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The eROSITA X-ray sky in 360°

May 17, 2021

By now, the SRG/eROSITA telescope has complete more than half of its third scan of the entire X-ray sky. The first all-sky image was released in summer 2020, which can be seen here in an interactive 360° view. This map contains more than one million objects, most of them active galactic nuclei at cosmological distances, marking the growth of gigantic black holes over cosmic time. Clusters of galaxies in the new map will be used to track the growth of cosmic structures and constrain cosmological parameters. Closer to home, stars with hot coronae, binaries and supernova remnants dot our Galaxy - the hot band in the middle of the image.

With increasing exposure (each point in the sky has been observed by the SRG/eROSITA telescope for more than 500 seconds), the sensitivity of the survey increases, and it becomes possible to plot the energy spectra of individual sources and study their variability over time. The map below is projected from the position of the telescope at the Lagrange point L2. So put yourself in the location of eROSITA and enjoy a unique view of the X-ray sky!

You can easily enlarge areas of interest in the viewer. Travel along the plane of the Galaxy (along the equator in this image), observing the zone of strong absorption of X-rays by cold atomic and molecular gases. Or focus on the numerous bright galactic and extra-galactic X-ray sources above and below the galactic plane.

The good angular resolution (~ 30 arcseconds) and the high sensitivity of eROSITA made it possible to already map more than a million compact sources and tens of thousands of extended ones. Only the brightest of them are visible on the map as dots. The resolution of the map does not allow you to distinguish the rest of the objects individually; they merge, adding to the brightness of the diffuse radiation of the Galaxy and to the radiation of the extragalactic X-ray background.

The colours in this map where chosen to represent different energies of the incoming X-ray photons: Red corresponds to photons with energies of 0.3–0.6 keV, green to 0.6–1 keV, and blue to 1–2.3 keV. This – more or less – corresponds to a characteristic temperature of the radiating source: 3-6 million degrees (red), 6-10 million degrees (green), and 10-25 million degrees (blue).

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