16th September 2014 First evidence of water ice clouds beyond our Astronomers have discovered the first evidence of water ice clouds on an object outside our own Solar System.
Scientists at the Carnegie Institution of Washington report the first evidence of water ice clouds on a body outside of our own Solar System. Water ice clouds are present on the gas giants – Jupiter, Saturn, Uranus, and Neptune – but have never been seen outside the planets orbiting our Sun until now. This finding is published by The Astrophysical Journal Letters. At the Las Campanas Observatory in Chile, a near-infrared camera was used to detect WISE 0855–0714 (also called W0855) a tiny sub-brown dwarf located approximately 7.3 light years from Earth. This was first seen by a NASA space telescope – Wide-Field Infrared Survey Explorer – and confirmed in April 2014. But it was not known if the object could be seen by ground-based facilities. The Carnegie researchers managed to obtain 151 images from Las Campanas over a period of three nights. "This was a battle at the telescope to get the detection," said Jacqueline Faherty, who led the study. Chris Tinney, co-author on the result, stated: "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."
Brown dwarfs are too small to be classified as stars, but too large to be considered planets. Because of their size, 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, practically next door in terms of astronomical distances. It is also the coldest object of its type found in interstellar space, having a temperature between 225 to 260 K (−48 to −13°C; −55 to 8°F). A comparison of 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 next generation of telescopes – such as the E-ELT (2022), PLATO observatory (2024-2030) and the ATLAST project (2025-2035) – will provide more detailed views of planets' and brown dwarfs' atmospheres.
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