Astronomers led by Dr Jacqueline Faherty from Carnegie Institution of Washington and American Museum of Natural History have discovered evidence of water ice clouds floating in the atmosphere of what is the coldest known brown dwarf, WISE J085510.83-071442.5 (W0855 for short).
This artist’s conception shows W0855, the coldest known brown dwarf. Image credit: NASA / JPL-Caltech / Penn State University.
Brown dwarfs aren’t quite very small stars, but they aren’t quite giant planets either. They are too small to sustain the hydrogen fusion process that fuels stars.
Their temperatures can range from nearly as hot as a star to as cool as a planet, and their masses also range between star-like and giant planet-like.
They are of particular interest to scientists because they offer clues to star-formation processes. They also overlap with the temperatures of planets, but are much easier to study since they are commonly found in isolation.
Located about 7.2 light-years away, the brown dwarf W0855 is the fourth-closest system to our own Sun, after Alpha Centauri AB – Proxima Centauri, Barnard’s Star and WISE 1049-5319.
Dr Faherty’s team detected the frozen clouds of sulfide and water in the W0855’s atmosphere by comparing near-infrared images of the object models for predicting the atmospheric content of brown dwarfs.
Water ice clouds exist on our own gas giant planets – Jupiter, Saturn, Uranus, and Neptune – but have not been seen outside of the Solar System until now.
“Ice clouds are predicted to be very important in the atmospheres of planets beyond our Solar System, but they’ve never been observed outside of it before now,” said Dr Faherty, who is the lead author of a paper published in the Astrophysical Journal Letters (arXiv.org pre-print).
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Jacqueline K. Faherty et al. 2014. Indications of Water Clouds in the Coldest Known Brown Dwarf. ApJ 793, L16; doi: 10.1088/2041-8205/793/1/L16
