February 26, 2024

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

There is an old story from science fiction about someone who suddenly gains x-ray vision and can see through solid objects. It turns out to be a physical impossibility with our Mark I eyeballs. However, astronomers have found a way around this challenge, allowing 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. This includes 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 released the latest trove of X-ray data from the eROSITA survey. It covers half of the X-ray sky and reveals information about 900,000 different X-ray sources.

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

This image shows half of the X-ray sky projected onto a circle with the center of the Milky Way on the left and the galactic plane horizontal. Photons are 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 telescope on board the Spectrum-RG satellite. The 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 the cameras to measure their energy and arrival times.

The astronomy team, led by lead researcher Andrea Merloni, has compiled an initial catalog of data. They also published more than 50 new scientific articles based on their findings.

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

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eROSITA’s treasure trove of X-ray sources

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

This preliminary data set from eRASS1 identifies approximately 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 binaries, supernova remnants, pulsars and other objects.

“These are stunning numbers for X-ray astronomy,” says Andrea Merloni, eROSITA principal investigator and first author of the eROSITA catalog article. “We discovered more resources in six months than the major flagship missions XMM-Newton and Chandra discovered in their nearly 25 years of operation.”

The first data release from eROSITA is a rich, “multilayered” look at the sky at different 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, celestial positions, energies and precise arrival times of the photons on the instrument.

“We have put a tremendous amount of effort into releasing high-quality data and software,” said 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 push the boundaries of X-ray astronomy.”

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

Zoom in on specific X-ray objects

The scientific objectives of eROSITA are to use X-rays as a way to detect the hot intergalactic medium of 50 to 100,000 clusters and groups of galaxies. Hot gas in the filaments between them is also examined. Those filaments glow in X-rays.

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

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

It extends between part of the star cluster Abell 3667 and the nearby cluster Abell 3651. This can help astronomers determine how much matter is in the so-called “warm-hot intergalactic medium.” It provides insight into the formation of large-scale structures (such as clusters of galaxies) in the universe.

The nearby Virgo Cluster of galaxies also features in the eRASS1 survey, providing a way to study large-scale filamentary structures. In particular, astronomers want to understand the physical effects that occur in the outskirts of these massive galaxy clusters.

Using the new survey data and other images of the entire sky, a scientific team examined the structure of the cluster’s outskirts. That included the high-energy emissions around galaxies and groups within the cluster. They also studied a so-called 320 kiloparsec long “X-ray expansion” near the galaxy M49.

Cutaway showing details of Virgo Cluster on X-rays
This X-ray shows the full 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 galaxies. It extends more in some directions than others, and is not circular. This is evidence that the Virgo Cluster is still forming. (McCall al. 2024)

eROSITA’s past work and future

eROSITA has made a huge leap forward in X-ray astronomy since its launch in June 2019. It began work in October of that year, providing high-resolution X-ray vision of the cosmos. As it scanned the sky, it glimpsed changes in a distant quasar called SMSS J114447.77-430859.3.

These changes provide some clues to the growth of the black hole at the heart of the quasar. It observed changes in brightness variations at the heart of the quasar, indicating that the black hole is gobbling up some of the material that ends up in its event horizon. Other material escapes in the form of strong winds.

The instrument also discovered a newly formed black hole in the early universe and mapped the existence of hot gas surrounding our own Milky Way Galaxy. The instrument first turned on on October 22, 2019. It is currently in safe mode and technicians are assessing its health and status.

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

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