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“What happens when you throw a star at a black hole?” It is not a question we can physically answer here on Earth.
Fortunately, actual black holes and stars cannot be smashed together in the laboratory! However, scientists can use advanced supercomputer modeling to rip apart a black hole and throw a star into a so-called “tidal disruption event” or “TDE.” In doing so, a team of researchers led by Danel Price from Monash University have discovered that the answer to our initial question is that “things get messy.”
“Black holes can’t eat that much,” Price told Space.com. “Much like myself, after a bad curry, not much goes down the black hole, and most of it comes back in the form of violent outflows. We look at this in tidal disturbance events — outflows strong, relatively low and stable. temperature content, and large emission distances.”
If this is not stomach-churning enough, much like a Saturday night misadventure involving alcohol and dodgy buna, wake up black holes surrounded by the regurgitated remains of their meals in a structure called “Edington Cover.”
“We found that the black hole has smothered matter during the disruption. This is new.” Price explained. “It’s an old idea that this should happen, but we were able to show how it happens by simulating the dynamics of the gas.”
Related: The biggest and brightest such event is the ‘death by black hole’ of a massive star
Pasta and curry? No wonder black holes get sick!
TDEs occur when stars venture too close to the supermassive black holes that lie at the heart of all large galaxies.
“Stars collide with each other as they travel through the galaxy, so their orbits are disturbed a little. Just occasionally, once every 100,000 years, a star will collide enough to be bound to the black hole and go towards it,” Price explained. “The key is that stars only get hit a little bit, so like comets falling towards the sun, they tend to fall into parabolic orbits. These are challenging to simulate.”
When the star is too close to the supermassive black hole, the massive gravitational influence of this cosmic titan generates powerful tidal forces with the star that push it horizontally and stretch it vertically.
This process, called “spaghettification” (we know we changed art here, but stick with it), turns the star into bright noodles of stellar material or “plasma.” This wraps the destructive black hole like spaghetti around a fork. From this flattened swirling cloud of superheated plasma called the “accretion disk”, the mass is gradually fed.
The TDE process and the swirling disk of stellar debris around the black hole generate powerful electromagnetic emissions that allow astronomers to study these events.
But there are still mysteries about TDEs that need to be answered.
To address the complexity of TDEs, Price and team conducted the first self-consistent simulation of a star being tidally engulfed by a supermassive black hole to track the evolution of the resulting debris over an entire year using advanced resolved particle hydrodynamics code called “Phantom.”
“Essentially, we threw a star at a black hole inside the computer,” Price said. “Specifically, we spent a long time trying to properly implement the effects of Einstein’s general theory of relativity, which describes spacetime near a black hole.
“Our simulations provide a new perspective on the final moments of stars in the vicinity of supermassive black holes.”
The Phantom simulation showed that stellar debris created during TDE forms an asymmetric bubble around the black hole. As a result of this reprocessing of energy, producing light emissions with lower temperatures and less luminosities.
The team also discovered that this gas moves around the super black hole at speeds of 22 million to 45 million miles (10,000–20,000 kilometers per second), which is about 60,000 times the speed of sound at sea level or about 7% of the speed of sound. light.
“The study helps to explain some obscure properties of the observed TDEs,” Price said. “A good analogy is the human body: when we eat lunch, our body temperature does not change much; that is because we reprocess the energy from lunch into infrared wavelengths.
“TDE is similar; we mostly don’t see the black hole’s stomach eating gas because it’s smeared by material that comes back at optical wavelengths. Our simulations show how this choking happens.”
Energy reprocessing and black hole smoothing in the simulation explains one of the biggest observational mysteries about TDEs, understanding why they emit primarily in optical or visible wavelengths of light rather than X-rays, Price added.
The results also explain many other mysteries about TDE, including why starbursts appear in less light than expected and why this material appears to be moving towards us at a fraction of the speed of light.
Related stories:
— The black hole announces itself to astronomers by violently ripping stars apart
— The black hole that ate it years ago is throwing a ‘spaghetti’ star
— NASA’s X-ray observatory reveals how black holes swallow stars and throw away matter
As for the future, the team’s simulations left much to be desired.
“There’s a lot to explore here. When the Vera Rubin Observatory starts operating, we expect thousands of transient observations over the next decade,” Price said. “We need to try the same type of simulation for all types of stars and different masses of black holes so that it is applicable to different observed events.”
The team’s research is published in the Astrophysical Journal Letters.
