Monstrous Gas Cloud is Hurtling Toward Our Milky Way Galaxy

A massive cloud has actually boomeranged back to our galaxy. Scientists have found that an immense cloud of hydrogen gas outside the Milky Way galaxy is plummeting toward us at nearly 700,000 miles per hour.

Hundreds of enormous, high-velocity clouds whiz around the outskirts of our galaxy. However, the "Smith Cloud" is unique since its trajectory is well known. New Hubble observations suggest it was actually launched from the outer regions of the galactic disk about 70 million years ago.

Now, the cloud is on a return collision course and is expected to plow into the Milky Way's disk in about 30 million years. When it does, astronomers believe that it will ignite a spectacular burst of star formation, perhaps providing enough gas to make 2 million suns.

"The cloud is an example of how the galaxy is changing with time," said Andrew Fox, one of the researchers, in a news release. "It's telling us that the Milky Way is a bubbling, very active place where gas can be thrown out of one part of the disk and then return back down into another. Our galaxy is recycling its gas through clouds, the Smith Cloud being one example, and will form stars in different places than before. Hubble's measurements of the Smith Cloud are helping us to visualize how active the disks of galaxies are."

Astronomers have measured this comet-shaped region of gas to be 11,000 light-years long and 2,500 light-years across. If the cloud could be seen in visible light, it would span the sky with a diameter that was 30 times greater than the size of a full moon.

The researchers found that the Smith Cloud is also as rich in sulfur as the Milky Way's outer disk, which is a region about 40,000 light-years from the galaxy's center. This means that the Smith Cloud was enriched by materials from stars.

The findings reveal a bit more about the Smith Cloud's origins. With that said, the researchers are now curious how the cloud got to where it is now.

The findings are published in The Astrophysical Journal.

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