(This article is also available in German)
A research team, using the now-deactivated eRosita space telescope, has discovered a black hole that periodically swallows parts of the same star that survived these “meals”. As the Max Planck Institute for Extraterrestrial Physics (MPE) explains, the “spectacular” event was discovered during a sky survey in an otherwise inconspicuous galaxy a billion light years away. Immense X-ray bursts were observed there a total of three times in a rhythm that repeated about every 220 days. The star lost only a few percent of the mass of our sun and therefore survived the approaches.
Stern withstands immense forces
The sequence of events
When a star gets too close to the supermassive black hole at the center of a galaxy and is ruptured by tidal forces, researchers call it the “Tidal Disruption Event”. They can be observed as bright flashes in the UV and X-ray spectrum, explains the MPE. Because they only occur about every 10,000 years in a galaxy, such events are comparatively rare to observe overall. Recurring outbreaks are therefore less common, and evidence of this has only recently been discovered. In such cases, the stars survive the unimaginable forces, losing only part of their outer layers. The black hole is fed, but does not consume the entire star. By observing such cases, the growth of such black holes could be better researched.
The source now presented, called J0456-20, was found during a survey of the entire sky. eRosita searches for changeable objects and struck gold here in February 2021. Even the observation in the X-ray range suggests that it is the same star that it is gradually dismantling. In addition, the phenomenon was also observed with antennas in Australia in the radio range and other features were found that support this interpretation. In the case of further observations, the physical processes are to be investigated in more detail. It is also an ideal laboratory “to test the general theory of relativity in very strong gravitational fields,” adds eRositas research director Andrea Merloni. A research article on the find has now been published in the journal Astronomy & Astrophysics.
The X-ray telescope eRosita (extended Roentgen Survey with an Imaging Telescope Array) can map the entire X-ray sky with unprecedented depth. It completed its first full survey in mid-2020. It is installed next to the Russian telescope ART-XC on the space probe Spektrum-Röntgen-Gamma (Spektr-RG). Those responsible in Germany decided in early 2022 to switch off the instrument in response to the Russian war of aggression against Ukraine. Since then it has stopped doing research. However, data that has already been collected will continue to be evaluated. A review of the condition of eRosita began in mid-November, had informed the MPE. How long that lasts is unclear.
(mho)
