Astronomers Are Watching a Black Hole Tear a Star Apart in Another Galaxy

Astronomers detected a massive outpouring of energy from a distant galaxy 10 years ago, which would usually mean a supernova event — the death of a star. The galaxy in question is actually two galaxies colliding, so the region known as Arp 299 is rich with supernovae. However, the signal changed in unexpected ways over the last decade, and scientists now believe this is a result not of a supernova, but of a star being gobbled up by a black hole.

In a new study, astronomers claim a star with around two solar masses came apart at the seams when it encountered a black hole with the mass of 20 suns. The original event (about 150 million light years distant) showed up in the sky to be detected by the William Herschel Telescope in the Canary Islands. It was bright across much of the electromagnetic spectrum, which is what you’d expect from a supernova. The signal eventually changed in ways that made scientists wonder if this was more than just another supernova.

When a star ventures too close to a black hole, it won’t necessarily fall in right away. The black hole may pull material away from the star over the course of many years, creating an accretion disc of matter spiraling into the event horizon. Some of that material becomes a jet, ejecting particles from the black hole’s vicinity at a significant fraction of the speed of light. Astronomers have never had the luxury of observing a so-called “tidal disruption event” in real time, so teams around the world were keen to confirm.

It took years of observations with multiple instruments like the Very Long Baseline Array (VLBA) and Spitzer Space Telescope, but astronomers recently confirmed they are looking at a tidal disruption event. Observations showed that the object dropped in the X-ray and visible spectrums over time while staying active in radio and infrared. That’s what you’d expect from a black hole as it tears apart a star.

Scientists believe tidal disruption events are common throughout the universe, but much of the energy is obscured by clouds of dust and gas around back holes. This event might just have peeked through a gap in the clouds, so perhaps there are many more tidal disruption events happening in this region of space. By surveying the sky in infrared and radio spectrums, we could detect more of these objects.