Black Holes Devour Stars Whole When Galaxies Collide

(CN) – Cosmic events in which stars are ripped apart by supermassive black holes occur 100 times more frequently than previously thought.

These tidal disruption events, or TDEs, had only been found in larger surveys that observed several thousands of galaxies, leading scientists to believe they were particularly rare.

But astronomers at the University of Sheffield were able to identify such stellar cannibalism in a survey of just 15 galaxies, publishing their findings in the journal Nature Astronomy.

“Each of these 15 galaxies is undergoing a ‘cosmic collision’ with a neighboring galaxy,” co-author James Mullaney said. “Our surprising findings show that the rate of TDEs dramatically increases when galaxies collide.”

Mullaney believes these collisions lead to stars forming closer to the central supermassive black holes in the galaxies as they merge together, which increases their risk of being ripped apart in a TDE.

Identifying a supermassive black hole can be a challenge for scientists, as its gravitational force is too strong for light to escape. This requires astronomers to search for the vibrant flares of energy produced during TDEs.

The team first observed the 15 colliding galaxies in 2005, but they noticed that one galaxy – F01004-2237 – looked strikingly different when they reviewed it again in 2015, according to study co-author and University of Sheffield PhD student Rob Spence.

“This led us to look at data from the Catalina Sky Survey, which monitors the brightness of objects in the sky over time,” Spence said. “We found that in 2010, the brightness of F01004-2237 flared dramatically.”

Lead author Clive Tadhunter said the results for F01004-2237 suggest that TDE events will become more common in the Milky Way galaxy when it eventually merges with the nearby – in cosmic terms – Andromeda galaxy in about 5 billion years.

“Looking towards the center of the Milky Way at the time of the merger we’d see a flare approximately every 10 to 100 years,” Tadhunter said. “The flares would be visible to the naked eye and appear much brighter than any other star in the night sky.”

 

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