Milky Way-Andromeda merger odds rise to 90 percent in 2026 study

September 7, 2026 at 08:43 AM2 min

This digest was compiled by AI from multiple sources — links to the originals are below.

A 2026 study raises the probability of a Milky Way-Andromeda merger to about 90 percent in its preferred model. The estimate follows a 2025 Nature Astronomy paper that put the odds at roughly even over ten billion years. The two galaxies are approaching at about 400,000 kilometers per hour.

Key Facts

A 2026 study raises the Milky Way-Andromeda merger probability to about 90 percent in its preferred model.
The 2025 Nature Astronomy paper led by Till Sawala estimated roughly even odds of a merger within ten billion years.
NASA's 2012 announcement described a nearly head-on encounter around four billion years in the future.
ESA's 2019 Gaia results shifted the first close passage to about 4.5 billion years.
The Milky Way and Andromeda are approaching each other at roughly 400,000 kilometers per hour.

Merger Probability Estimates

The 2025 Nature Astronomy paper led by Till Sawala used Hubble and Gaia observations to estimate roughly even odds that the Milky Way and Andromeda would merge within the next ten billion years. A separate study published in April 2026 raised the merger probability to about 90 percent in its preferred model. The 2025 finding is worth taking seriously, but it should not be read as the final word.

Historical Forecasts

NASA's 2012 announcement described a nearly head-on encounter around four billion years in the future, with the galaxies needing roughly another two billion years to become a single system. ESA's 2019 Gaia results, led by Roeland van der Marel, favoured a less direct collision and shifted the first close passage to about 4.5 billion years. That work used stellar movements to reconstruct the trajectories of Andromeda and Triangulum, also known as M31 and M33.

Orbital Dynamics

The galaxies are closing on each other at roughly 400,000 kilometers per hour, a figure that measures their relative approach but cannot by itself determine how far to one side Andromeda will pass. ESA's 2019 account describes identifying thousands of stars in the two neighbouring galaxies and tracking their movement across the sky. Sawala's team modelled four galaxies—the Milky Way, Andromeda, Triangulum and the Large Magellanic Cloud—and varied the starting measurements within their uncertainties. In their calculations, Triangulum increased the likelihood of a Milky Way-Andromeda merger.