The Universe at all Scales

The birth and life cycle of galaxies, stars and planets – these are the main interests of the astrophysicists at the University of Vienna. Their research also contributes to understand the important issue: Under what conditions does life exist in the universe?

Feb. 1, 2016

The Milky Way arches above the Paranal platform, home of ESO’s Very Large Telescope, allowing astronomers to study distant galaxies and the birth of stars.


Copyright: ESO/H.H. Heyer

“Even with the largest telescopes available today, the first galaxies of the universe are visible to us as Vienna’s city centre would be from the moon,” says astrophysicist Bodo Ziegler. So it is fascinating that astronomers can still learn a lot about these early galaxies. Bodo Ziegler, Head of the Research Group Extragalactic Astrophysics, and his colleague Helmut Dannerbauer, for example, have been able to completely record how stars are formed in a galaxy cluster ten billion light years away. They observed the surroundings of the enormous “Spiderweb Galaxy” MRC 1138-262 with the APEX telescope (Atacama Pathfinder Experiment) of the European Southern Observatory (ESO). “The interstellar gas clouds where stars are born absorb light. However, radio telescopes like APEX allow us to observe the cold universe so that we can also survey these cold gas clouds,” Ziegler explains. In their study, the astrophysicists found that the creation of stars is not only usually obscured by dust clouds but also occurs in unexpected places. They discovered the secret blueprints of a galactic metropolis.

To increase our understanding of the evolution of galaxies, we must study galaxies from different cosmological eras."

Bodo Ziegler, Professor of Galaxy Formation in the Early Universe

The first galaxies were formed as early as 500 million years after the Big Bang. In the 13 billion years since then, they have changed their shape and composition repeatedly, but also new galaxies were formed. “In order to advance our understanding of the universe, we must look at its entire development – from our Milky Way all the way back to the first galaxies,” says Ziegler. It is not only about how stars are formed, he explains, but about all physical aspects of the evolution of galaxies. In order to study these, “we have to examine galaxies with many different approaches in all wavelength ranges – X-rays, visible light, infrared radiation and radio waves. We call this the multiwavelength approach.”

The researchers predominantly use spectroscopic methods to determine the physical properties of galaxies. Bodo Ziegler’s team participated in the international project CALIFA (Calar Alto Legacy Integral Field Area) that observed more than 600 very different galaxies in our Galactic neighbourhood at the Calar Alto observatory in southern Spain over three years using a special 3-D spectroscopic method. This new method allowed them to distinguish on spatially resolved scales the physical properties, such as their kinematic characteristics, their chemical composition and their stellar populations more precisely than ever before. In another project, Ziegler and his team observe galaxies that are between 5 and 8 billion light years away. The focus is on potential interactions between galaxies clustered closely together. For their analysis, they combine spectroscopy using the largest telescopes of ESO (of which Austria is a member) stationed in Chile’s Atacama Desert and high-quality imaging from the Hubble Space Telescope.

How stars were born

How do diffuse interstellar gas clouds form, evolve and eventually collapse to form stars and planets? This is the key research question of João Alves and his Research Group Star and Planet Formation. “You could say we make sonograms of pregnant clouds. We develop different methods to study these star-bearing wombs,” says the astrophysicist. To see through the interstellar gas clouds, Alves and his Research Group primarily use infrared telescopes such as Herschel and ESO’s Very Large Telescope.

Diffuse interstellar gas clouds become stars, which host earth-like planets and burn out or explode, creating a multitude of elements that eventually end up in other stars, planets and our blood.”

João Alves, Professor of Stellar Astrophysics

One of the Group’s key research areas is the 3-D visualisation of data from space. Their 3-D analyses recently uncovered an optical illusion that had not been detected with the previous 2-D analyses: The Gould Belt in the Milky Way is not actually a ring of stars but a projection effect. This puts the existence of the “belt” of stars near our Sun, which was first identified in the 19th century, into question. As part of the international project, the researchers also created the first 3-D map of the regions around our Sun. Their 3-D analysis also revealed the presence of enormous streams of young stars, traced by the massive but short-lived O- and B-stars. The data came from the European Space Agency (ESA) satellite Hipparcos.

Alves’ Group is also involved in the Gaia satellite project of ESA and is eager to explore Gaia data with the new 3-D techniques developed for the Hipparcos satellite. “The data will allow us to reconstruct the regions near our Sun in a never before seen resolution and create accurate maps of stars and the interstellar gas between them. We will be able not only to reconstruct our Galactic neighbourhood accurately but, by doing that, understand the origins of sun-like stars and the build-up of galaxies like our Milky Way,” says João Alves. The first data will be published for analysis in the late summer of 2016. In the near future, Alves wants to focus more on one of humankind’s big questions: Are we alone in the universe? “We have learned in the last few years that one in five stars has an earth-like planet with water. This gives the question new relevance,” Alves explains.

Conditions for habitable planets

The question why life is possible on Earth and not on some other planets is the focus of Manuel Güdel and his Research Group Star and Planet Formation. Co-operating with researchers from other groups and departments, Güdel is studying the astrophysical factors that make planets habitable.

The current faces of Venus, Mars and Earth can tell us how the young solar system might have looked. Through them, we can understand our origins.”

Manuel Güdel, Professor of Astronomy, Satellite and Experimental Astronomy

He heads a national research network, for which the Austrian Science Fund (FWF) recently extended funding until 2020. How do the properties of stars influence planets? Under what conditions do some proto-atmospheres survive on planets, and why do some evaporate? What properties must a planet have to create suitable conditions for life and, in particular, liquid water? And how do all these factors have to interact to finally result in a habitable planet? “Our goal is to gain a comprehensive view of the different factors and their interactions using modelling by 2020,” Güdel explains. His team is initially focusing on our solar system – particularly Earth with its neighbours Mars and Venus – as a field of study. In the case of Earth, its mass, insolation and the astronomical architecture of our solar system made life possible. However, the Group is also studying extrasolar planetary systems with very different properties.

In another project, Güdel’s Group is studying the properties of so-called protoplanetary disks – enormous disks of gas and dust that can later form planets. “It is important to understand protoplanetary disks in order to understand where planets come from, how they form, grow and create their first atmosphere,” the astrophysicist explains. The project is funded by the EU, the FWF and the Austrian Research Promotion Agency (FFG).

At the same time, Güdel’s Group and other researchers at the Department of Astrophysics are involved in a number of space missions. Franz Kerschbaum’s team is, for example, developing research technology, e.g. on-board software for satellites. Because of their activities, Güdel’s and Kerschbaum’s teams are involved in the planned ESA exoplanetary missions PLATO, CHEOPS and ARIEL, the ESA planetary mission SMILE, the James Webb telescope (NASA and ESA) and the ESA X-ray telescope Athena, as well as the future evaluation of the gathered data.

Instruments for ESO’s Extremely Large Telescope

Austrian scientists are also involved in the development of three instruments for the European Extremely Large Telescope (E-ELT), which is currently under construction. The enormous ESO telescope with its 39-metre diameter primary mirror will be the world’s largest telescope for the visible and near-infrared range. Led by the Viennese astrophysicists, the Austrian team is involved in the development of the camera MICADO (Multi-AO Imaging Camera for Deep Observations), which will permit more precise imaging of near-infrared wavelengths. The Mid-Infrared ELT Imager and Spectrograph (METIS) will provide high-resolution data from the mid-infrared spectrum. The third instrument, MOSAIC, will allow spectroscopic analyses of very distant galaxies. One of the tasks of the Austrian team is to develop components for the data reduction software of the instruments.

Department for Astrophysics