Recent observations of a black hole devouring a rogue star may help scientists understand more complex black hole feeding behaviors. Multiple NASA telescopes recently observed a massive black hole tearing apart an unlucky star that got too close to it. Located about 250 million light-years from Earth at the center of another galaxy, it was the fifth-closest example of a star-destroying black hole ever observed. Once the black hole’s gravity completely ripped the star apart, astronomers saw a dramatic increase in high-energy X-ray light around the black hole. This indicated that as stellar material was drawn towards its doom, it formed an extremely hot structure above the black hole called the corona.
NASA’s NuSTAR (Nuclear Spectroscopic Telescopic Array) satellite is the most sensitive space telescope capable of observing these wavelengths of light, and the proximity of the event provided an unprecedented view of the formation and evolution of the corona, according to a new study published in The Astrophysical Journal. The work demonstrates how the destruction of a star by a black hole, a process formally known as a tidal disruption event, could be used to better understand what happens to material captured by one of these giants before it is completely devoured. Most of the black holes that scientists can study are surrounded by hot gas that has built up over many years, sometimes millennia, and forms disks billions of kilometers wide. In some cases, these disks outshine entire galaxies. Even around these bright sources, but especially around much less active black holes, a single star stands out, tearing itself apart and consuming itself.
And from start to finish, the process often takes just a few weeks or months. The observability and short duration of tidal disruption events make them especially attractive to astronomers, who can decipher how the black hole’s gravity manipulates the material around it, creating incredible light shows and new physical features. “Tidal disruption events are a kind of cosmic laboratory,” says study co-author Suvi Gezari, an astronomer at the Space Telescope Science Institute in Baltimore. “They are our window into a real-time feed from a huge black hole lurking in the center of a galaxy.” a startling sign The focus of the new study is an event called AT2021ehb, which took place in a galaxy with a central black hole about 10 million times the mass of our Sun. During this tidal disruption event, the nearest side of the star The black hole was trapped tighter than the far side of the star, pulling everything apart and leaving nothing but a stretched-out noodle of hot gas.
Scientists believe that the stream of gas is whipped around a black hole during such events, colliding with itself. This is thought to create shock waves and outward gas flows that generate visible light as well as wavelengths not visible to the human eye, such as ultraviolet light and X-rays. The material then begins to settle into a disk that rotates around the black hole like water flowing down a drain, and the friction generates low-energy X-rays. In the case of AT2021ehb, this series of events took place over just 100 days. An especially short event The event was first seen on March 1, 2021 by the Zwicky Transient Facility (ZTF), located at the Palomar Observatory in southern California. It was later studied by NASA’s Neil Gehrels Swift Observatory and Neutron star Interior Composition Explorer (NICER) telescope (which observes longer X-ray wavelengths than Swift). Then, around 300 days after the event was first detected, NASA’s NuSTAR began observing the system. Scientists were surprised when NuSTAR detected a corona, a cloud of hot plasma or gas atoms stripped of electrons, since coronas typically appear with jets of gas flowing in opposite directions from a black hole.
Source
https://iopscience.iop.org/article/10.3847/1538-4357/ac898a