like an emerald necklace . This is one of the coolest brown dwarfs known, with a temperature of roughly 600 Kelvin , or 620 degrees Fahrenheit . Photo credit: NASA/JPL-Caltech/UCLA Share | Posted by JDsg at 11/11/2010 12:00:00 AM Labels: Brown Dwarf Stars , Infrared astronomy , WISE , WISEPC J045853.90+643451.9