Milky Way has 50-50 chance of colliding with neighbor galaxy

The collision of the Milky Way and Andromeda galaxies that scientists believed was inevitable has a much lower probability than previously thought.

The Associated Press reported Monday that astronomers in Finland have determined that our galaxy has a 50-50 chance of colliding with the neighboring Andromeda within the next 10 billion years. The previous theory suggested that the two galaxies had a high probability of colliding within the next five billion years.

“Based on the best available data, the fate of our galaxy is still completely open,” the team wrote in the study, which appeared in Nature Astronomy.

A team led by University of Helsinki researcher Till Sawala simulated all possible scenarios using the latest data from NASA’s Hubble Space Telescope and the European Space Agency’s Gaia star-tracking mission. According to Space.com, the simulation yielded some surprising results.

“A head-on collision is very unlikely, we found a less than 2 percent chance for that,” Sawala said. “In most of the cases that lead to a merger, the two galaxies will indeed fly past each other at first, which will lead to a loss of orbital energy, and subsequently to a merger.

“How close they come on their first passage is very uncertain, however, and if they don’t come very close, meaning if their distance is more than around 500,000 light-years, they might not merge at all," the researcher added.

Sawala said he was not prepared for what his team found.

“In short, the probability went from near-certainty to a coin flip,” Sawala noted.

The study relied on newer and more precise information, and the team took into consideration a “more complete system,” including the potential effects of the Large Magellanic Cloud. The dwarf galaxy is the Milky Way’s largest satellite galaxy, Space.com reported.

Ultimately, the astronomers found that the Milky Way and Andromeda would inevitably collide if the two galaxies’ orbits come close enough to affect a gravitational pull on one another. If they stay well separated, the merger won’t happen.

While the scenarios indicated a less likely merger between the two, they found that the Milky Way is far more likely to cannibalize the Large Magellanic Cloud.

The research indicates that this newly theorized merger is likely to happen over the next two billion years.