“The collision between our galaxy and the [Large Magellanic Cloud] takes place in the majority of cases—over 93 percent,” Cautun says.

The collision would be a slow showdown, unfolding over the course of billions of years. Stars from the Large Magellanic Cloud would ricochet like pinballs, dislodging some of the Milky Way’s stars from their orbits. Our galaxy as a whole would survive, but some stars may be flung right out of the Milky Way, Cautun says.

Read: The Milky Way is still feeling the effects of an ancient encounter

Meanwhile, the sleeping, supermassive black hole at the center of the Milky Way would wake up. Like volcanoes, black holes alternate between peaceful dormancy and ferocious activity, depending on the surrounding conditions. Ours is in a quiet period. But the chaos of the merger would send cosmic gas swirling toward it, and cosmic gas is dinner to black holes. The resulting feast is a spectacular show. A disk of luminous, hot cosmic material swirls around the black hole at great speed, and bursts of high-energy radiation erupt from its center. Cautun says one serving of a Large Magellanic Cloud could lead our black hole to gobble up enough material to grow 10 times its current size.



And what would happen to us, if there is any kind of “us”—life in some form—on Earth when this all goes down?

It is possible that our sun could be among the small fraction of stars that gets lobbed from the galaxy. The jostling would disturb the orbits of our solar system’s planets, which could be perilous for any inhabitants. Even a small change in the relationship between the sun and the Earth could knock it out of the region where liquid water (and, therefore, life) can exist.

If life on Earth survived, though, it would take ages for anyone to realize the planet’s position in the cosmos has shifted. Like the merger, the solar system’s ejection would occur over such a large timescale that it’d be almost meaningless to humans. “Only at the end of the collision could our descendants tell if we have been kicked out of our galaxy,” Cautun says.

The change in scenery would be remarkable. In this scenario, “our descendants will see a very different night sky, much darker than currently, with only a modest bright patch that will correspond to the Milky Way galaxy,” Cautun says. “It will be tremendously more difficult for our descendants to travel to other stars—if they haven’t yet done so by that time.”

If this imagined future scares you, consider that a collision with Andromeda would be much worse. The Milky Way would easily devour the smaller Large Magellanic Cloud and maintain its signature spiral shape, even if its insides will be all jumbled. Andromeda, on the other hand, is about the same size as the Milky Way. Astronomers expect that mashup to be destructive, and the Milky Way as we know it—the neat, shimmering band of stars—is unlikely to survive.

Cautun says that a collision between the Milky Way and the Large Magellanic Cloud would shift our galaxy’s position in space. But Andromeda will still come for it, a few billion years later.

“Ultimately, there is no escape,” he says.