What happens when a star gets too close to a supermassive black hole? The real story is that the black hole will swallow it forever. Along the way, some of its material becomes incredibly hot and emits enormous amounts of radiation, mostly in the form of X-rays. Such an explanation is not wrong, but it is incomplete.
Thanks to a team of researchers at the University of California, Berkeley, there is much more to the story. To study the absorption of a star by a black hole, that is, the event of gravitational absorption, they used a specialized spectrograph from the Lick Observatory. The results of the observation were completely unexpected.
Spinning a Doomed Star
A supermassive black hole is located at the center of most galaxies in the universe. When a star approaches it, strange things happen. Gravitational pull disrupts the star and pulls some of its material toward itself—a process called “spaghettification.”
Recent studies of gravitational collapse events indicate that other things are going on at the same time. For example, strong winds blow outward from the event site, carrying some of the matter of the doomed star into space. It’s all just one part of the weirdness.
“One of the craziest things a supermassive black hole can do is to pull a star apart with its enormous gravitational forces. Such events of gravitational capture of stars are among the rarest events thanks to which astronomers know about the presence of supermassive black holes at the center of galaxies and also measure their characteristics,” says team member Web in Liu, assistant professor of astronomy at the University of California, Berkeley.
However, as the researcher points out, due to the extreme complexity of numerical simulations of such events, astronomers still do not know about the complex processes that occur after a gravitational capture event.
This is why the study of a doomed, real star is important. The Berkeley team studied one such star that is too close to a black hole; The event was called AT2019qiz.
The disaster occurred in a spiral galaxy about 215 million light-years from Earth in the direction of the Eridanus constellation. When the star started spiraling into the accretion disk, it was torn apart.
After that, something amazingly unexpected happened. It took a special effort to see this.
A polarized view of the action
Since the eclipse was quite bright in optical light, the team of researchers decided to study it in polarized light to better understand what was really going on there. Polarized light waves travel in one plane, which reduces the strength of the light.
In this case, the use of polarized light made it possible to see the following events of the star’s collapse. As a rule, it is not visible in other ways. Based on observations of other such events, they also did not see the expected number of X-rays. I mean, what happened?
In the case of AT2019qiz, spectropolarimetric observations revealed that much of the star’s material did not end up in the hungry belly of the black hole. Part of it was scattered in space. Strong winds from the black hole also produced a spherically symmetric high-velocity cloud of stellar debris. The researchers found that it was moving at a speed of 10,000 km per second, which was quite unexpected for them.
“This is the first time anyone has been able to determine the shape of the gas cloud around a Gravitational Spaghetti star,” said Alex Filippenko, a professor of astronomy at the University of California, Berkeley, and a member of the research team.
The lacerated star hints at other such events
This unique view of stellar collapse explains why astronomers have not seen large amounts of high-energy X-rays in this and other such gravitational collapse events. Strong winds created a cloud that blocks much of the high-energy radiation produced by the event.
According to the author of the study, Koshora Patra, other evidence of wind-generated during this event has been observed before.
“I think the polarization study made the evidence much stronger that you can’t get a spherical geometry without a sufficient amount of wind.” In this case, the interesting fact is that a significant part of the matter of the star spiraling towards the black hole was not absorbed into the black hole, but flowed out,” says Patra.
What will happen next?
Using polarized light offers an important tool for studying what happens when other stars collide with supermassive black holes. It also gives astronomers access to events in the black hole’s accretion disk. It is not an easy task at all.
“These takeover events happen so far back that they cannot really be resolved; Therefore, you need to study the geometry of the event or the structure of these explosions. However, the study of polarized light helps us to get some information about the distribution of matter in the explosion, and in this particular case, the shape of the gas and accretion disk around the black hole,” says Filippenko.
Polarized light from such bright events is a valuable tool for studying them.
Prepared according to Universe Today.