Hubble's Star

Etymology
. From having the variable nature of this star being discovered by. From this being a very important star in the history of astronomy, and the discovery made using it by Hubble, that the Universe contains galaxies beyond the Milky Way, and is much larger than just the size of the Milky Way Galaxy.

Proper noun

 * : ; the first variable star discovered outside the Milky Way Galaxy, and first star identified whose distance was unequivocably beyond the confines of the Milky Way.