The spectrum not only confirms, with “the best evidence,” that objects that cold would have water clouds but also provides new insight into this outer star as well as into Jupiter, Andrew Skemer, assistant professor of astronomy and astrophysics at UC Santa Cruz, said in a press release this week.
“Our spectrum shows that WISE 0855 is dominated by water vapor and clouds, with an overall appearance that is strikingly similar to Jupiter,” Skemer, who co-authored the report, said. “Now that we have a spectrum, we can really start thinking about what’s going on in this object.”
In addition to abundant water vapor, Jupiter and WISE 0855 also share similar temperatures — WISE 0855 being around 250 Kelvin or -9 degrees Fahrenheit, and Jupiter at 130 Kelvin.
“WISE 0855 is our first opportunity to study an extrasolar planetary-mass object that is nearly as cold as our own gas giants,” Skemer said.
The brown dwarf likely has a less turbulent atmosphere than Jupiter, however. That’s because it does not heavily absorb the toxic gas phosphine like Jupiter does, the report explains. It’s also about five times the mass of Jupiter.
“The spectrum allows us to investigate dynamical and chemical properties that have long been studied in Jupiter’s atmosphere, but this time on an extrasolar world,” Skemer noted.
The atmospheric findings appear to further blur the line between planets and brown dwarfs, which are often called “failed stars.”
That’s because they are smaller than typical stars, though larger than planets, and therefore unable to sustain the nuclear fusion that makes regular stars shine, NASA explains on its website.