ROSCOSMOS & DLR - Spetrum-RG orbital X-ray observatory patch.
Jan. 13, 2021
By mid-December 2020, the Russian orbital X-ray observatory Spectrum-RG completed the second sky survey. The addition of these two surveys makes it possible to almost double the sensitivity of the X-ray maps received by the observatory's telescopes.
Image above: RGB-map of the sky, built by the SRG / EROSITA telescope based on the sum of the first two sky surveys (c) Gilfanov, Medvedev, Sunyaev and the Russian consortium eROSITA, 2021.
“According to the eROSITA telescope, we see about a million sources that are located on the hemisphere for which Russian scientists are responsible for processing the data. Of these, about 200,000 are stars located in our Galaxy, active in the X-ray range. " - says Corresponding Member of the Russian Academy of Sciences Marat Gilfanov, employee of the Space Research Institute of the Russian Academy of Sciences.
“This is a colossal amount of data that is first encountered by X-ray astronomers. The sky appears amazing and "alive", we see that in six months between two scans of the sky many tens of thousands of X-ray sources have changed their brightness. Every day, exploring a large circle in the sky just one degree wide, we discover the variability of hundreds of sources that were dimmer or, on the contrary, bright just six months ago, "says academician Rashid Sunyaev, scientific director of the Russian Spectrum-RG observatory.
About 20% of all sources discovered by the eROSITA telescope are stars in our Galaxy, with very hot corona like the sun, but much brighter. Accordingly, X-ray flares on these stars are much brighter than on the Sun. The eROSITA data also contain a wealth of information on instabilities in accretion disks around supermassive black holes, which regulate the flow of accreting matter to them. eROSITA detects blazars in which relativistic jets emit - jets of matter ejected from the vicinity of supermassive black holes at speeds close to the speed of light.
Spectrum-RG & eROSITA orbital X-ray observatory
The astrometric satellite Gaia operates in the same halo orbit around the L2 point "not far" from the Spektr-RG observatory. The observatory is equipped with a specialized optical telescope and monitors the proper motion of more than a billion stars in our Galaxy. Relatively recently, the scientific group of the Gaia telescope published new catalogs of stars and changes in their position, obtained from the results of a five-year scan of the Galaxy. All objects in our Galaxy have been registered that are bright enough in the optical range of the spectrum and have changed their position in the sky by one or two milliseconds of an arc during this time.
At the same time, extragalactic objects - quasars and active galactic nuclei are located at much greater distances from us and therefore remain stationary for observers from Earth in the celestial sphere. Comparison of the catalog of X-ray sources "Spectrum-RG" with the catalog of Gaia objects, as well as with the results of measurements of their proper motions, makes it possible to distinguish between extragalactic sources and stars in our Galaxy, whose corona is bright in X-rays. The fact that the energy flux of their optical and infrared radiation is much higher than in the X-ray range also helps to distinguish stars. For most quasars and active galactic nuclei, this ratio is much smaller.
“We are working on catalogs of X-ray sources so that all astronomers working in other ranges of the spectrum can immediately check how an object of interest behaves in X-rays,” continues Academician Sunyaev.
“The data obtained allowed us to increase the contrast of the multicolor X-ray sky map that the eROSITA telescope continues to accumulate. A number of structures found on the map of the first survey, for example, the southern bubble eROSITA (in galactic coordinates), are seen more clearly, and now they can be examined in detail, ”says Marat Gilfanov.
Image above: RGB map of the sky area covered during the first three weeks of scanning, which began in mid-December 2020, by the SRG / eROSITA telescope (c) 2021 Gilfanov, Medvedev, Sunyaev and the Russian consortium eROSITA.
Recall that the "eROSITA bubbles" are gigantic structures tens of thousands of light years across, that is, comparable to the diameter of the Galaxy. The sky map obtained by the eROSITA telescope after the first survey of the sky and, in particular, the detection of the southern bubble, proved that their appearance is associated with activity in the center of our Galaxy tens of millions of years ago.
Three weeks ago, the Russian observatory Spectrum-RG began the third survey of the sky (out of eight planned). Scanned for the third time already more than 5000 square degrees in the celestial sphere. The eROSITA telescope, manufactured by the Max Planck Institute for Extraterrestrial Physics in Germany, continues to accumulate X-ray photons, discover new sources of X-ray radiation and monitor changes in their brightness. The enterprises of the State Corporation "Roscosmos" control the satellite, antennas for long-distance space communications receive scientific data every day and send commands to the satellite and scientific instruments located at a distance of one and a half million kilometers from the Earth (four times farther than the Moon). Scientists from IKI RAS are processing scientific data on powerful computers in the project data center.
Related article & links:
Milky Way on x-ray sky map
https://orbiterchspacenews.blogspot.com/2020/06/milky-way-on-x-ray-sky-map.html
ROSCOSMOS Press Release: https://www.roscosmos.ru/29814/
Spectrum-RG: http://roscosmos.ru/srg/
Images, Text, Credits: ROSCOSMOS/Orbiter.ch Aerospace/Roland Berga.
Best regards, Orbiter.ch
