Brown dwarf may contain first known extrasolar water clouds

Science : Although some extrasolar objects have been found to have water vapor in their atmospheres, a brown dwarf just 7.3 light-years from Earth appears to be the first to have clouds made of water. Labeled WISE J0855-0714, the object was initially found in images collected by NASA’s Wide-Field Infrared Survey Explorer (WISE) between 2010 and 2011. Brown dwarfs are star-like objects whose masses are too low to sustain hydrogen fusion and too high to qualify the objects as gas giant planets. The cloudy brown dwarf is the fourth closest star system to Earth. It is Jupiter-sized but 3–10 times as massive and is the coldest known brown dwarf, with a temperature slightly colder than Earth’s average temperature but warmer than Jupiter’s. Jacqueline Faherty of the Carnegie Institution of Washington and her colleagues created a composite of the object from 151 near-IR images taken by the Magellan Baade telescope in Chile. The composite image revealed a pattern of colors that matched a model of brown dwarfs that contain clouds of water ice and of sodium sulfide.