Scientists have discovered the first evidence of water ice clouds on an object outside of our own solar system, about 7.3 light-years away from Earth.
Water ice clouds exist on our own gas giant planets - Jupiter, Saturn, Uranus, and Neptune - but have not been seen outside of the planets orbiting our Sun until now.
The team led by Jacqueline Faherty of the Carnegie Institution for Science in Washington used a near infrared camera at the Las Campanas Observatory in Chile to detect the coldest brown dwarf ever characterised.
Their findings are the result of 151 images taken over three nights and combined.
The object, named W0855, was first seen by NASA's Wide-Field Infrared Explorer mission and published earlier this year. But it was not known if it could be detected by Earth-based facilities.
"This was a battle at the telescope to get the detection," said Faherty.
"This is 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," Chris Tinney, an Astronomer at the Australian Centre for Astrobiology, University of New South Wales (UNSW) Australia and co-author on the result said.
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.
W0855 is the fourth-closest system to our own Sun, practically a next-door neighbour in astronomical distances.
A comparison of the team's near-infrared images of W0855 with models for predicting the atmospheric content of brown dwarfs showed evidence of frozen clouds of sulfide and water.
"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," Faherty said.
The findings were published in The Astrophysical Journal Letters.
