A new study published in Nature Astronomy by researchers from Durham University calls into question the long-held notion that the Milky Way would collide with its biggest neighbor, the Andromeda galaxy, in 4.5 billion years.
Image Credit: Durham University
Scientists utilized data from NASA's Hubble and the European Space Agency's Gaia space telescopes to model how the Milky Way, Andromeda, and their most massive satellite galaxies would grow over the next ten billion years.
They discovered that there is just a 2% chance that the galaxies will collide in the next 5 billion years, contrary to previous assumptions that a collision was unavoidable within that timescale.
The Milky Way and Andromeda come into contact at least once in around half of the simulated scenarios before losing enough orbital velocity to finally merge.
In most other circumstances, the two galaxies are so far apart that they can continue to evolve unaffected for an extended period of time.
Cosmic Firework
If the Milky Way and Andromeda crash and merge, the researchers discovered that it will most likely occur in 7 to 8 billion years, much later than previously projected.
A collision of this magnitude would be catastrophic for both galaxies, destroying them and leaving behind a spheroidal mass of stars known as an elliptical galaxy.
There may, however, be cosmic fireworks: gas will be funneled to the center and spew massive amounts of radiation when it collapses into a central black hole in the heart of the merger remnant.
Expansion of Possibilities
The study was led by Dr Till Sawala of the University of Helsinki, who also worked as a Postdoctoral Research Assistant at Durham.
He emphasized that, while this new research calls into question the previously assumed future of the galaxy, the new findings do not imply an error in previous projections.
Instead, the team was able to use new data to investigate a considerably wider range of options than ever before.
More Data, More Knowledge
Meanwhile, uncertainties regarding the destiny of the Milky Way and Andromeda may not remain long.
The research team is already looking ahead to the Gaia space telescope, which will soon provide more exact measurements of some of the most important characteristics in galaxies, including Andromeda's transverse motion.
It is amazing that we are able to simulate the evolution of gigantic collections of stars over billions of years and figure out their ultimate fate. This is a testimony to the power of physics allied to the power of large supercomputers.
Carlos Frenk, Study Co-Author and Professor, Institute for Computational Cosmology, Durham University
New study casts doubt on the likelihood of a Milky Way – Andromeda collision
Video Credit: Durham University
Journal Reference:
Sawala, T., et al. (2025) No certainty of a Milky Way–Andromeda collision. Nature Astronomy. doi.org/10.1038/s41550-025-02563-1