Apocalypse Later

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For over a century, astronomers have predicted that our galaxy, the Milky Way, will one day collide with another, Andromeda. Meanwhile, all studies have claimed that we will not live to see the grand spectacle as it will occur billions of years in the future.

Now, a breakthrough piece of research found that the merger might not happen at all – but if it did it would be in about 10 billion years’ time, and not five billion as previously projected. The odds are those of a coin toss, scientists said.

We still know too little about our galaxy and its neighbors to establish with absolute certainty what will happen and when, researcher Till Sawala and his colleagues wrote.

Their study added to a body of knowledge created in 1912 when astronomer Vesto Slipher remarked that the light emitted by Andromeda was blue-shifted – signaling movement toward Earth. In 2008, other researchers predicted that the merger should happen in five billion years.

However, to have more precise predictions, astronomers need a full picture that includes the speed of Andromeda’s stars, a complicated task given the galaxy’s distance, 2.5 million light-years away.

Two space telescopes, NASA’s Hubble and Europe’s Gaia, can help produce a more accurate map of Andromeda, the Milky Way, as well as two other galaxies in the vicinity: M33 and the Large Magellanic Cloud. All four are part of a set known as the Local Group.

Sawala and his team plugged data from both telescopes into simulations, revealing that the odds of the collision happening change depending on the inclusion of either M33 or the Large Magellanic Cloud.

In the first case scenario, there’s a two-thirds chance the collision will occur. But in the second, “the orbit of the Large Magellanic Cloud runs perpendicular to the Milky Way-Andromeda orbit and makes their merger less likely,” the study said. In all, it’s a 50-percent chance.

Nonetheless, Local Group galaxies are bound to end up piled together. If the universe keeps expanding, the single galaxy they would form could become a lonely cluster of stars in a radius of billions of light-years, Science wrote.