The Milky Way and Andromeda are on a collision course

Andromeda is approaching us at about 110 km per second. In roughly four billion years the two galaxies will merge into one giant elliptical galaxy. Andromeda is the nearest large galaxy and it is moving toward us at about 110 kilometres a second. Gravity has been pulling the two together for billions of years, and eventually they are expected to meet and merge. Galaxies are mostly empty space, so almost no stars would actually hit one another — the merger reshapes orbits rather than causing collisions, and the Sun would simply be flung onto a new path. Compressed gas would trigger a burst of star formation, and the two central black holes would eventually spiral together. Recent work has made the outcome much less certain than the textbook version: accounting for the pull of nearby galaxies, some analyses put the odds of a merger within the next 10 billion years at closer to a coin flip.

The Milky Way and Andromeda are on a collision course

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