ATLAS lifts the Cup: Discovery of a New Milky Way satellite in Crater
  We announce the discovery of a new Galactic companion found in data from the
ESO VST ATLAS survey, and followed up with deep imaging on the 4m William
Herschel Telescope. The satellite is located in the constellation of Crater
(the Cup) at a distance of $\sim$ 170 kpc. Its half-light radius is $r_h=30$ pc
and its luminosity is $M_V=-5.5$. The bulk of its stellar population is old and
metal-poor. We would probably have classified the newly discovered satellite as
an extended globular cluster were it not for the presence of a handful of Blue
Loop stars and a sparsely populated Red Clump. The existence of the core helium
burning population implies that star-formation occurred in Crater perhaps as
recently as 400 Myr ago. No globular cluster has ever accomplished the feat of
prolonging its star-formation by several Gyrs. Therefore, if our hypothesis
that the blue bright stars in Crater are Blue Loop giants is correct, the new
satellite should be classified as a dwarf galaxy with unusual properties. Note
that only ten degrees to the North of Crater, two ultra-faint galaxies Leo IV
and V orbit the Galaxy at approximately the same distance. This hints that all
three satellites may once have been closely associated before falling together
into the Milky Way halo.
