March 1, 2024

Scientists reveal what the sky looks like in X-ray vision: ScienceAlert

There’s an old trope in science fiction about someone who suddenly gets x-ray vision and looks through solid objects. It turns out that this is a physical impossibility with our Mark I eyes. However, astronomers have found a way around this challenge that allows us to study the Universe with X-ray vision.

It’s called X-ray astronomy and it’s been around for 60 years. It reveals some of the most energetic and violent events and objects in the cosmos. These include things like bright quasars, supernova explosions, flows of hot gas between galaxies, and hot young stars.

Recently, astronomers from the eROSITA consortium at the Max Planck Institute for Extraterrestrial Physics announced the latest X-ray dataset from the eROSITA survey. It covers half of the X-ray sky and reveals information about 900,000 distinct X-ray sources.

That’s more than anything ever detected in the decades-long history of X-ray astronomy, including discoveries made with Chandra and other orbiting observatories.

This image shows half the sky in X-rays, projected in a circle with the center of the Milky Way on the left and the galactic plane running horizontally. Photons were color-coded according to their energy (red for energies 0.3-0.6 keV, green for 0.6-1 keV, blue for 1-2.3 keV). (MPE, J. Sanders/eROSITA consortium)


eROSITA is a soft X-ray imaging telescope aboard the Spectrum-RG satellite. Its first all-sky survey, called eRASS1, took place over 7 months starting on December 12, 2019.

At its most sensitive setting, the telescope detected 170 million X-ray photons. This allowed cameras to measure their energies and arrival times.

The astronomy team, led by principal investigator Andrea Merloni, created a first data catalog. They have also published more than 50 new scientific articles based on their discoveries.

After finishing this first survey, the instrument performed three more all-sky scans between June 2020 and February 2022. This enormous trove of X-ray data will be released soon. The video below explains more about the mission.

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eROSITA’s Treasury of X-ray Sources

X-ray astronomy focuses on hot, energetic objects and events in the Universe. These would be the cores of galaxies (where supermassive black holes hide), supernova explosions, newborn stars and other places where matter is heated to high temperatures.

This preliminary eRASS1 dataset identifies about 710,000 supermassive black holes, 180,000 X-ray-emitting stars in the Milky Way, and 12,000 galaxy clusters. It also covers a small number of other exotic sources, such as X-ray-emitting binary stars, supernova remnants, pulsars, and other objects.

“These are mind-blowing numbers for X-ray astronomy,” says Andrea Merloni, eROSITA principal investigator and first author of the eROSITA catalog paper. “We detected more sources in 6 months than the large flagship missions XMM-Newton and Chandra did in almost 25 years of operation.”

The first release of eROSITA data is a rich, “multilayered” view of the sky at various X-ray energies. Each energy level tells astronomers something about the objects and events that emit the X-rays. And for each set of images and data, the consortium provides more information.

There are lists of source classes, sky positions, energies and precise photon arrival times at the instrument.

“We have made a huge effort to release high-quality data and software,” added Miriam Ramos-Ceja, who leads the eROSITA Operations team. “We hope this will broaden the base of scientists around the world working with high-energy data and help expand the frontiers of X-ray astronomy.”

cutouts showing details in X-ray views of Earth's sky
X-ray image of eROSITA with the newly discovered filament between two galaxy clusters. The distribution of galaxies (white outlines, top left), as seen in the Two Micron All Sky Survey, follows the filament structure. In the SLOW simulation, which is adapted to reproduce the main features of the Local Universe, this individual system with both clusters and the spine of the filament is also reproduced. (Dietl et al. 2024)

Focusing on specific x-ray objects

eROSITA’s scientific goals are to use X-rays as a way to detect the hot intergalactic medium of 50 to 100,000 clusters and groups of galaxies. It also analyzes the hot gas in the filaments between them. These filaments glow in X-rays.

The instrument is also tasked with detecting accumulated black holes hidden in galaxies. Finally, he studied the physics of galactic X-ray sources (which include pre-main sequence stars, supernova remnants, and X-ray binaries).

At least one of the articles published with the new research data uses X-ray data to constrain cosmological models using galaxy clusters. In a published image, we see a filament of newly discovered material.

It stretches between a part of the galaxy cluster Abell 3667 and the nearby cluster Abell 3651. This could help astronomers determine how much matter there is in the so-called “hot-hot intergalactic medium.” It gives insight into the formation of large-scale structures (such as galaxy clusters) in the Universe.

The nearby Virgo galaxy cluster also appears in the eRASS1 survey and provides a way to study large-scale filamentary structures. In particular, astronomers want to understand the physical effects operating on the outskirts of these enormous galaxy clusters.

Using the new survey data, as well as other all-sky images, a scientific team explored the structure of the cluster’s periphery. This included high-energy emissions around galaxies and groups within the cluster. They also studied a so-called “X-ray extension” 320 kiloparsecs long near the M49 galaxy.

Crop showing details of the Virgo cluster in X-rays
This X-ray image shows the entire extent of the Virgo Cluster in X-rays as seen by eROSITA. The bright white spot in the center is the central galaxy M87. The hazy white glow around M87 is the very hot gas between the galaxies. It extends further in some directions than others and is not circular. This is evidence that the Virgo Cluster is still in the process of formation. (McCall al. 2024)

Past and future work of eROSITA

eROSITA has enabled a huge leap forward in X-ray astronomy since its launch in June 2019. It began operating in October of that year, providing high-resolution X-ray views of the cosmos. While scanning the sky, glimpsed changes in a distant quasar called SMSS J114447.77-430859.3.

These changes give some clues about the growth of the black hole at the heart of the quasar. He observed changes in brightness variations at the heart of the quasar, indicating that the black hole swallows part of the material that is lost at its event horizon. Other materials escape in the form of strong winds.

The instrument also detected a newly formed black hole in the early Universe and traced the existence of hot gas around our galaxy, the Milky Way. The instrument had its first light on October 22, 2019. It is currently in safe mode and technicians are evaluating its health status.

This article was originally published by Universe Today. Read the original article.

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