Here is what it looks like the whole sky through the eyes of the X-ray


A space telescope launched in July 2019, has just completed its first survey. For months, the telescope eROSITA on-board the space observatory Spektr-RG has traversed the entire sky, collecting observations for the survey the deepest of the sky in the wavelengths of x-rays.Now, all these data have been compiled in a map containing more than a million bright objects X-ray – doubling the approximate number of these objects of the past 60 years of astronomy in x-rays.

“This image the whole sky completely changes the way we see the universe of energy,” said astrophysicist Peter Predehl, the principal investigator of eROSITA at the Max Planck Institute for Extraterrestrial Physics (MPE).

“We see such a wealth of detail – the beauty of the images is really breathtaking. ”

Most astronomical objects emit X-rays, but in different proportions compared to the other wavelengths. X-rays have wavelengths are very short and are, therefore, very-high-energy – emitted by the hottest objects and most energy, such as black holes, neutron stars, galaxies quasars and the remnants of a supernova.

The rest of the supernova Vela. (Peter Predehl, Werner Becker / MPE, Davide Mella)

X-rays are invisible to the naked eye, such as radio waves. Thus, the sky X-ray looks very different from what we see when we look up at night. In addition, and in contrast to radio waves, X-rays are mostly blocked by the earth’s atmosphere, so the only way to study them is to send telescopes into space.

A number of telescopes to X-rays have been made, but the most recent survey in X-rays in the sky was made decades ago, from 1990 to 1999, the satellite ROSAT. The new map of the sky collected by the eROSITA joint Russian-German is, according to the team, four times deeper than the map from the data ROSAT.

It has been a painstaking work. The space observatory Spektr-RG is located in one of the points lagrangian of the Earth, a pocket of stable gravity created by the interaction between the Earth and the Sun, about 1.5 million kilometers.

The instrument has collected 182 days of data, each exposure between 150 and 200 seconds, for a total of 165 gigabytes. Every day, the team connects the satellite to download what he had collected. Then, all these raw data had to be processed and collected.

The Supercluster Shapley galaxies. (Esra Bulbul, Jeremy Sanders / MPE)

“We all waited with impatience the first card in the all-sky eROSITA,” said the astrophysicist Mara Salvato of MPE. “Large areas of the sky have already been covered in many other wavelengths, and we now have the X-ray data to make them match. We need these other surveys to identify X-ray sources and understand their nature. ”

Most of the sources on the card – about 77 percent – are supermassive black holes accrétant active material in the nuclei of galaxies, or what we call active galactic nuclei. These objects are extremely energetic, and there are many out there.

There are also clusters of galaxies, radiate X-rays due to hot gas forced by their gravity collective; they represent about 2 percent of the objects.

Other objects are a lot closer to home. In the Milky Way, the stars with crowns hot magnetically active constitute 20% of the objects. The remaining percent is made up of an assortment of binary X-ray bright remnants of supernova, and flares, such as those emitted by a star torn apart by black holes.

transient x-rays(Georg Lamer / Leibniz-Institut fur Astrophysik Potsdam, Davide Mella)

The map also reveals the structure of hot gas in the milky Way galaxy and the gas that surrounds it. It is a mine of data on the point of reveal a lot of information on the universe of x-rays And this is only the beginning. Over the next few years, the observatory will perform seven other surveys, which will combine for an overall map of the sky much more sensitive.

“With a million sources in just six months, eROSITA has already revolutionized the astronomy of the X-ray, but this is only a taste of what will happen. This combination of the area of the sky and the depth is transformative, ” said the astrophysicist, Kirpal Nandra of MPE.

“We sample already a volume cosmological of the Universe hot-much bigger than what was previously possible. Over the next few years, we will be able to probe even further, where the first cosmic structures giant, supermassive black holes were formed. . ”

We can’t wait.


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