A cloudy day here on Earth might be a sign for gloom, but elsewhere in the universe, to behold one is a scientific achievement. In this case, a team of researchers from UC Santa Cruz announced that they have detected water clouds for the first time outside our solar system on a brown dwarf known as WISE 0855, which is around 7.2 light-years away from Earth.
WISE 0855 is probably not actually blue, but here's an artist's impression of it. Image: NASA/JPL-Caltech/Penn State University.
The study was published back in May in Astrophysical Journal Letters by a team from UC Santa Cruz and NASA and updates what we currently know about the dwarf, which was discovered in 2014 by NASA's Wide-field Infrared Survey Explorer (WISE). Scientists had detected tentative water clouds back in the original study, but had limited photometric data and needed a deeper infrared image to confirm.
Using the Gemini North telescope in Hawaii, they were able to use spectroscopy to gather more information. Researchers confirmed that the dwarf's atmosphere is "dominated by water vapour and clouds."
"It's five times fainter than any other object detected with ground-based spectroscopy at this wavelength," co-author and assistant professor of astronomy and astrophysics at UC Santa Cruz Andrew Skemer said. "Now that we have a spectrum, we can really start thinking about what's going on in this object."
In regards to planets in our solar system, WISE 0855 is closest in composition to Jupiter, although it's much larger — five times larger in fact. It's considered a "failed star" or a "brown dwarf" because it was formed in the same way as stars, but wasn't large enough to ignite the nuclear fusion reactions required to make a star.
Its average temperature is about 250 Kelvin, or -23°C, making it nearly as cold as Jupiter, which clocks in at around 130 Kelvin.
WISE 0855 and Jupiter are also both similar in water absorption features, but researchers noted that Jupiter has an abundance of phosphine in its atmosphere, meaning it has a more turbulent atmosphere. WISE 0855 doesn't.
Researchers hope to use WISE to uncover more brown dwarfs that will allow them to study the chemical properties in Jupiter's atmosphere, but on another body. With these results, they also hope to better understand the nature of clouds on objects besides Earth and the atmospheres of colder planets.