve from left to right in this diagram. Credit: Zoouniverse.

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European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU) 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: Cerro 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”.

European Southern Observatory(EU) La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun).

ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE) 2.2 meter telescope at/European Southern Observatory(EU) Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) La Silla Observatory 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) , Very Large Telescope at Cerro Paranal in the Atacama Desert •ANTU (UT1; The Sun ) •KUEYEN (UT2; The Moon ) •MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). Elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

European Southern Observatory(EU)VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, •ANTU (UT1; The Sun ),•KUEYEN (UT2; The Moon ),•MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening.

ESO VLT Survey telescope.

ESO Very Large Telescope 4 lasers on Yepun (CL)

Glistening against the awesome backdrop of the night sky above ESO’s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system.

ESO New Technology Telescope at Cerro La Silla , Chile, at an altitude of 2400 metres.

Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

The Leiden Observatory [Sterrewacht Leiden](NL) MASCARA instrument cabinet at 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 telescopes, an array of twelve robotic 20-centimetre telescopes at Cerro Paranal,(CL) 2,635 metres (8,645 ft) above sea level.

ESO Speculoos telescopes four 1 meter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level.

TAROT telescope at Cerro LaSilla, 2,635 metres (8,645 ft) above sea level.

European Southern Observatory (EU) ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres.

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. A large project known as the Čerenkov Telescope Array composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile at, ESO Cerro Paranal site The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the. University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), The new Test-Bed Telescope 2 is housed inside the shiny white dome shown in this picture, at ESO’s LaSilla Facility in Chile. The telescope has now started operations and will assist its northern-hemisphere twin in protecting us from potentially hazardous, near-Earth objects.The domes of ESO’s 0.5 m and the Danish 0.5 m telescopes are visible in the background of this image.

Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) The open dome of The black telescope structure of the‘s Test-Bed Telescope 2 peers out of its open dome in front of the rolling desert landscape. The telescope is located at ESO’s La Silla Observatory, which sits at a 2400 metre altitude in the Chilean Atacama desert.

From ESOblog (EU): “The quest for other worlds”

From ESOblog (EU)

At

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

24 June 2022
Science@ESO

Juliet Hannay
Juliet Hannay is part of the science communications team at ESO. She is a former student of the University of Glasgow acquiring a Bachelors and Masters degree in Astronomy and Physics. Juliet found a passion for science outreach and communication through her roles as Outreach Convenor, Vice President and President for the Women in STEM society and specialist editor for the Glasgow Insight into Science and Technology magazine.

Juan Carlos Muñoz Mateos
Juan Carlos Muñoz Mateos is Media Officer at ESO in Garching and editor of the ESO blog. He completed his PhD in astrophysics at Complutense University in Madrid (Spain). Previously he worked for several years at ESO in Chile, combining his research on galaxy evolution with duties at Paranal Observatory.

This spectacular image from the SPHERE instrument on ESO’s Very Large Telescope is the first clear image of a planet caught in the very act of formation around the dwarf star PDS 70. The planet stands clearly out, visible as a bright point to the right of the centre of the image, which is blacked out by the coronagraph mask used to block the blinding light of the central star. Credit: ESO/A. Müller et al.

The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL) SPHERE extreme adaptive optics system and coronagraphic facility on the VLT UT3, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level.

We humans have always pondered the question: “Are we alone in the Universe?”. A vital key in answering this philosophical question is discovering potential habitable worlds outside of our own Solar System. But how do we do this?

Exoplanets are planets beyond our Solar System that orbit stars other than the Sun. The first exoplanets were discovered back in 1992 by Aleksander Wolszczan and Dale Frail. Oddly enough, they didn’t orbit a normal star, like our Sun, but a pulsar –– a compact and rapidly rotating stellar corpse. In 1995 Michel Mayor and Didier Queloz found the first exoplanet around a Sun-like star, for which they were awarded the Physics Nobel Prize in 2019.

As of today there are more than 5000 confirmed exoplanets, a number that keeps rising steadily. Despite what this huge number may suggest, finding exoplanets is no walk in the park. This is because planets themselves emit very little or no light of their own. Instead, they reflect their parent stars’ light, which shines much more brightly in comparison. Seeing the light from a distant exoplanet is like spotting a dim candle in front of a raging forest fire. So, astronomers had their work cut out in their hunt for them!

In this article we’ll tell you about some of the methods astronomers use to detect and study exoplanets with modern astronomical facilities, including those at ESO’s observatories.

The radial velocity method

Radial velocity Image via SuperWasp.

Radial Velocity Method-Las Cumbres Observatory, a network of astronomical observatories, located at both northern and southern hemisphere sites distributed in longitude around the Earth.

LCO map 2017. Map of the Las Cumbres Observatory global network of robotic telescopes.

Las Cumbres Observatory site at the SAAO observing station at Sutherland, South Africa, altitude 1,450 metres (4,760 ft) above sea level.

The radial velocity method to detect exoplanet is based on the detection of variations in the velocity of the central star, due to the changing direction of the gravitational pull from an (unseen) exoplanet as it orbits the star. When the star moves towards us, its spectrum is blueshifted, while it is redshifted when it moves away from us. By regularly looking at the spectrum of a star – and so, measure its velocity – one can see if it moves periodically due to the influence of a companion.Credit: The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

Stars and their exoplanets are bound together by gravity. When a planet orbits a star, both of them are actually moving around their common centre of mass. This makes the star wobble back and forth, leading to small variations in the speed — or radial velocity — of the star, which betray the presence of a planet even if we can’t see it.

Astronomers can detect and measure these subtle changes in a star’s speed using spectroscopy, a technique that decomposes the light of an astronomical object into its constituent colours. A star’s spectrum contains dark lines due to certain chemical elements absorbing very specific colours. When a star moves towards us or away from us those lines shift to bluer or redder colours, respectively, due to something called the Doppler effect –– the same phenomenon that changes the pitch of a siren when a vehicle is approaching us or moving away. 51 Pegasi b, the planet that earned Mayor and Queloz their Nobel prize, was discovered this way.

However, planet detectives need to be extra vigilant with this method as the effect has a very small impact on the parent star. Even Jupiter, the largest planet in our Solar System, makes the Sun wobble by only 13 m/s during its orbit. So, as you can imagine, this minute effect can only be detected by very sensitive instruments.

One of such instruments is the High Accuracy Radial velocity Planet Searcher (HARPS) [below] attached to ESO’s 3.6-metre telescope at our La Silla Observatory in Chile. HARPS is so precise it can pick up tiny changes in a star’s speed of around 1 m/s or 3.5 km/h –– a gentle walking pace! At one point HARPS was responsible for two thirds of all the known exoplanets with masses less than that of Neptune. It also brought in the first planet around a star almost identical to the Sun, and thanks to the observations with this instrument, astronomers calculated that there are billions of rocky planets around red dwarfs in the Milky Way, the most abundant type of star in our galaxy.

HARPS also uncovered clear evidence of a planet orbiting Proxima Centauri, the closest star to Earth after the Sun, approximately four light-years away.

Centauris Alpha, Beta, Proxima, 27 February 2012. Skatebiker.

Proxima’s rocky world, a little more massive than Earth, has a temperature suitable for liquid water to exist on its surface, a major breakthrough in exoplanet research.

About 500 km north of La Silla we find ESO’s Paranal Observatory [below], which hosts another powerful planet hunter: ESPRESSO, the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations, mounted on ESO’s Very Large Telescope (VLT).

ESO/ESPRESSO on the VLT installed at the incoherent combined Coudé facility of the VLT. It is an ultra-stable fibre-fed échelle high-resolution spectrograph (R~140,000, 190,000, or 70,000) which collects the light from either a single UT or the four UTs simultaneously via the so-called UT Coudé trains.

ESPRESSO — the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations. ESPRESSO will use the light from any one, or all four, of the Unit Telescopes of the Very large Telescope to extend our capability to find planets around other stars and to measure the fundamental constants of physics.

In many ways ESPRESSO is the successor of HARPS: it’s extremely stable, and it can use any of the 8-m telescopes of the VLT, thus gathering more light and detecting even tinier stellar wobbles.

ESPRESSO recently discovered a second planet around Proxima Centauri; at just a quarter of Earth’s mass, this is one of the lightest exoplanets known. And it was also used to study an interesting planetary system around the star TOI-178, where planets orbit in harmonious resonance as illustrated in the video below.

Artist’s animation of the TOI-178 orbits and resonances (sound on!)
Artist’s impression of the planetary system around TOI-178. The orbital periods of the 5 outermost planets are in resonance, meaning that some planets align with each other every few orbits. In this animation, each planet has been assigned a different musical tone, creating harmonious chords when two or more planets are aligned. Credit: ESO/L. Calçada.

The transit method

When a planet passes between its parent star and us, it blocks a small fraction of the starlight from reaching us, creating a periodic dip in the brightness of the star which can be detected at Earth. This method is called transit photometry, and as of today it’s responsible for 75% of all known exoplanets, mostly thanks to NASA’s Kepler Space Telescope.

Planet transit. NASA/Ames.

NASA Kepler Space Telescope launched in 2009 and retired on October 30 2018.

The change in brightness is a very minute effect. So much so, that it can be comparable to small, unrelated changes in the star’s surface brightness itself such as starspots. Therefore, astronomers have had “false positive” detections of exoplanets and need to be careful before announcing their discovery.

Transits can also be timed to reveal the presence of additional planets. Say we already know a star has its own planet, which creates periodic dips in the brightness of the star. But when we carefully measure when these dips happen, we notice that sometimes they occur a bit earlier or later than predicted. This can be an indication of the presence of an extra planet, whose gravitational pull alters the motion of the first one. This is called “transit timing variation”, and it’s a powerful method to detect planets through their influence on their siblings.

Transit of an exoplanet (Europe to the Stars Clip)

Perhaps the best-known planetary system discovered via transits is TRAPPIST-1, a system of seven planets orbiting a cold dwarf star about 40 light-years away.

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The TRAPPIST-1 star and planet system; the ESO Belgian robotic Trappist National Telescope at Cerro La Silla, Chile.

The TRAPPIST-1 star, an ultracool dwarf, is orbited by seven Earth-size planets (NASA).

A size comparison of the planets of the TRAPPIST-1 system, lined up in order of increasing distance from their host star. The planetary surfaces are portrayed with an artist’s impression of their potential surface features, including water, ice, and atmospheres. Credit: NASA.

ESO Belgian robotic Trappist National Telescope at Cerro La Silla, Chile interior, altitude 2400 meters.

ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile, altitude 2400 meters.

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Some of them are at the right distance from the star to perhaps host liquid water. This system has both the largest number of Earth-sized planets found to date and the largest number of worlds that could support liquid water on their surfaces, a huge win for planet detectives.

The system takes its name from the TRAPPIST–South telescope, led by the University of Liège in Belgium in collaboration with the Geneva Observatory in Switzerland, and installed at ESO’s La Silla Observatory. Many other facilities have been used to study the transits in TRAPPIST-1, including NASA’s Spitzer Space Telescope, and ESO’s hawk-eyed High Acuity Wide-field K-band Imager (HAWK-I) instrument at the VLT.

National Aeronautics and Space AdministrationSpitzer Infrared Space Telescope no longer in service. Launched in 2003 and retired on 30 January 2020.

HAWK-I on the ESO Very Large Telescope at the Nasmyth A focus of Unit Telescope 4 (UT4) at the Paranal Observatory in Chile, with an elevation of 2,635 metres (8,645 ft) above sea level.

ESO’s Paranal and La Silla observatories are in fact home to several so-called “hosted telescopes” led by other institutions which are devoted to planetary transits. Besides the aforementioned TRAPPIST-South there’s the also Belgium-led SPECULOOS [below], the Next-Generation Transit Survey (NGTS) [below], MASCARA [below] and ExTrA [below]. These telescopes constantly scan the sky, looking for periodic dips in the brightness of thousands of stars.

Direct imaging

Even though the previous methods allow us to unambiguously detect exoplanets, they are indirect in that they rely on the effects that said planets exert on their host stars. But is it possible to actually take direct images of exoplanets? The answer is yes, but it’s extremely challenging.

Example of direct imaging-This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging. Credit: The National Aeronautics and Space Administration, The European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganisation](EU), and P. Kalas, The University of California-Berkeley and The SETI Institute.

Planets are buried under the glare of the stars they orbit; if you are observing from Earth, this image is made fuzzier by the turbulence in Earth’s atmosphere, which blurs the images of astronomical objects. To correct for the latter, astronomers use a technique called adaptive optics, whereby a small deformable mirror reshapes itself hundreds or even thousands of times per second to counteract the turbulence, monitoring a reference target in real time.

Using this technique, ESO’s NACO instrument at the VLT took the first ever picture of an exoplanet back in 2005, a ground-breaking feat for astronomy.

ESO/NACO on VLT Unit Telescope 1 (UT1).

The planet is about 5 times more massive than Jupiter and it orbits a brown dwarf, a small star with 13-14 times the mass of Jupiter.

This system was somewhat special in that it comprises a rather big planet orbiting a very small star, so their relative brightness are not dramatically different. But what happens when the parent star is millions or even billions of times brighter than the planet we want to image? In this case adaptive optics alone isn’t enough: besides correcting atmospheric turbulence we also need to somehow block the light of the star. Therefore, direct imaging instruments are usually equipped with devices called coronagraphs, which mask the light of the star, creating a sort of artificial eclipse inside the instrument.

NACO is now retired, but ESO still has one of the most advanced direct imaging instruments: SPHERE, the Spectro-Polarimetric High contrast imager for Exoplanet REsearch, mounted on the VLT. Since first beginning its pursuit of exoplanets in 2014, SPHERE has tracked a stunning time-lapse of an exoplanet orbit, took the first ever image of a multi-planet system around a Sun-like star, and even managed to image a newborn exoplanet for the first time.

What’s next?

Detecting exoplanets and their basic properties such as their mass or size already tells us a lot about them and how they formed. But astronomers are also interested in studying their atmospheres, and perhaps find biomarkers that could betray the presence of life.

One way to do so is to study transits at different wavelengths, analysing which colours of the star’s spectrum are absorbed or scattered by different chemicals in the planet’s atmosphere. An even more challenging approach is to directly take a spectrum of the planet itself.

While this is now mostly done on giant gas planets, astronomers want to eventually study the atmospheres of small rocky worlds like Earth, which requires much larger telescopes capable of detecting such faint sources. The hunt for exoplanets will thus benefit from future giant observatories, such as ESO’s 39-metre Extremely Large Telescope [below] currently under construction in Chile and set for first light by the end of the decade, which will allow astronomers to uncover the secrets of exoplanets with unprecedented detail.

See the full article here .

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European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte] (EU) 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: Cerro 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”.

European Southern Observatory(EU) La Silla HELIOS (HARPS Experiment for Light Integrated Over the Sun).

ESO 3.6m telescope & HARPS at Cerro LaSilla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE) 2.2 meter telescope at/European Southern Observatory(EU) Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) La Silla Observatory 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) , Very Large Telescope at Cerro Paranal in the Atacama Desert •ANTU (UT1; The Sun ) •KUEYEN (UT2; The Moon ) •MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). Elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

European Southern Observatory(EU)VLTI Interferometer image, Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level, •ANTU (UT1; The Sun ),•KUEYEN (UT2; The Moon ),•MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening.

ESO VLT Survey telescope.

ESO Very Large Telescope 4 lasers on Yepun (CL)

Glistening against the awesome backdrop of the night sky above ESO’s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system.

ESO New Technology Telescope at Cerro La Silla , Chile, at an altitude of 2400 metres.

Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light, with an elevation of 2,635 metres (8,645 ft) above sea level.

European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

European Southern Observatory(EU) ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

European Southern Observatory(EU)/MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

The Leiden Observatory [Sterrewacht Leiden](NL) MASCARA instrument cabinet at 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 telescopes, an array of twelve robotic 20-centimetre telescopes at Cerro Paranal,(CL) 2,635 metres (8,645 ft) above sea level.

ESO Speculoos telescopes four 1 meter robotic telescopes at ESO Paranal Observatory 2635 metres 8645 ft above sea level.

TAROT telescope at Cerro LaSilla, 2,635 metres (8,645 ft) above sea level.

European Southern Observatory (EU) ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres.

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. A large project known as the Čerenkov Telescope Array composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile at, ESO Cerro Paranal site The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the. University of Wisconsin–Madison and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), The new Test-Bed Telescope 2 is housed inside the shiny white dome shown in this picture, at ESO’s LaSilla Facility in Chile. The telescope has now started operations and will assist its northern-hemisphere twin in protecting us from potentially hazardous, near-Earth objects.The domes of ESO’s 0.5 m and the Danish 0.5 m telescopes are visible in the background of this image.

Part of the world-wide effort to scan and identify near-Earth objects, the European Space Agency’s Test-Bed Telescope 2 (TBT2), a technology demonstrator hosted at ESO’s La Silla Observatory in Chile, has now started operating. Working alongside its northern-hemisphere partner telescope, TBT2 will keep a close eye on the sky for asteroids that could pose a risk to Earth, testing hardware and software for a future telescope network.

European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) The open dome of The black telescope structure of the‘s Test-Bed Telescope 2 peers out of its open dome in front of the rolling desert landscape. The telescope is located at ESO’s La Silla Observatory, which sits at a 2400 metre altitude in the Chilean Atacama desert.

From ESOblog (EU): “It takes a village…”

From ESOblog (EU)

At

The European Southern Observatory [La Observatorio Europeo Austral] [Observatoire européen austral][Europäische Südsternwarte](EU)(CL)

10 June 2022
On the Ground

Juan Carlos Muñoz Mateos.
Juan Carlos Muñoz Mateos is Media Officer at ESO in Garching and editor of the ESO blog. He completed his PhD in astrophysics at Complutense University in Madrid (Spain). Previously he worked for several years at ESO in Chile, combining his research on galaxy evolution with duties at Paranal Observatory.

Paranal Observatory pictured with Cerro Paranal in the background. The mountain is home to one of the most advanced ground-based telescopes in the world, the VLT. The VLT telescope consists of four unit telescopes with mirrors measuring 8.2 meters in diameter and work together with four smaller auxiliary telescopes to make interferometric observations. Each of the 8.2m diameter Unit Telescopes can also be used individually. With one such telescope, images of celestial objects as faint as magnitude 30 can be obtained in a one-hour exposure. This corresponds to seeing objects that are four billion (four thousand million) times fainter than what can be seen with the unaided eye.

When browsing through the captivating images of the cosmos that we routinely publish you may have asked yourself ‘how did they take this image?’ The answer is… complicated. In this blog post we’ll tell you how these pictures come to be and the role of everyone that makes them possible.

This comparison shows a new view of the Helix Nebula acquired with the VISTA telescope[below] in infrared light (left) and the more familiar view in visible light from the MPG/ESO 2.2-metre telescope [below] (right). The infrared vision of VISTA reveals strands of cold nebular gas that are mostly obscured in visible light images of the Helix. Credit: ESO/VISTA/J. Emerson. Acknowledgment: Cambridge Astronomical Survey Unit.

It all begins with an idea

Astronomers don’t just randomly point telescopes at the sky-they always want to answer specific questions. How do stars form in galaxies? What’s the composition of the atmospheres of exoplanets? What’s the mass of the black hole at the center of our galaxy? They then think about what observations are needed to answer those questions and identify which observatories have the telescopes and instruments required to obtain that data.

Everyone wants to get a chance to observe their favorite astronomical targets, but the amount of observing time available at any given telescope is always limited. Astronomers therefore have to compete for observing time with their peers.

They do so by writing proposals where they detail their scientific problem and how they plan to tackle it. These proposals are evaluated by a panel of experts based on different criteria: how scientifically relevant is the question the team wants to answer? Can their proposed observations actually address this question? Are they using the right telescope and instrument for the job?

Organizing all this requires a considerable amount of work. At ESO this is led by the so-called Observing Programme Office but many other people are involved. For instance, ESO astronomers at the User Support Department help their peers with any questions they may have while preparing their proposals.

From idea to reality

The lucky few whose proposals get accepted need to prepare the observations. You can think of them as recipes with a sequence of steps: point the telescope to the target, configure the instrument in the desired way, gather data for some time… Astronomical instruments are highly sophisticated and it can take years of experience to master them. To make it as easy as possible for everyone to use them, ESO provides a dedicated online tool that simplifies the process. Users only need to specify the sequence of steps, and trained ESO staff will execute them at the telescope. It’s like having professional chefs cooking your favorite recipes on demand! The User Support Department once again assists astronomers when preparing their observations.

Most of the time astronomers don’t even have to travel to the observatories. Instead, their requested observations are stored in a database, and ESO staff on site will decide on the fly what to observe at any given time. This depends on multiple factors, like the scientific priority of the observations, how urgent they are, or the ambient conditions –– not all projects require perfect weather or a moonless sky, for instance.

The Paranal Control Room at night, when the action takes