Massive Cloud to Strike Milky Way, Scientists Say

January 14, 2008

An incoming cloud of hydrogen gas will likely trigger a huge burst of star formation—and then numerous violent supernovae—when it collides with the Milky Way in less than 40 million years, scientists say.

That's the prediction of Jay Lockman, of the National Radio Astronomy Observatory, and a team of astronomers that studied the cloud's radio signals.

The enormous cloud, known as Smith's Cloud, contains enough hydrogen to make a million suns.

The cloud is currently about 8,000 light-years from the Milky Way's disk and about 40,000 light-years from Earth. It is approaching at 150 miles (240 kilometers) a second, poised to strike the Milky Way's disk at an angle of about 45 degrees.

The scientists predict that as the cloud's full bulk makes contact, the impact will spawn a region of hot, new stars that could quickly burst as supernovae, devastating any habitable planets in the vicinity.

Everywhere else—such as Earth, well beyond the region of danger—will get a good show, Lockman said.

"Over a few million years, it will look like a celestial New Year's celebration, with huge firecrackers going off in that region of the galaxy."

(Related: "Brightest Known Supernova Detected" [October 15, 2007].)

The findings were presented Friday during a meeting of the American Astronomical Society in Austin, Texas.

Orion-Size Cloud

Graduate student Gail Smith found the cloud in 1963.

Astronomers don't know for sure whether it was originally part of the Milky Way or something just arriving in the area. (Get a Milky Way wallpaper.)

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