Washington, D.C.—A team of scientists led by Carnegie's Jacqueline Faherty
has discovered the first evidence of water ice clouds on an object
outside of our own Solar System. 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. Their findings
are published today by The Astrophysical Journal Letters and are available here.
At the Las Campanas Observatory in Chile, Faherty, along with a team
including Carnegie's Andrew Monson, used the FourStar near infrared
camera to detect the coldest brown dwarf ever characterized. Their
findings are the result of 151 images taken over three nights and
combined. The object, named WISE J085510.83-071442.5, or 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.
Chris Tinney, an Astronomer at the Australian Centre for
Astrobiology, UNSW Australia and 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 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 neighbor 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 paper's other co-author is Andrew Skemer of the University of Arizona.
* * * * *
This work was supported by the Australian Research Council. It made
use of data from the NASA WISE mission, which was a joint project of the
University of California Los Angeles and the Jet Propulsion Laboratory
and Caltech, funded by NASA. It also made use of the NASA/IPAC Infrared
Science Archive, which is operated by the Jet Propulsion Laboratory and
Caltech, under contract with NASA.
Source: Carnegie Institution for Science
