Garching (dpa) – On the trail of big bang forces with X-rays: Germany’s eRosita telescope is designed to give researchers an illuminating new look at the dark energy of the universe. Ultimately, eRosita is supposed to provide a sky map that shows the universe and its evolution in unprecedented quality.
June 21 A Russian rocket would launch the telescope into the Spectrum-RG space observatory from the Baikonur spaceport. Researchers speak of the largest Russian-German bilateral space project.
Hopes are high. “I don’t mean to say we’re going to solve the mystery of this dark energy, but at least we’re on the trail,” says Peter Predehl, scientific director of eRosita at the Max Planck Institute for Alien Physics in Garching near Munich . “The telescope has enormous potential.”
ERosita (Extended Roentgen Survey with an Imaging Telescope Array), built under the direction of the Garching Institute with the participation of other facilities in Germany and Russia, aims to make visible the development of space and its structures by rays X. Because light from distant galaxies travels for a long time, the telescope can go back up to six billion years. “We can look back and we can see: what the universe was like then, what it looks like today,” says Predehl.
The key lies in galaxy clusters, collections of thousands of individual galaxies linked together by gravity. “The galaxy clusters form a large-scale structure that looks like a cosmic lattice,” explains Predehl. The distribution of galaxy clusters shows how the universe has expanded since the Big Bang. This is largely determined by dark energy, which remains invisible. For eRosita, the forces can be measured by the gas in galaxy clusters that is 100 million degrees hot: the temperature is so high that the gas emits X-rays which eRosita picks up.
“The hotter objects, the more energy they glow,” says Thomas Mernik, project manager at the German Aerospace Center (DLR), which has signed contracts with Russian space organization Roscosmos and funded eRosita with MPI. The telescope will not primarily observe clusters of individual galaxies. “We are completely digitizing the entire sky and will be able to create a sky map based on that data,” says Mernik. The dynamics of galaxy clusters allow conclusions to be drawn about the dynamics of the universe as a whole. “It will help us better understand the nature of dark energy.”
ERosita should identify around 100,000 galaxy clusters within four years and determine their distribution in the universe. To do this, eRosita draws on research from the German Rosat satellite, which provided spatial data for eight years and sank in the Indian Ocean in 2011. Among other things, Rosat had found more than 150,000 new sources of cosmic x-rays. Thanks to the new technology, eRosita is twenty times more sensitive than Rosat. Seven systems of mirrors form the optics. At the center of each mirror system is a highly sensitive camera, specially developed for the mission.
American researchers founded X-ray astronomy in 1948 when they discovered X-rays from the sun as a captured German V2 rocket was flying high. X-rays outside the atmosphere were previously unknown. Because the earth’s atmosphere blocks the rays. Observatories such as Spektrum-RG, which in addition to eRosita, the Russian AR telescopeT-XC are therefore stationed on satellites. ART-XC and eRosita measure in different energy zones and will partially interact when observing clusters of galaxies.
After starting Baikonur, the researchers will first test the instruments. After three months, eRosita will reach the target area about 1.5 million kilometers from Earth. “The first results can be expected at the beginning of September”, says Predehl.
Even eRosita won’t be able to directly show dark energy and dark matter, which together make up 95% of the universe, but only the effect of their powers. Most of the universe remains a mystery. Predehl: “Dark here means: we don’t know.”