  We report the discovery of the first new ultra-cool brown dwarf found with
the Wide-field Infrared Survey Explorer (WISE). The object's preliminary
designation is WISEPC J045853.90+643451.9. Follow-up spectroscopy with the
LUCIFER instrument on the Large Binocular Telescope indicates that it is a very
late-type T dwarf with a spectral type approximately equal to T9. Fits to an
IRTF/SpeX 0.8-2.5 micron spectrum to the model atmospheres of Marley and Saumon
indicate an effective temperature of approximately 600 K as well as the
presence of vertical mixing in its atmosphere. The new brown dwarf is easily
detected by WISE, with a signal-to-noise ratio of ~36 at 4.6 microns. Current
estimates place it at a distance of 6 to 10 pc. This object represents the
first in what will likely be hundreds of nearby brown dwarfs found by WISE that
will be suitable for follow up observations, including those with the James
Webb Space Telescope. One of the two primary scientific goals of the WISE
mission is to find the coolest, closest stars to our Sun; the discovery of this
new brown dwarf proves that WISE is capable of fulfilling this objective.
