Evrim Yazgin
Cosmos science journalist
The nearest large galaxy to the Milky Way, Andromeda, probably won’t collide with our home galaxy as previously predicted.
Andromeda is also known as Messier 31, or M31, and about 2.5 million light-years from the Milky Way. Like our own home galaxy, Andromeda is a spiral. It is slightly larger at about twice the diameter of the Milky Way.
Astronomers had long suspected that the 2 galaxies were on a collision course. This seemed to have been confirmed by data from NASA’s Hubble Space Telescope in 2012. The new elliptical galaxy which might be formed out of the possible Andromeda-Milky Way merger was even dubbed “Milkomeda”.
The collision would happen in about 4 or 5 billion years according to simulations.
But new findings in a paper published in Nature Astronomy question how certain we can be that the Milky Way-Andromeda collision will occur at all.
“Here we consider the latest and most accurate observations by the Gaia and Hubble space telescopes, along with recent consensus mass estimates, to derive possible future scenarios and identify the main sources of uncertainty in the evolution of the Local Group over the next 10 billion years,” the authors write.
The Milky Way’s path through the universe is influenced by the gravitational pull of several objects in our Local Group including Andromeda, but also the smaller Triangulum Galaxy (Messier 33, or M33) and superclusters and dwarf galaxies such as the Large Magellanic Cloud, Small Magellanic Cloud, Virgo Supercluster and Lakiakea Supercluster.
The Triangulum Galaxy and Large Magellanic Cloud in particular play a significant role in the fate of the Milky Way and Andromeda galaxies and their likelihood of colliding.
“Although including M33 increases the merger probability, the orbit of the Large Magellanic Cloud runs perpendicular to the Milky Way-Andromeda orbit and makes their merger less probable,” they explain.
The simulations showed that there was nearly a 50% chance that the Milky Way and Andromeda galaxies would not collide at any point in the next 10 billion years.
The astronomers indicate that there remain uncertainties and simplifications in their model. They assumed, for example, that the mass distributions within the galaxies and other structures in the Local Group remain constant over the next 10 billion years.
But their updated simulations, using the latest physics and observations, do throw into considerable doubt whether there will be any collision between the Milky Way and Andromeda. They say there’s a chance that the Milky Way is certain to collide with the Large Magellanic Cloud in about 2 billion years. In any case, we won’t be around to confirm one way or the other.
