This is how the energetic universe looks like through eROSITA X-ray telescope

Our deepest view of the X-ray sky.

The eROSITA telescope onboard SRG has recently captured a stunning view of the entire sky- revealing the nature of the hot universe. The view is about four times deeper than the previous all-sky survey by the ROSAT telescope 30 years ago and has yielded around ten times more sources: nearly as many as have been discovered by all past X-ray telescopes combined. 

Over 182 days, the eROSITA X-ray telescope onboard SRG has completed its first full sweep of the sky. This new map of the hot, energetic universe contains more than one million objects, roughly doubling the number of known X-ray sources discovered over the 60-year history of X-ray astronomy.

Peter Predehl, the Principal Investigator of eROSITA at the Max Planck Institute for Extraterrestrial Physics (MPE), said, “This all-sky image completely changes the way we look at the energetic universe. We see such a wealth of detail – the beauty of the images is stunning.”

Annotated version of the eROSITA First All-Sky image. Several prominent X-ray features are marked, ranging from distant galaxy clusters (Coma, Virgo, Fornax, Perseus) to extended sources such as Supernova Remnants (SNRs) and Nebulae to bright point Annotated version of the eROSITA First All-Sky image. Several prominent X-ray features are marked, ranging from distant galaxy clusters (Coma, Virgo, Fornax, Perseus) to extended sources such as Supernova Remnants (SNRs) and Nebulae to bright point sources, e.g. Sco X-1, the first extrasolar X-ray source to be detected. The Vela SNR is to the right of this image, the Large Magellanic Cloud in the bottom right quadrant, the Shapley supercluster in the upper right (though not easily visible in this projection).Jeremy Sanders, Hermann Brunner, Andrea Merloni and the eSASS team (MPE); Eugene Churazov, Marat Gilfanov (on behalf of IKI)

Looking outside the body of our Galaxy, the more significant part of the eROSITA sources are active galactic nuclei, accumulating supermassive black holes at cosmological distances, interspersed with a cluster of galaxies, which show up as extended X-ray haloes shining because of the hot gas confined by their immense concentrations of dark matter. 

The all-sky image uncovers in exquisite detail the structure of the hot gas in the Milky Way itself, and the circum-galactic medium, which surrounds it, whose properties are critical to understanding the development history of our Galaxy. The eROSITA X-ray map likewise uncovers stars with strong, magnetically active hot coronae, X-ray binary stars containing neutron stars, black holes or white dwarves, and spectacular supernova remnants in our own and other nearby galaxies, for example, the Magellanic clouds.

Due to its size and close distance to Earth, the “Vela supernova remnant” which is shown in this picture is one of the most prominent objects in the X-ray sky. The Vela supernova exploded about 12000 years ago at a distance of 800 light-years and overlaps with at least two other supernova remnants, Vela Junior (in the picture seen as bluish ring at the bottom left) and Puppis-A (top right). Vela Junior was discovered just 20 years ago, although this object is so close to Earth that remains of this explosion were found in polar ice cores. All three supernova explosions produced both the X-ray-bright supernova remnants and neutron stars, which shine as intense X-ray point sources near the centres of the remnants. The quality of the new eROSITA data of this “stellar cemetery” will give astronomers many exciting new insights into the physical processes operating in the hot supernova plasma as well as for exploring the exotic neutron stars.Peter Predehl, Werner Becker (MPE), Davide Mella

Mara Salvato, the scientist at MPE who leads the effort to combine eROSITA observations with other telescopes across the electromagnetic spectrum, said, “We were all eagerly awaiting the first all-sky map from eROSITA. Large sky areas have already been covered at many other wavelengths, and now we have the X-ray data to match. We need these other surveys to identify the X-ray sources and understand their nature.”

The Shapley supercluster of galaxies is one of the most massive concentrations of galaxies in the local universe at a distance of about 650 million light-years (z~0.05). Each of the dozen extended structures is itself a cluster of galaxies, consisting of 100s to 1000s of individual galaxies, each denoting an intersection of filaments making up the large-scale structure in the Universe. This image spans 16 degrees across the sky (about 30 times the size of the full moon), which translates into about 180 million light-years across at the distance of the Shapley supercluster. The images on the left show a zoom of the the most massive clusters in the Shapley supercluster.Esra Bulbul, Jeremy Sanders (MPE)

“The survey is also a treasure trove of rare and exotic phenomena, including numerous types of transients and variables, such as flares from compact objects, merging neutron stars, and stars being swallowed by black holes. eROSITA often sees unexpected bursts of X-rays from the sky. We need to alert ground-based telescopes immediately to understand what’s producing them.”

Assembling of the image was indeed a colossal task, and why not, scientists had received and processed almost 165 GB of data collected by eROSITA’s seven cameras.

Miriam Ramos-Ceja, a member of the eROSITA operations team at MPE, said, “We used to usually check and monitor the health of the instrument daily, in cooperation with our colleagues in Moscow who operate the SRG spacecraft. This means we can respond quickly to any anomalies.”

The pale blue dot at the center of the ring is the X-ray binary MAXI J1348-630, which went into outburst in February 2019. On the top left, the red source is the star beta Centauri, one of the brightest stars in the southern sky.Credit: Georg Lamer (Leibniz-Institut für Astrophysik Potsdam), Davide Mella

“We’ve been able to react to these immediately to keep the instrument safe while collecting data at ~97% efficiency. It’s amazing to be able to communicate in real-time with an instrument located 1.5 million kilometers away!”

“Data downlink occurs daily. We perform immediate quality checks on the data before it is being processed and analyzed by the teams in Germany and Russia.”

For now, scientists are busy analyzing this first all-sky map. They hope that the images and catalogs are probably helpful in the understanding of cosmology and high-energy astrophysical processes.”

Rashid Sunyaev, the Lead Scientist of the Russian SRG team, said, “Overall, during the next 3.5 years, we plan to get seven maps similar to the one seen in this beautiful image. Their combined sensitivity will be a factor of 5 better and will be used by astrophysicists and cosmologists for decades.”