Sky & Telescope - August 10, 2007
The infrared deep-sky survey now being carried out by the United Kingdom Infrared Telescope is only 5% done, but already astronomers looking at its data have found the coolest solitary brown dwarf ever seen.
The object, named ULAS J0034–00, is located in Cetus. A followup analysis by the Gemini Observatory of steam and methane features in its infrared spectrum pegs its temperature at just 600 to 700 kelvins (330° to 430°C, or 620° to 800°F). This puts it at the very bottom of spectral class T — or perhaps in the still-cooler proposed spectral class Y, for which no other object has yet been found. ...