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Two ‘Cannibalistic’ Galaxies Have Collided And Produced A Powerful Gravitational Kick

There are cannibalistic galaxies that give out a gravitational kick equivalent to the recoiling of a strong firearm when one feeds on the other.

Research from the University of Colorado Boulder stated that this is so strong that it can shift the orbits of millions of stars and mold the shape of an entire galaxy. This research is published in The Astrophysical Journal Letters.

The Andromeda galaxy was first seen closely in the 1970s. afterward, it was deeply observed with the Hubble Space Telescope. These observations showed a long and oval mass at Andromeda’s center, where astronomers expected to find a circular cluster of stars around the galaxy’s supermassive black hole.

“When galaxies merge, their supermassive black holes are going to come together and eventually become a single black hole,” said Tatsuya Akiba, lead author of the study and a graduate student in astrophysics. “We wanted to know: What are the consequences of that?”

The UC Boulder researchers’ simulations depict that at the time of the collision, the centers of black holes rotate around each other at a high speed till they bump into each other for good. At this collision, “gravitational waves” are created. “Those gravitational waves will carry momentum away from the remaining black hole, and you get a recoil, like the recoil of a gun,” Akiba explained.

The recoil does not cause the stars away. In fact, the gravitational ‘kick’ throws the remaining supermassive black hole traveling through space at speeds of millions of miles per hour. This causes the stars to go out of their orbit and create an asymmetrical shape like the one observed in the middle of Andromeda.    

In a 2019 study, astronomers stated that the Milky Way will likely be eaten by Andromeda in approximately 4 billion years. This leaves us wondering if such collisions will occur with our galaxy in the future.