Astronomers used to believe that stellar cannibalism — called as Tidal Disruptive Events (TDEs) — is a very rare cosmic event at a ratio of one for every 10,000 to 100,000. Surprisingly, it is not the case anymore.
Researchers have found that massive black holes eat stars as much as 100 times more often.
The new study, which was published in Nature: Astronomy on Feb. 27, discovered a star ripped apart by a black hole in a study composed of 15 galaxies. Astronomers consider the sample size of 15 as very small.
Collision Of Galaxies Increases TDEs
TDEs happen when a star is pulled apart by the black hole tidal forces. This occurs as the star makes a close approach to the black hole while in orbit.
Each in the small sample of galaxies is experiencing a "cosmic collision" with a galaxy nearby, James Mullaney, Astronomy lecturer at University of Sheffield and study co-author, said.
The number of TDEs tremendously increases as galaxies collide or merge. This collision, in turn, likely leads to the formation of the large numbers of stars near the center of supermassive black holes of two galaxies as they merge.
Elusive Black Holes
Supermassive black holes are known to be hard to find. They are not visible in ordinary sense because their gravity is so strong that nothing, including light, can escape.
These supermassive black holes become only observable when the stars it ripped apart released energy in a form of flares. The nuclei of these galaxies will shine just like any other stars in the galaxy.
TDEs are useful for scientists to locate invisible black holes and study their strong gravity and how matter is being disposed of.
The researchers "first observed the colliding galaxies in the sample in 2005".
"However, when we observed the sample again in 2015, we noticed that one galaxy - F01004-2237 - appeared strikingly different," Rob Spence, University of Sheffield PhD student and co-author of the study, said.
With the aid of a celestial survey, it was found out that the luminosity of F01004-2237 had increased in 2010.
The observed change of the brightness of the galaxy was a typical characterization of TDEs.
TEDs More Common As Milky Way And Andromeda Merge
The information generated from F01004-2237 during TDEs points to a possibility of more similar cosmic events will happen in the Milky Way galaxy by the time it will eventually merge with Andromeda galaxy 5 billion years from now.
Clive Tadhunter, astrophysics professor and leader of the study, said flares due to TDEs will become more frequent, approximately at a ratio of one in every 10 to100 years, as the two galaxies will merge.