'Not so fast': NASA shares a big update on 'end of the world' doomsday prediction

For over a century, scientists believed that a cosmic catastrophe awaited our galaxy. In 1912, astronomers noticed that the Andromeda galaxy appeared to be on a collision course with the Milky Way. In 2012, NASA's Hubble Space Telescope confirmed that Andromeda’s sideways movement was minimal, reinforcing the idea of a direct hit in about 4 to 5 billion years. But now, a new study says that might not be the case after all.

Revisiting the Future of the Milky Way

A new paper published in Nature Astronomy presents a very different outlook. Using data from both NASA’s Hubble Space Telescope and the European Space Agency’s Gaia observatory, astronomers have re-examined the previous prediction. The updated study, led by University of Helsinki astronomer Till Sawala, suggests the future isn't as certain as once believed.

“We have the most comprehensive study of this problem today that actually folds in all the observational uncertainties,” said Sawala.

The research team, which includes scientists from Durham University, the University of Toulouse, and the University of Western Australia, ran computer simulations to understand the long-term behavior of the Milky Way and Andromeda. Their conclusion? There’s about a 50% chance of a collision occurring within the next 10 billion years.

How Likely Is a Collision?

To reach this finding, astronomers considered 22 variables and ran 100,000 simulations stretching far into the future. This method, known as Monte Carlo simulation, helps model outcomes with complex variables.

“Because there are so many variables that each have their errors, that accumulates to rather large uncertainty about the outcome, leading to the conclusion that the chance of a direct collision is only 50% within the next 10 billion years,” said Sawala.

He added that while the Milky Way and Andromeda might appear destined to merge, “they could still go past each other.”

Other Galaxies Add to the Complexity

The study also took into account the influence of other nearby galaxies — Andromeda’s massive satellite M33, and the Milky Way’s Large Magellanic Cloud (LMC). Both galaxies add gravitational forces that impact the trajectory and motion of the Milky Way and Andromeda.

“The extra mass of Andromeda’s satellite galaxy M33 pulls the Milky Way a little bit more towards it. However, we also show that the LMC pulls the Milky Way off the orbital plane and away from Andromeda. It doesn't mean that the LMC will save us from that merger, but it makes it a bit less likely,” Sawala explained.

Still a Small Chance of a Sooner Collision

Even with the revised outlook, a head-on collision remains possible, albeit unlikely. The new data still allows for a 2% chance that the two galaxies might collide in just 4 to 5 billion years — a scenario similar to earlier predictions.

However, Earth’s habitability will be long gone by then, as scientists estimate the Sun will make the planet too hot for life within 1 billion years, and will itself burn out in about 5 billion years.

A Universe of Unknowns

The study reflects how astronomical predictions continue to evolve as better data becomes available. “Even using the latest and most precise observational data available, the future of the Local Group of several dozen galaxies is uncertain,” said Sawala. “Intriguingly, we find an almost equal probability for the widely publicized merger scenario, or, conversely, an alternative one where the Milky Way and Andromeda survive unscathed.”

NASA and ESA’s Hubble Space Telescope, which has been operational for over 30 years, remains a cornerstone of space exploration. The ongoing collaboration between international teams continues to reshape what we know — and what we think we know — about the future of our galaxy.