We announce the discovery of a new Milky Way satellite Segue 2 found in the data of Sloan Extension for Galactic Understanding and Exploration ( SEGUE ) .
We followed this up with deeper imaging and spectroscopy on the Multiple Mirror Telescope ( MMT ) .
From this , we derive a luminosity of M _ { v } = -2.5 , a half-light radius of 34 pc and a systemic velocity of \sim - 40 kms ^ { -1 } .
Our data also provides evidence for a stream around Segue 2 at a similar heliocentric velocity , and the SEGUE data show that it is also present in neighbouring fields .
We resolve the velocity dispersion of Segue 2 as 3.4 kms ^ { -1 } and the possible stream as \sim 7 kms ^ { -1 } .
This object shows points of comparison with other recent discoveries , Segue 1 , Boo II and Coma .
We speculate that all four objects may be representatives of a population of satellites of satellites – survivors of accretion events that destroyed their larger but less dense parents .
They are likely to have formed at redshifts z > 10 and are good candidates for fossils of the reionization epoch .