Galactic Threesomes Scared Some Systems Into Going Rogue

If you've ever seen the movie "Get Him to the Greek," featuring comedians Russell Brand and Jonah Hill, you probably now understand that threesomes can be weird. They can even be downright scary! That's why it came as no surprise when astronomers determined that when galaxies have a threesome, entire systems might run for it.

That's at least according to a study recently published in the journal Science, which details how there are what appear to be dozens-of-billions of near-undetectable, free-floating planets straggling around the edge of our Milky Way Galaxy. Further investigation revealed that these 'rogues' are not alone. There are about two dozen known stars that escaped from our galaxy at high velocities, and even one runaway star cluster hosting a million stars that fled the giant galaxy Messier87 in the Virgo cluster.

So what the heck is causing this? One suspicion is that it's the result of intense galactic collisions within an existing cluster - a theory that was bolstered by the discovery of numerous compact elliptical galaxies floating around much larger neighbors. These little guys are so small that they look like the stripped cores of older ordinary galaxies - the losers of duals of galactic proportions.

Then in 2013, the first compact elliptical was found far away from any massive galaxy, so that it became unclear where it came from. Soon after, 200 additional tiny galaxies were discovered floating aimlessly in space - millions of light-years from the nearest galaxy cluster.

"We asked ourselves, how we could explain them?" Igor Chilingarian, who authored the Science paper, explained in a statement.

After determining that these rogue ellipticals boast the same unusual properties of those defeated galaxies found still within clusters, Chilingarian and his colleagues now believe they have an answer.

While a clash between only two galaxies can result in one being stripped down to its bones, the smallest galaxy in a violent galactic threesome can be violently thrown by the ongoing battle of the two that remain.

To support this theory, the astronomers even analyzed the velocity spread of compact ellipticals in nearby galaxy clusters, finding that some of them are on the verge of escaping their host clusters at speeds approaching approximately 2500 km/s (~1550 mi/s).

"These small galaxies face a lonely future, exiled from galaxy clusters they were formed and used to live in," Chilingarian added.

But at least they can 'live' on. Astronomers have long known that the smaller survivor that remains nearby following a galactic dual is often later devoured by the dominant system.

Still, it serves as a lesson learned concerning threesomes. It's all fun and games until a friendly neighbor is thrown billions of light-years away.

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