Found: First evidence for water ice clouds outside Solar System

The first tell-tale signs of water ice clouds on an object outside our Solar System may have been discovered

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An artist's impression of brown dwarf W0855, which rests around seven light years away

An artist’s impression of brown dwarf W0855, which rests around seven light years away

For the first time, astronomers believe that they may have found the tell-tale signs of water ice clouds on an object outside our Solar System.

“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,” explains Jacqueline Faherty of the Carnegie Institution for Science, who led the study.

The celestial body, referred to as W0855 and of which holds the tantalising evidence, is a brown dwarf. These objects are too small to be lumped into the star category, but they aren’t quite big enough to be planets either. It’s said that brown dwarfs aren’t able to sustain the hydrogen fusion process that power stars, yet their temperatures can range from as nearly hot as a star to as cool as a planet.

W0855 isn’t new to scientists. It was first spotted by NASA’s Wide-Field Infrared Explorer mission and holds the record for the coldest brown dwarf ever characterised with a temperature somewhere between -48 to -13 degrees Celsius (-55 to 8 degrees Fahrenheit). At a distance of seven light years away, this object is practically a next-door neighbour to our Sun. However, despite its proximity, astronomers weren’t certain if they could pick it up using Earth-based telescopes.

The size of a brown dwarf in comparison to our Sun, a low mass star, Jupiter and Earth

The size of a brown dwarf in comparison to our Sun, a low mass star, Jupiter and Earth

“This was a battle at the telescope to get a detection,” admits Faherty, who employed the FourStar near-infrared camera at the Las Campanas Observatory in Chile to obtain 151 images taken over three nights, which were then combined. It was here that she and her team found evidence for frozen clouds of sulphide and water.

“This a great result. This object is so faint and it’s exciting to be the first people to detect it with a telescope on the ground,” adds Chris Tinney, an astronomer at the Australian Centre for Astrobiology at UNSW Australia, and co-author of a paper published in The Astrophysical Journal Letters.

We know that clouds laden with water ice exist in the confines of our Solar System on giant planets Jupiter, Saturn, Uranus and Neptune. However, this is the furthest from our Sun that we’ve been able to detect water-based clouds up until now.

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