A black hole tears down a star, leaving a long string of star material, which then wraps itself around the black hole. (Credit: NASA//CXC/M. Weiss
Filaments of material wrapped around a supermassive black hole have been spotted for the first time suggesting a star trapped by the black hole's gravity has just been destroyed by ”spaghettification”.
Astronomers believe that the effect more commonly known as tidal disruption, takes place because the black hole's gravity pulls more strongly on the side of the star closer to the black hole. The black hole first rips the star apart and then sucks in its matter , turning the star into a long filament in the process.
Previously, the only evidence of such a situation where a star met a violent demise venturing too close to a galaxy's center, came in the form of short bursts of electromagnetic radiation that astronomers occasionally observed emanating from supermassive black holes.
However, it wasn't until now that scientists have seen evidence of the actual physical filament from a star in the black hole's vicinity. In this new study , published in the journal Monthly Notices of the Royal Astronomical Society on March 24, a team of astronomers from the Netherlands Institute for Space Research (SRON) and Radboud University in the Netherlands has successfully detected such a spaghettified star in spectral absorption lines around the poles of a distant black hole.
Absorption lines are unusually dark lines detected in the otherwise continuous spectrum of electromagnetic radiation emitted by a source, in this case a black hole. These lines appear when material that absorbs part of the electromagnetic radiation (in this case the spaghettified star) obscures the source.
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The astronomers observed the spectral absorption lines when looking at the black hole's rotational pole. The observation suggested that there was a strand of material wrapped multiple times around the black hole like a yarn ball, the scientists said in a statement on April 23. The team believes that this material is the torn star as it orbits around the black hole before disappearing inside of it.
Disks of accreted matter are known to exist around black hole's equators. Made of material that is drawn to but not yet swallowed up by the black hole, the disk orbits around the equator at a very high speed, emitting heat, X-rays and gamma-rays in the process.
The authors of the current study, however, claim that the material they were looking at wasn't part of the accretion disk.
"The absorption lines are narrow," said Giacomo Cannizzaro, the lead author of the paper. "They are not broadened by the Doppler effect, like you'd expect when you would be looking at a rotating disk."
The Doppler effect, caused by the fast motion of the material in the accretion disk, stretches or shrinks the electromagnetic waves depending on whether the source is moving towards or away from the observer. As a result, the light emitted by the part of the accretion disk that is moving away from Earth would be brighter. But the scientists saw no evidence of that.
The researchers also said in the statement that they knew they were facing the black hole's pole because they could detect X-rays. "The accretion disk is the only part of a black hole system that emits this type of radiation," the statement said. "If we were looking edge-on, we wouldn't see the accretion disk's X-rays."
Millions and even billions of times heavier than the sun, supermassive black holes are believed to lurk at the center of most galaxies. They grow over billions of years, swallowing up everything that falls into their gravitational embrace. Astronomers can detect black holes thanks to the bright X-rays they emit as they gorge on gas and matter from their surroundings.
Stars that orbit in the central parts of galaxies might occasionally wander so close to the black holes that they get trapped by their gravity. They get pulled closer and closer to the black hole and eventually die a premature death by spaghettification.
dCLCp on May 7th, 2021 at 15:19 UTC »
I wonder if there are unique abilities or phenomenon that we can use spaghetification for in astronomy? I mean in the sense that we use gravity lensing to detect much older galaxies or to see things much "further" away.
Does having thin brightly lit strands of a star being gobbled up provide more information about the shape or behavior of blackholes or stars or reveal information "behind" the star and blackhole in novel ways like with gravity lensing?
Often times a unique or interesting discovery becomes the groundwork for the next and besides the cosmological ramifications that we get from this observation, I wonder if there are broader techniques that can be derived from this?
Andromeda321 on May 7th, 2021 at 15:18 UTC »
Astronomer here! I actually study this object myself and have a paper on it going through the referee process right now, and know the guys who have been working on this!
AT 2019dsg is a Tidal Disruption Event (TDE), which is when a star wanders too close to a supermassive black hole and gets ripped apart by tidal forces. It was discovered in May 2019 by an optical survey and was 230 Mpc (~750 million light years) from us, but stood out because it was really bright in optical- like, top 3% of all TDEs or some such. Obviously the question then is why, and I don't think anyone had a very good potential explanation there. Here is a really impressive animation though for how AT 2019dsg might have played out!
In particular, there are questions about the "outflow" of TDEs and how the one in AT 2019dsg worked. Specifically, when a TDE happens we think about half the mass of the star falls into the event horizon, and half gets into some sort of accretion disk and outflow (a spherical shockwave like a supernova, or in very rare cases a relativistic jet). Unfortunately this thing is so far away it's not like you can just take a picture of it, and the outflows can be "thick" at specific parts of the spectrum (aka the light is blocked) based on how the physics goes. To date, no one's really been able to get such good sampling of the disc, until this work! So this is really exciting! (So to be clear this is not a new event that the group discovered, and in fact I think this isn't the first time AT 2019dsg has reached the top of /r/space, just this is a new observation of what is going on in it.)
As an aside, one random detail about AT 2019dsg is a group a few months ago that also looked into this event published claiming an association with a neutrino. That would be a really exciting thing if it were true, but assumes certain energies to be feasible... and my own work shows it doesn't appear to be there. Science! My own research is in modeling the radio outflows of AT 2019dsg with the best sampled radio observations from the VLA and ALMA, which we can use to probe the outflow at much greater distances than the innermost accretion disc. If you're interested in that, here is a link to it and a laymen's explanation of my work. But happy to answer any questions you might have about AT 2019dsg in specific or TDEs in general! They're really amazing objects and I'm rather fond of this one!
Edit: when the star is ripped apart, it is done so thoroughly that fusion ends in the star during the TDE.
Edit 2: the photo is accurate to what we simulate these events to look like up close, but is not a “real” picture. This event is far too far away to be anything but a point source (like stars are- no resolution) on Earth. That’s why things like the spectral information are so important!
In-Evidable on May 7th, 2021 at 15:04 UTC »
Random question: what if a big black hole swallows a little black hole?
It seems like in animations I’ve seen, they kinda just blip into one larger black hole. Shouldn’t the larger black hole “spaghettify” the smaller one though?