Astronomers Discover 11 Runaway Galaxies Flung from Their Homes

Astronomers have spotted 11 runaway galaxies that have been flung from their original homes to wander through space. The new findings reveal a bit more about these strange and unusual features.

An object is known as a "runaway" if it's moving faster than escape velocity. This means that, essentially, the object will leave its home, never to return. In the case of a runaway star, as an example, that speed is more than a million miles per hour. A runaway galaxy, in contrast, has to go even faster: about 6 million miles per hour.

When the researchers first began their hunt, they initially set out to identify new members of a class of galaxies called compact ellipticals. These tiny blobs of stars are bigger than star clusters, but smaller than a typical galaxy. In fact, they span only a few hundred light-years. In comparison, the Milky Way is 100,000 light-years across.

In all, the scientists identified about 200 previously unknown compact galaxies. More interesting, though, was that 11 of these were completely isolated and found far from any large galaxy or galaxy cluster. But what could create these lonesome galaxies in the first place?

The scientists believe that the answer is a classic three-body interaction. A compact elliptical could be paired with a large galaxy that stripped it of its stars. Then a third galaxy could interrupt the two and fling the compact elliptical away. The larger galaxy would then absorb the third galaxy.

The findings reveal a bit more about these compact galaxy and explain what may cause them to wander so far from home. It turns out that it may be the interaction of titans: galaxies that interrupt and crash into one another.

The findings are published in the journal Science.

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