Milky Way Shreds Dwarf Galaxy Into Four Star Streams

As a dwarf galaxy, in this case Sagittarius, falls into bigger galaxies (Milky Way), it has been known that tails of stars are pulled out of the dwarf by gargantuan tidal force. Astronomers have discovered 4 such streams emanating from Sagittarius.
credit : S. Koposov and the SDSS-III collaboration