Monstrous “Smith Cloud” boomerangs back to the Milky Way

New Hubble observations suggest that an immense cloud of hydrogen gas was launched from the outer regions of the galactic disc around 70 million years ago and is plummeting back toward our galaxy at nearly 700,000 miles per hour. If this so-called “Smith 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.