For decades, astronomers have predicted that in about 4.5 billion years, our galaxy will merge with the nearby Andromeda galaxy in a massive collision that will dramatically change our immediate cosmic neighborhood. But what if this doomed collision is not inevitable and each galaxy remains intact?
Previous research suggested that the impending collision between the two galaxies was inevitable, but a new study claims there is a 50% chance that the Milky Way could narrowly miss Andromeda. The study, available on the preprint server arXiv, questions the certainty of a galactic collision, as its title suggests: “Apocalypse When?”
For more than a century, scientists have watched the Andromeda galaxy, 2.5 million light-years away, slowly creep toward the Milky Way, which predictions say would 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 together by the gravity of the dark matter that surrounds them,” NASA said.
In 2021, NASA’s Hubble telescope captured images of stars in the Andromeda galaxy, which scientists then analyzed and found that the galaxy was moving toward the Milky Way at a speed of 250,000 miles per hour. From there, scientists claimed they could confidently predict the head-on collision scheduled to occur in about 4 billion years. At the time, computer simulations suggested it would take another two billion years for the two galaxies to fully merge and reform into an elliptical galaxy, hurling our solar system into an entirely new region in relation to the galactic core.
The researchers behind the new study, which also includes 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, the Triangulum galaxy system, and the Large Magellanic Cloud. The team then used these calculations to create a simulation that predicted the evolution of the galaxies over the next 10 billion years.
Through the simulations, the team found that the Milky Way and the Andromeda Galaxy merged in just under half of the scenarios. “As it stands, proclamations about the impending doom of our galaxy appear greatly exaggerated,” the researchers wrote in the study.
The study also suggests that future Gaia data will further refine measurements of the motion and mass of Local Group galaxies, and that more work is needed before the fate of our galactic neighborhood can be truly determined.
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