A star in a galaxy 250 million light-years away was having a terrible, horrible, no good, very bad day.
It was minding its own business when it was sucked into a black hole and torn to shreds. Light from the event shone out across the Universe as multiple telescopes spotted it.
It's the fifth-closest such event, and the wealth of data obtained could help scientists understand how black holes feed.
Suvi Gezari is an astronomer at the Space Telescope Science Institute. They allow us to see the feeding of a massive black hole in the center of a galaxy.
We've seen enough disruptions to know what happens when a star wanders too close to a black hole. The star comes apart when it is pulled to the point that it comes apart by the tides.
The guts of the dismembered star then stream around the black hole in a chaotic fashion, colliding with itself and causing that glow in multiple wavelength. The process can take weeks or months as the black hole eats the debris.
The debris falls onto the black hole from the outer rim. A corona can form between the inner edge of the accretion disk and the black hole's event horizon.
The region of hot electrons is thought to be powered by the black hole's magnetic field, which acts like a synchrotron to accelerate the electrons to such high energies.
Powerful jets of plasma launch from the black hole's polar regions and shoot corona material out in opposite directions. When material is accelerated along magnetic field lines outside the black hole's event horizon, it blasts off into the stars.
When a tidal disruption event occurs, coronae and jets are usually seen together. When the Zwicky Transient Facility caught the bright flash of a tidal disruption event on 1 March 2021, NASA turned its X-ray observatory and its Swift Observatory to observe the event's evolution The X-ray observatory NuSTAR joined the fun 300 days later.
The culprit was a black hole that was 10 million times the mass of the Sun. It's so far so normal.
Something was odd. There was no sign of jets by any of the observatories. NuSTAR found the presence of a corona. Scientists say this discrepancy is very exciting.
"We've never seen a tidal disruption event with X-ray emission like this without a jet present, and that's really spectacular, because it means we can potentially 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, and we want to know what's causing that magnetic field to get so strong.
Targets such as AT2021ehb make excellent laboratories for studying the formation and evolution of accretion disks and coronae in real time. The researchers hope that they'll be able to find more such disruptions in the future, leading to answers about the role magnetic fields play in the formation of coronae and jets.
A bad day for a star 250 million years ago was a great day for humans.
The research is in a journal.
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