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Giant hydrogen cloud headed for Milky Way

Gaseous interloper could deliver extragalactic material to galaxy upon collision

5:28pm, February 15, 2015
Smith Cloud

GOING STREAKING  The Smith Cloud, a massive smear of hydrogen, is shooting toward the Milky Way and is set to collide with the galaxy in 27 million years. It could deliver fresh extragalactic material, new data suggest.

SAN JOSE, Calif. — A high-speed hydrogen cloud on a crash course with the Milky Way appears to be an exotic interloper, preliminary data suggest.

The cometlike streak, called the Smith Cloud, is as massive as a million suns and is shooting toward the galaxy at roughly 850,000 kilometers per hour. At about 40,000 light-years away, the cloud is on schedule to collide with the one of the galaxy’s spiral arms in roughly 30 million years. When it does, it could deliver extragalactic material to the Milky Way, said astronomer Jay Lockman of the National Radio Astronomy Observatory.

Lockman and his colleagues used the Green Bank Telescope in West Virginia to compare the Smith Cloud with others near the galaxy and seven massive ones that sit between the Andromeda and Triangulum galaxies. Smith’s Cloud is more similar to the ones that sit far-off, which suggests that the cloud originated

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