From ESOblog: “From the ground to the sky”

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From ESOblog

27 March 2020. People@ESO.

As well as being an Operations Astronomer at the ESO ALMA Regional Centre, María Díaz Trigo is a world-renowned expert in high-energy astrophysics and lends her expertise to X-ray space missions. In this week’s blog post, we find out what Maria does on a daily basis, how she fits everything in, and why she thinks it’s important that ground- and space-based astronomy evolve in parallel.

María Díaz Trigo

Artist”s impression of the black holes studied by the astronomers, using ULTRACAM attached to ESO’s Very Large Telescope [below]. The systems — designated Swift J1753.5-0127 and GX 339-4 — each contain a black hole and a normal star separated by a few million kilometres. That’s less than 10 percent of the distance between Mercury and our Sun. Because the two objects are so close to each other, a stream of matter spills from the normal star toward the black hole and forms a disc of hot gas around it. As matter collides in this so-called accretion disc, it heats up to millions of degrees. Near the black hole, intense magnetic fields in the disc accelerate some of this hot gas into tight jets that flow in opposite directions away from the black hole. The orbital period of Swift J1753.5-0127 — just 3.2 hours — is the fastest found for a black hole. The orbital period of GX 339-4, by contrast, is about 1.7 days. Credit: ESO/L. Calçada.

Q. Firstly, could you tell us a bit about your role at ESO? What do you do on a daily basis?

A. I’m an ALMA astronomer, meaning half of my time is dedicated to ALMA Observatory duties.

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

This spans a range of activities, including scheduling different projects to happen at the right time, under the right conditions.

The other half of my time is spent on my own research, where I am really free to work on whatever I want. So I focus on X-ray binary systems, which consist of either a small black hole (by which I mean around ten times the mass of the Sun!) or a neutron star, as well as a normal star. The black hole or neutron star pulls matter from the normal star. This process, called accretion, powers the most energetic phenomena in the Universe and releases a lot of X-rays. These X-rays can be observed using dedicated space telescopes, and I look at these X-ray observations together with observations of the same systems in other wavelengths of light made by telescopes on the ground. This gives me a lot of information about what’s going on in different parts of the system.

Q. What first got you interested in astronomy?

A. At university I specialised in particle physics, but after my master’s degree, particle physics seemed to be at the stage where the most exciting science had already been done. It is also difficult to work on your own research in particle physics; everything needs big expensive particle accelerators and extensive collaborations. So I switched to astronomy because of the amazing number of things that can be done with telescopes — both by collecting new data and by analysing data that already exist.

This artist’s impression shows the surroundings of a supermassive black hole, typical of that found at the heart of many galaxies. The black hole itself is surrounded by a brilliant accretion disc of very hot, infalling material and, further out, a dusty torus. There are also often high-speed jets of material ejected at the black hole’s poles that can extend huge distances into space. Observations with ALMA have detected a very strong magnetic field close to the black hole at the base of the jets and this is probably involved in jet production and collimation. Credit: ESO/L. Calçada.

Q. And you are now an expert in high-energy astrophysics. Could you tell us a bit more about your research and why it inspires you?

A. When a black hole or neutron star in a binary system pulls matter from a companion star, a disc forms around the black hole or neutron star, consisting of matter dragged off of the companion star, and this is what feeds the heavier object. At some point this disc is heated so much that the upper layers evaporate and matter flies away from the system in the form of winds. These winds have speeds of the order of 1000 km/s and are detected predominantly in X-rays and sometimes with telescopes that observe optical light. However, these winds are “slow” compared to the very narrow, collimated, extremely high-speed jets that are also expelled from the system and detected from radio to infrared wavelengths.

I study these winds and jets and try to figure out how they fit in with the rest of the system. One of the biggest mysteries is how to feed black holes so that they get as big as those found at the centres of galaxies, which weigh as much as millions of Suns. Even if black holes are attracting matter from gas and stars, it seems as if a significant part of that matter is ejected in winds and possibly jets before it even gets to the black hole, so we’re still wondering how matter actually reaches the black hole so it can grow.

Q. How does this research fit in with being a European Participating Scientist for JAXA’s X-ray Imaging and Spectroscopy Mission (XRISM)? Why did you choose to take on this role?

Artist’s impression of the JAXA/NASA X-ray Imaging and Spectroscopy Mission (XRISM).
Credit: JAXA

A. Well, I wanted to contribute to making the mission a success in getting us to the next stage of X-ray instrumentation! XRISM is a JAXA/NASA collaborative mission, with participation from the European Space Agency (ESA). It will carry a revolutionary micro-calorimeter providing a spectral resolution higher than conventional X-ray imaging spectrometers by a factor of 30. A micro-calorimeter will also be flown on ESA’s next large X-ray space mission Athena and we hope to learn lots of lessons from XRISM!

I was selected by ESA around two years ago to represent the European scientific community on XRISM, and I mostly contribute scientific expertise in the area of X-ray binaries. I meet with a whole group of participating scientists every six months in person and monthly remotely, and we form part of the mission’s science team. We are currently considering which X-ray-emitting objects we should observe during the first six months after XRISM is launched in 2022, which will be the performance verification phase. During this period we will use the telescope to observe lots of different sources to check how the instrument fares — where it works well and where it works less well — so that the science community can prepare their own observations for the operational phase.

Q. Do you think it’s important that ground-based astronomy and space-based astronomy evolve in parallel, with astronomers from both areas working together? If so, why?

A. Absolutely! Astronomy is a complex science and one telescope observing one wavelength of light is not enough to have a full picture of what’s going on out there in the Universe. For example, one mystery surrounding black holes is that the supermassive black holes at the centre of galaxies emit X-rays, and so do the little black holes that I observe in binary systems, but medium-sized black holes don’t emit any X-rays! We didn’t even know whether these medium-sized black holes existed until gravitational waves allowed us to detect them for the first time. Now we can find out more about them and figure out why we don’t see any X-rays from them.

Q. And what about collaboration between different scientific organisations? Why is this important?

A. Knowledge sharing is always important. ESO and ESA have an ongoing collaboration to share knowledge and experience in the areas of science, technology and operations. This is mostly done through a working group for each of the three areas. I am part of the science working group in which we try to see where we can collaborate to advance scientific projects. For example, for some ESA space missions to achieve their full science goals, their observations are followed up by ESO’s ground-based telescopes.

ALMA itself is a partnership between ESO, the US National Science Foundation, and Japan’s National Institute of Natural Sciences in cooperation with the Republic of Chile. So representatives from most continents are involved and the telescope is showing what can be achieved through a global collaboration. It’s hard work but very, very rewarding.

Space missions are also becoming more complex and expensive, making it difficult for one agency alone to build and fund them. Costs and expertise have to be shared; this is demonstrated in XRISM where expertise comes from scientists around the world.

Q. It sounds like you’ve got a lot on your plate! How do you fit everything in?

A. (María laughs) I do what I can! It is a lot, but it’s one of the challenges that comes with working in science. The 50% of time many scientists have available to spend on “‘science” is not really all “own research time” in the end. We have to do a lot of work for the community otherwise the community can’t move forward. Being involved in advisory committees or selecting proposals from other scientists for observations with a given telescope indeed leaves less time for research, but it means that we extend and share our expertise.

For example, for XRISM I contribute my knowledge about X-ray binaries, but there are so many other objects out there that emit X-rays. I’ve recently been learning from cosmological experts who work on very, very distant X-ray-emitting clusters of galaxies.

Q. Finally, you’ve also got a degree in philosophy. How does that fit in with your interests in physics and understanding the Universe?

A. Aside from being influenced by a fantastic teacher, I was always very attracted by philosophy because it’s at the core of thinking. Centuries ago, philosophers were the physicists of their times – their aim was to understand the Universe. Nowadays unfortunately we’re locked into small areas of expertise making it difficult to see the bigger picture. I found this very unsatisfactory; I can do many things to better understand my little black holes but in the end our aim is to discover why we are here and where we go now. I can’t answer these questions with my data alone.

Seeing the bigger picture gives us a direction, something to aim for. Fortunately, we are now moving in the direction of multidisciplinary work; people from different areas are working together and combining their knowledge to solve bigger problems.

See the full article here .


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

ESO VLT 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,

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

ESO VLT 4 lasers on Yepun

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

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

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

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

ESO/E-ELT,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).

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

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. a large project known as the Cherenkov Telescope Array, composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile. 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