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Medium-sized black holes eat stars like messy toddlers

Elusive intermediate-mass black holes take a few bites, then eject the leftovers

If they exist, intermediate-mass black holes likely devour wayward stars like a messy toddler — taking a few bites and then flinging the remains across the galaxy — a new Northwestern University-led study has found.

In new 3D computer simulations, astrophysicists modeled black holes of varying masses and then hurled stars (about the size of our sun) past them to see what might happen.

When a star approaches an intermediate-mass black hole, it initially gets caught in the black hole’s orbit, the researchers discovered. After that, the black hole begins its lengthy and violent meal. Every time the star makes a lap, the black hole takes a bite — further cannibalizing the star with each passage. Eventually, nothing is left but the star’s misshapen and incredibly dense core.

At that point, the black hole ejects the remains. The star’s remnant flies to safety across the galaxy.

Not only do these new simulations hint at the unknown behaviors of intermediate-mass black holes, they also provide astronomers with new clues to help finally pinpoint these hidden giants within our night sky.

“We obviously cannot observe black holes directly because they don’t emit light,” said Northwestern’s Fulya Kıroğlu, who led the study. “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 its ripped apart. Each flare is brighter than the last, creating a signature that might help astronomers find them.”

Continue to the full Northwestern News story.

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