  Through a previous analysis of multi-epoch astrometry from the Wide-field
Infrared Survey Explorer (WISE), I identified WISE J085510.83-071442.5 as a new
high proper motion object. By combining astrometry from WISE and the Spitzer
Space Telescope, I have measured a proper motion of 8.1+/-0.1"/yr and a
parallax of 0.454+/-0.045" (2.20+0.24/-0.20 pc) for WISE J085510.83-071442.5,
giving it the third highest proper motion and the fourth largest parallax of
any known star or brown dwarf. It is also the coldest known brown dwarf based
on its absolute magnitude at 4.5um and its color in [3.6]-[4.5]. By comparing
M4.5 with the values predicted by theoretical evolutionary models, I estimate
an effective temperature of 225-260 K and a mass of 3-10 Mjup for the age range
of 1-10 Gyr that encompasses most nearby stars.
