There’s a big cloud heading toward us, but it’s not the kind that looks like an elephant or your Uncle Todd. NASA’s Hubble Space Telescope has been tracking the so-called Smith Cloud, which is charging toward the Milky Way at some 700,000 miles per hour. Made up largely of hydrogen gas, the Smith Cloud can’t be seen by the naked eye, but it can be detected with radio waves. Of all the gaseous clouds floating around in space (and there are a lot of them), this is perhaps the most famous and possibly even the most beloved, as its path toward our galaxy has been well-documented since its initial discovery in the 1960s.

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Earlier this year, NASA reported that the Smith Cloud began its journey toward the Milky Way around 70 million years ago, a conclusion scientists based on new data obtained by the Hubble telescope. The Smith Cloud, like others on the outskirts of our galaxy, contains the amount and types of gas plus heavy metals that suggest it could wind up producing millions of new stars. NASA data estimates the cloud, which has a comet-like shape, is “11,000 light-years long and 2,500 light-years across,” according to an earlier report. “If the cloud could be seen in visible light, it would span the sky with an apparent diameter 30 times greater than the size of the full moon.”

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Essentially, the Smith Cloud is getting whipped back into the outer edge of the Milky Way. It could be 30 millions years before the giant cloud of hydrogen gas meets the edge of our galaxy, but in the meantime, NASA scientists are working to learn more about its composition, which would offer new clues about its origin. So far, they’ve learned the cloud is as rich in sulfur as the Milky Way’s outer disk, a region about 40,000 light-years from the galaxy’s center. That discovery indicates Smith Cloud was enriched by star material, leading scientists to believe it may have been hurled out of our galaxy at some point, rather than having its origins in a separate failed galaxy.

What caused the hydrogen cloud to be ejected from the Milky Way is anyone’s guess, and NASA researchers are continuing to study the data and perform other tests to unlock more secrets hidden within this mysterious, invisible cloud.

Via ABC7 and NASA

Images via NASA