Stars and galaxies in apparent nothingness

Observational data from the European Southern Observatory provide a deeper view into space

The picture shows one of the fields, which is about the size of the full moon. With the naked eye there is nothing to see at this point in the sky. The bright yellow star at the top of the picture is about eight times too weak for it, although it is the brightest object on the picture. For eight hours, this image was exposed with a large telescope, so that a total of over 50, 000 objects can be seen. © AIfA of the University of Bonn
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Valuable new insights into the starry sky have now been obtained by astronomers through the analysis of observation data from the European Southern Observatory in Chile. Staff members of the Argelander Institute for Astronomy at the University of Bonn have won 63 pictures, including, for the first time, showing extremely distant and correspondingly faint galaxies from the childhood of the universe.

If you observe the night sky from a dark place, you can easily recognize the band of the Milky Way, which can be resolved into stars with a small telescope. For the glimpse seemingly less interesting are the star-poor regions of the sky. Only hours of observations with large telescopes reveal even in these so-called "empty fields" a large number of weak objects. "While we look at the Milky Way in our mother galaxy and thus in our cosmic neighborhood, observations of empty fields allow us to penetrate to very distant places in our universe, " explains Bonn astronomer Professor Dr. med. Peter Schneider.

This will allow scientists to gain insight into the early stages of our universe: the light from these regions has been on the road for billions of years before it hit the telescope, revealing the image of how the distant galaxies looked in their "childhood" - that is one of the reasons why science is interested in such observation data.

Extreme data processed

In the recently completed "ESO Deep Public Survey" program, astronomers thus observed three such apparently "empty fields" with the 2.2-meter telescope of the European Southern Observatory

(ESO) in La Silla, Chile. All three fields, whose area in the sky is four times as large as the full moon, were viewed with different color filters. So the researchers wanted to collect color information about the distant objects. The sheer size of the sky area observed, the use of five different filters and the extremely high exposure time (more than a hundred hours per field) resulted in a gigantic amount of data: About one and a half terabytes of raw data - that's about as many as 2, 000 CD-ROMs - Can no longer be handled with conventional workstations, especially since this amount of data temporarily multiplied during processing. display

"We have therefore installed a special parallel computer for this processing - also called data reduction -, " says Professor Schneider. In a long-standing project, the scientists also had to develop the necessary software at the same time, since there was nothing comparable on the market. Very few groups worldwide are able to reduce data of this kind at all.

Young galaxies with irregular shapes

After more than a year of arithmetic work, the researchers were now able to provide 63 finished images of the worldwide community of astronomers. In addition to galactic stars as well as nearby elliptical and spiral galaxies, the pictures also show extremely distant and correspondingly faint-colored objects. "Using special color selection methods, for example, we can select objects that are so far away that the light has traveled over 80% of the time since the Big Bang, " explains Hendrik Hildebrandt, Ph.D. student at Argelander. Institute of Astronomy (AIfA). "Such a selection is also badly needed, as some of the images on a surface as large as the full moon show more than 50, 000 galaxies."

In these objects you can see galaxies, as they looked at the time of their childhood. Instead of the regular, symmetrical forms known from the nearby universe of spiral galaxies or elliptical galaxies, irregulatory systems dominate in those early days, forming many new stars. Hendrik Hildebrandt has now found several thousand of these so-called "Lyman-break galaxies" together with other AIfA employees. One of the most amazing features of these young galaxies is that they are "clumping together" under the influence of their own gravity, just as galaxies are today, even though they had far less time for this process. This clumping can be measured with the help of the Bonn data with previously impossible to reach precision.

(University of Bonn, 21.04.2006 - NPO)