The Planet Killer from Star Trek Episode #35
“The Doomsday Machine”

Science fiction gets another chance to get it all wrong.

A study using the Canada-France-Hawaii telescope based in Hawaii confirmed that as the Andromeda galaxy moves through our local cosmic neighborhood, it eats everything in its path—including, eventually, us.

Andromeda grows by pulling galactic companions to it, like spare change down a sewer grate. The astronomers found evidence of this interaction by detecting stars streaming off some dwarf galaxies not fully absorbed by Andromeda. The shape of these streams traces the size and history of the galaxies being pulled in, says MIT astrophysicist Robert Simcoe, and is determined by the mass of the galaxy itself: the larger the galaxy being eaten, the closer the stream will be to its center.

So will Andromeda tear our galaxy apart as it devours us? Not exactly, says Pauline Barmby, one of the study’s authors. While it’s easy to picture stars zooming toward Earth like a cataclysmic meteor shower, says Barmby, “an important thing to know is that the stars and galaxies are actually very far apart.” When Andromeda and the Milky Way do come together, there will still be tens of thousands of light years between their stars. To quote Billy Bob Thornton from the film Armageddon, “It’s a big ass sky.”

If galaxies are consumed, continues Barmby, “nothing happens to the stars themselves. They get moved around, they can get stretched out into these tidal tails and things, but nothing happens to them.” For example, if life on Earth coincided with Andromeda absorbing our galaxy, we would hardly notice it.

“It’s actually a slow, stately event,” says Barmby.

So much for the next big sci fi flick.