An article published in “The Astrophysical Journal Letters” describes a research about the so-called “”Smith Cloud” (or “Smith’s Cloud”). It’s a giant cloud of hydrogen which is currently outside of the Milky Way but is heading towards our galaxy at about 1.1 million km/h (almost 700,000 mph). Observations made using the Hubble Space Telescope suggest that it was ejected from the Milky Way galaxy about 70 million years ago and now is coming back.