Stunning simulation shows black hole feasting on a wayward star

It turns out that black holes are incredibly messy eaters.
Chris Young
An artist's impression of a black hole.
An artist's impression of a black hole.

Fulya Kıroğlu / Northwestern University 

A team of scientists simulated a black hole devouring a star.

It turns out that black holes are extremely messy eaters, as they take small chunks out of stars before flinging the remains far into the cosmos.

We know this thanks to a new study by researchers at Northwestern University, who simulated the dying moments of a star spiraling into an intermediate-mass black hole.

Simulating a black hole feasting on a star

In their simulations, the researchers flung Sun-sized stars at black holes of varying masses. They found that, when a star approaches an intermediate black hole, it initially gets caught in its orbit.

Like an asteroid orbiting our Sun, that star will then make several close approaches to the black hole. Each time, it will have a chunk removed until nothing is left but the star's dense core. When only the core remains, the black hole ejects what's left far out into the cosmos and outside the black hole's sphere of gravitational influence.

The researchers, who published a paper in The Astrophysical Journal, believe their findings could help astronomers to spot intermediate black holes feasting on stars in the future.

"We obviously cannot observe black holes directly because they don't emit light," Northwestern's Fulya Kıroğlu, who led the study, explained in a press statement. "So, instead, we have to look at the interactions between black holes and their environments. We found that stars undergo multiple passages before being ejected. After each passage, they lose more mass, causing a flair of light as it's ripped apart. Each flare is brighter than the last, creating a signature that might help astronomers find them."

The elusive intermediate-mass black hole

Astrophysicists have so far proven the existence of lower- and higher-mass black holes, but they have not been able to do so for intermediate black holes so far.

Intermediate black holes are believed to be 10 to 10,000 times more massive than lower-mass stellar remnant black holes, but as large as supermassive black holes.

"Their presence is still debated," Kıroğlu said. "Astrophysicists have uncovered evidence that they exist, but that evidence can often be explained by other mechanisms. For example, what appears to be an intermediate-mass black hole might actually be the accumulation of stellar-mass black holes."

Thanks to the new computer simulations of Kıroğlu and colleagues, we now know that stars could orbit an intermediate-mass black hole roughly five times, producing a massive flash each time it makes its closest approach. That may provide just the hint astrophysicists need to pour over archival data with machine learning algorithms in order to pinpoint a region of space that might be home to the elusive category of space giant.

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