Magnetic 'Force Field' May Save Giant Gas Cloud During Milky Way Collision

A gigantic streamer of hydrogen gas, called the Smith Cloud, is on a collision course for the Milky Way. Now, though, it seems that this cloud's seemingly inevitable doom may be avoided. Scientists have discovered a magnetic field deep in the cloud's interior, which may protect it during its meteoric plunge into the disk of our galaxy.

Currently, the Smith Cloud is hurtling toward the Milky Way at an astonishing 150 miles per second. Known as a high velocity cloud (HVC), the Smith Cloud is predicted to hit in about 30 million years. When it does, it will set off a spectacular burst of star formation--assuming it survives careening through the halo of hot ionized gas surrounding the Milky Way.

"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, one of the researchers, in a news release. "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 the plunge."

The Smith Cloud appears to have already survived a similar plunge in the past. Earlier research reveals that this cloud may have punched through the disk of our galaxy once at about 8,000 light-years from the disk.

Millions of these HVCs zip around our galaxy. Yet their orbits seldom correspond to the rotation of the Milky Way. It's very possible that HVCs are the left-over building blocks of galaxy formation or the splattered remains of a close galactic encounter billions of years ago. The Smith Cloud, in particular, may possess an internal magnetic field. Yet scientists have yet to confirm their findings.

"The field we observe now is too large to have existed in its current state when the cloud was formed," said Hill. "The field was probably magnified by the cloud's motion through the halo."

The findings reveal a little bit more about our galaxy and how it interacts with the surrounding environment. More specifically, it shows what might happen in the future when it comes to the Smith Cloud. A bright ring of stars may be produced after the collision, though present day astronomers won't be around to see it.

The findings are published in The Astrophysical Journal.