The massive Smith Cloud of hydrogen gas is on a collision course with the Milky Way galaxy, and while galaxy's outer layer of hot ionized gas destroys most gas clouds, scientists have discovered the Smith Cloud has a special line of defense: a "magnetic force field."
"The million-degree upper atmosphere of the galaxy ought to destroy these hydrogen clouds before they ever reach the disk, where most stars are formed," said Alex Hill, an astronomer at Australia's Commonwealth Scientific and Industrial Research Organization. "New observations reveal one of these clouds in the process of being shredded, but a protective magnetic field shields the cloud and may help it survive its plunge."
The Smith Cloud is currently 8,000 light-years from the Milky Way and zooming toward the galaxy at more than 150 miles per second. The two are set to collide in 30 million years. Gas clouds such as the Smith Cloud contain vital ingredients for star formation and the collision should spark the formation of many new stars.
The Smith Cloud's arrival won't be the first time it will enter the Milky Way. The high-velocity cloud is believed to have already passed through the galaxy one time before, and the recently-discovered magnetic field within the cloud's interior explains how it's able to continue careening around.
"The Smith Cloud is unique among high-velocity clouds because it is so clearly interacting with and merging with the Milky Way," said Felix J. Lockman, an astronomer at the National Radio Astronomy Observatory. "Its comet-like appearance indicates it's already feeling the Milky Way's influence."
You can read the full published study detailing the findings in The Astrophysical Journal.
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