Milkomeda: the future "supergalaxy"

A new international study, coordinated by a team of the Department of Physics of Sapienza University of Rome, carried out sophisticated numerical simulations to predict the cosmic times in which our galaxy will collide with Andromeda until it merges into a single "supergalaxy". The results, which have shed new light on the fate of our star system, have been published on the Astronomy and Astrophysics journal

Our galaxy belongs to a cluster of galaxies called the Local Group, consisting of about seventy star systems, most of which are relatively small in size. The centre of mass of the Local Group is located in a point between the Milky Way and the Andromeda Galaxy, which are, together with the galaxy M 33, its main components.

Modern astronomical observations suggest the existence of supermassive black holes within both the Milky Way and Andromeda, with a mass millions of times greater than that of our Sun. Furthermore, the position and relative speed of the two galaxies suggest a future collision between the two systems; a question mark hangs over their destinies and those of their respective black holes.

Today, a new study coordinated by the Department of Physics of Sapienza University of Rome, in collaboration with the University of Heidelberg (Germany) and the Northwestern University (USA), provides the answers to these questions and identifies the cosmic times in which the clashes between the two galaxies and their black holes will occur.

The paper, published on the Astronomy and Astrophysics journal, suggests that in about 10 billion years the Milky Way and Andromeda will merge into a single "supergalaxy", which could be called Milkomeda.

The researchers have reached these results through sophisticated numerical simulations, which have been carried out with a high-performance calculation system available to the group of theoretical astrophysics (ASTRO) of the Department of Physics of Sapienza University.

"In a time that is indeed long compared to human times, but not enormous compared to cosmic ones, the two galaxies will collide and merge into a single supergalaxy, Milkomeda - says Roberto Capuzzo Dolcetta of Sapienza. "The first collision between the galaxies will take place in 4 billion years and the fusion in about 10 billion years, a time curiously similar to the estimated age of the Universe, that is from the Big Bang to the present day."

The researchers, thanks to the obtained data, could also predict that, following the galactic collision and fusion, the respective supermassive black holes of the two galaxies will orbit each other.

"This means – concludes Roberto Capuzzo Dolcetta - that in a time a thousand times shorter than that necessary for the collision of the "mother" galaxies, the black holes will collide in turn creating an extremely powerful explosion of gravitational waves, billions of times greater than those recently identified by the large gravitational interferometric observers of the international collaboration LIGO-VIRGO in the United States and Italy."

References:

Future merger of the Milky Way with the Andromeda galaxy and the fate of their supermassive black holes - Riccardo Schiavi, Roberto Capuzzo-Dolcetta, Manuel Arca-Sedda, and Mario Spera - Astronomy and Astrophysics DOI /10.1051/0004-6361/202038674