Some of the hottest and most energetic phenomena in the universe glow brightly in X-rays. Studying that part of the electromagnetic spectrum is not an easy task, but observatories in space have accomplished this feat in the last six decades.
Now, a space telescope launched in July 2019 has just completed its first survey. For months, the eROSITA telescope aboard the Spektr-RG space observatory has been scanning the entire sky, collecting observations for the deepest study of the entire sky at X-ray wavelengths.
The map is undoubtedly the deepest X-ray view in the universe, with more than 1 million objects observed and single-handedly doubling the number of X-ray sources we knew about. Sources range from the hot crowns of nearby stars to distant supermassive black holes in an absorption frenzy.
Clusters of galaxies in the new map will be used to track the growth of cosmic structures and constrain cosmological parameters.
“This whole-sky image completely changes the way we view the energetic universe,” said Peter Predehl, an astronomer at the Max Planck Institute for Extraterrestrial Physics and a leader of the work. “We see a lot of detail – the beauty of the images is really impressive .”
The map shows the structure of hot gas in the Milky Way and the surrounding environment, whose properties are key to understanding the history of the formation of our galaxy. It also reveals stars with strong magnetically active hot crowns; binary stars that contain neutron stars, black holes, or white dwarfs; and spectacular supernova remnants in our galaxies and other nearby galaxies, such as the Magellanic Clouds.
X-rays are invisible to the naked eye, like radio waves, hence the sky in X-rays looks very different from what we see when we look over our heads at night. Also, unlike radio waves, X-rays are mostly blocked by Earth’s atmosphere, so the only way we can study them is by sending telescopes into space.
Map creation
The Spektr-RG space observatory is located at one of Earth’s Lagrange points, a gravitationally stable pocket created by the interaction between the Earth and the Sun, approximately 1.5 million kilometers away.
The instrument collected 182 days of data, each exposure between 150-200 seconds, totaling 165 gigabytes. Each day, the team connected to the satellite to download what it had collected. Then all that raw data had to be processed and gathered. It has been an incredibly painstaking job.
“With a million sources in just six months, eROSITA has already revolutionized X-ray astronomy, but this is just a taste of what is to come,” explained Kirpal Nandra, head of the high-energy astrophysics group at MPE. “This combination of sky area and depth is transformative. In the coming years, we will be able to explore even further, to where the first giant cosmic structures and supermassive black holes were formed. “
Referencia: eRosita. Max Planck Institute for Extraterrestrial Physics.
