Black holes are difficult to understand. Ours is in the center of a large galaxy. When a star gets too close to the black hole, it causes it to tear the star apart as it feeds on it. Even the biggest stars can't resist.
Black holes didn't start out that big. Their mass was achieved by merging with other black holes and by accretion.
One way to fill large voids in our understanding of how SMBHs grow and evolve is to watch black holes.
Black holes can't be directly observed because not even light can escape them. Black holes have total control over their surroundings, and as they bend matter near them to their will, that matter creates a spectacle of light.
Astronomers are able to see all that light. NuSTAR is one of the telescopes. The telescope was launched in 2012 It looks at the x-rays from a source other than the sun.
There is a new study in the Astrophysical Journal. The title of the event is The Tidal Disruption event. A graduate student at Caltech is the author.
A black hole tears apart a star that is too close. AT2021ehb is the name of a TDE that took place in a galaxy about 250 million light years away from Earth. Our Sun is about 10 million times larger. The fifth example of a black hole destroying a star gave astrophysicists an opportunity to study TDEs with telescopes.
Black holes are often surrounded by disks of material. The gas accumulates over a long period of time. The disks can be billions of miles wide, and as they swirl towards the black hole, the gas heats up and can surpass the entire universe. Without the disk and its light, a black hole is just a black hole.
The light from that TDE is still visible even though the disk is not as bright as it could be. It can take as little as a few weeks or months for the TDE to be finished. Astrophysicists are interested in events that can be observed in their entirety.
There was a rise in x-ray emissions after the black hole ripped apart the star. The x-rays show that the TDE was making super-heated material above the black hole. NuSTAR is here. NuSTAR is best at observing x-rays in detail, and AT2021ehb is close enough to give astrophysicists a chance to observe the corona and what happens to stellar material before a black hole completely devours it.
The region is tightly packed. The gas is heated to extreme temperatures and stripped of electrons. The corona is made of billions of degrees of heat. The magnetic field lines in the accretion disk are thought to be the cause of its formation. In the outer regions of the disk, the lines are predictable, but in the field lines are unpredictable. Particles form the superheated corona and emit x-rays when they are accelerated.
Suvi Gezari is an astronomer at the Space Telescope Science Institute. They give us a glimpse of the real-time feeding of a massive black hole.
The material from the corona is carried by a black hole when it emits its jets. There has been a debate for twenty years about whether the corona and the jet were the same thing. The jet follows from the corona after they arise.
Observations of a TDE were not used in that study. The link between a star that got too close to a black hole and the creation of the corona was shown in this study.
The side of the star closest to the black hole is torn apart first. A stream of gas that flows to the black hole's accretion disk begins to swirl around the hole after the star is destroyed. The stream of material hits the hole. The scientists think that the collision creates waves of gas. UV and X-rays are emitted by those flows.
Light emissions are quieted down as the material settles down. The star had to be torn apart for the material to heat up and then cool down. The first TDE was spotted by the Zwicky Transient Facility. The Swift Observatory andNICER telescope made their own observations. They give more complete pictures of complex astrophysical events when they work together.
Something strange happened after the initial period of heating up and cooling down.
NASA's NuSTAR did its own observations after the black hole destroyed the star. Scientists were surprised when there were no jets. The jets come from the opposite side of a black hole.
The X-ray emission without a jet present is spectacular because it means we can disentangle what causes jets and what causes coronae. The observations of AT2021ehb are in agreement with the idea that magnetic fields have something to do with how the corona forms.
AT2021ehb is different from the others. It is brighter than any other T DE. 300 million degrees is the brightness peak. The first hard X-ray spectrum of a non-jetted T DE up to 30 keV was obtained by the researchers.
The picture of what is happening in these complex events is painted by the light's behavior. TDEs are linked to the formation of a black hole's corona. astrophysicists need more observations of T DEs to understand the relationships between all three
The lead author is looking for more TDEs. Black holes, TDEs, coronae, and jets can be better understood with more data from telescopes.
The people want to find as many as possible.
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