The mission of Spectrum-Roentgen-Gamma (SRG) is a collaborative project of Russians and Germans. Their mutual aim was to make an X-ray map of the universe. On 21 June 2019, the mission launched into space to create this first of its kind map.
Of course, in the past other space telescopes were working with high-tech X-rays and showing a good view of distant space objects. But the SRG is the first one to make a complete map of the universe using high-tech X-rays.
This map allows scientists to observe the expansion of the universe and its acceleration. The plan was to cover the whole sky for half a year.
SRG’s Scientific Goal
SRG’s scientific goal was related to cosmology – it was to create a three-dimensional map which to show how the universe expands controlled by the dark energy. Specialized scientists examined the repulsive force of the so-called dark energy through clusters of galaxies. The way the galactic clusters distribute themselves affects the structure and history of the universe.
SRG created a map of around 1 00 000 galactic clusters. They did this by detecting the X-ray brightness coming from the intergalactic plasma. SRG’s other target was to identify approximately three million supermassive black holes, as well as X-rays from 700 000 stars in the Milky Way.
Russia is Back in the Game
It is not a secret that the recent decades, Russia’s astrophysics community has suffered because of financial reasons. So this mission gave them a chance to resurrect. Since the whole project is a collaboration between Russia and Germany, SRG carried two X-ray telescope instruments:
- The first one called eRosita – a German-built one;
- The other one called ART-XC – a Russian-built one – ART-XC was an unprecedented instrument of its kind for Russia;
So now Russia is proud to be back in the world of science.
The lit-off of the spacecraft happened on a Russian-built M-rocket. In the past, there had been other X-ray sky surveys as well, but they hadn’t been that successful. One of them was a German mission called ROSAT, but it was sensitive only to soft X-rays. NASA’s Chandra X-ray Observatory and NuStar are similar missions, but they can only observe small parts of the sky.
SRG’s two instruments cover X-rays that stretch to higher energies. Each one of the devices consists of seven X-ray telescopes. They frame the same part of the sky simultaneously. Since they work in combination, they provide many more photons than a single telescope.
Since the photons in space are just a few, scattered at a considerable distance from each other, SRG’s two instruments can define the amount of energy contained in each photon.
The Future of SRG
SRG’s mission is supposed to be in action for four years, during which time its two instruments will be able to map the sky eight times. This fact will allow researchers to compare the maps and examine them for any changes.