For decades, astronomers have predicted that, in approximately 4.5 billion years, our galaxy will merge with the nearby Andromeda galaxy in a massive collision that will dramatically reshape our immediate cosmic neighborhood. But what if this doomed encounter isn’t inevitable and each galaxy will remain intact?
Previous research suggested that the upcoming collision between the two galaxies was inevitable, but a new study claims there’s a 50% chance the Milky Way could narrowly avoid Andromeda. The study, available on the preprint server arXiv, questions the certainty of a galactic collision, as hinted by its title: “Apocalypse When?” The paper is currently undergoing peer review.
For more than a century, scientists have observed the Andromeda galaxy, which is located 2.5 million light-years away, slowly sneaking up on the Milky Way in what has been predicted to result in a head-on collision. “The universe is expanding and accelerating, and collisions between galaxies in close proximity to each other still happen because they are bound by the gravity of the dark matter surrounding them,” according to NASA.
In 2021, NASA’s Hubble telescope captured images of stars in Andromeda, which scientists then analyzed to determine that the galaxy is moving towards the Milky Way at a speed of 250,000 miles per hour. From there, scientists claimed they could predict with certainty the head-on encounter scheduled in about 4 billion years. At the time, computer simulations suggested that it would take an additional two billion years for the two galaxies to fully merge with each other and reshape into one elliptical galaxy, with our solar system flung into a completely new region in relation to the galactic core.
The researchers behind the new study, co-authored by Till Sawala, an astrophysicist at the University of Helsinki, used recent observations from the Gaia and Hubble telescopes to analyze the motion and mass of the largest galaxies in the Local Group: Andromeda (the largest), the Milky Way, Triangulum, and the Large Magellanic Cloud. The team then plugged those calculations into a simulation that predicted the galaxies’ evolution over the next 10 billion years.
Through the simulations, the team found that the Milky Way and Andromeda only merged in slightly less than half of the scenarios. “As it stands, proclamations of the impending demise of our Galaxy appear greatly exaggerated,” the researchers wrote in the study.
The study also suggests that upcoming Gaia data will further refine measurements of the motion and mass of Local Group galaxies, and that more work is required before the fate of our galactic neighborhood can truly be determined.
