FYI.

This story is over 5 years old.

Tech

Astronomers Found the First Evidence of Water Clouds Beyond Our Solar System

The weather forecast on a nearby brown dwarf is partly cloudy, with some freaky ice storms.
Artist's impression of a brown dwarf. Image: NASA/JPL-Caltech

The first evidence of water-ice clouds on a world outside our solar system has been discovered, according to a study published today in the Astrophysical Journal Letters. Though water vapor has been detectedon extrasolar planets before, this is the only instance in which full clouds have been scoped out by astronomers.

This icy cloud world is a brown dwarf star formally known as WISE J085510.83-071442.5, but it goes by W0855 for short. It was only discovered a few months ago, by Penn State's Kevin Luhman, a seasoned brown dwarf hunter. These weird failed stars are very difficult to root out because they never learned how to undergo nuclear fusion, and thus don't produce starlight.

Advertisement

Indeed, at only 7.2 light years distant, W0855 is actually the fourth closest star to the Sun, but it's so dim that it's invisible in any wavelength shorter than infrared (excepting the occasional X-ray belch).

But W0855 is an odd duck even for this nebulous category. It is by far the coldest star ever found, wavering up to around only nine degrees Fahrenheit. No sooner was this freezing world discovered than astronomers were eager to see if it would provide the first evidence of water ice clouds outside of our solar system.

"The conditions had to be near-perfect from the ground in order for the detection to work," lead author Jacqueline Faherty told me. "I needed clear, calm skies and everything had to work perfectly with the instrument."

Luckily, it did. Faherty used the FourStar near-infrared camera at the Las Campanas Observatory to image the brown dwarf. She and her team captured 50 images their first night, 61 on the second, and 40 on the third. Spectral analysis provided significant evidence that W0855 is shrouded with atmospheric water ice, and also suggested a hefty dose of sulfide cloud cover.

According to the study, W0855 could be a very useful "gateway object" for studying extrasolar gas giants of similar temperatures, atmospheric conditions, and sizes. Our own solar system's gas giants have water ice clouds too, but they're masked by layers of ammonia and other atmospheric material. Our brown dwarf neighbor presents a unique glimpse at what a water-rich planet might look like, and perhaps, how to find these worlds.

Along those lines, Faherty and her team are eager to use the James Webb Space Telescope, scheduled for launch in 2018, to get a closer look at its behavior. W0855 is interesting on its own merits, but it could also provide a road map to finding water on exoplanets.

"These are indications of water clouds," Faherty said. "The next step is to get a spectrum of the object to confirm that water molecules are present. Modelers predict that water ice clouds should be an important opacity source for extrasolar planets."

"This object is not considered a planet, but is analogous," she continued. "It's a glimpse into what we will find with future missions that want to characterize the diverse atmospheres found on planets around other stars."