Space Cloud on Collision Course

A cloud of hydrogen 11,000 light years long and 2500 light years wide is headed straight for our galaxy, and the inevitable collision will create a spectacular burst of star formation. But don't plan your viewing party yet—Smith's Cloud, as it is called, won't arrive for another 20 to 40 million years, Space.com reports.

The cloud, discovered in 1963, is thought to contain enough hydrogen to make a million sun-like stars. It is moving toward the Milky Way at 540,000mph and will hit far from our solar system. To see Smith's Cloud you'd need a radio telescope, which scientists used to determine whether it was approaching or leaving our galaxy. (More Milky Way stories.)