Free Astronomy Magazine March-April 2024

22 MARCH-APRIL 2024 ASTRO PUBLISHING down into our atmosphere along magnetic field lines near Earth’s poles, colliding with gas molecules and creating eerie, dancing curtains of light. Jupiter and Saturn have similar auroral processes that in- volve interacting with the solar wind, but they also get auroral con- tributions from nearby active moons like Io (for Jupiter) and Enceladus (for Saturn). For isolated brown dwarfs like W1935, the absence of a stellar wind to contribute to the au- roral process and explain the extra energy in the upper atmosphere re- quired for the methane emission is a mystery. The team surmises that either unac- counted internal processes like the atmospheric phenomena of Jupiter and Saturn, or external interactions with either interstellar plasma or a nearby active moon may help ac- count for the emission. The aurorae’s discovery played out like a detective story. A team led by Jackie Faherty, an astronomer at the by NASA/ESA/CSA − Christine Pulliam A stronomers using NASA’s James Webb Space Tele- scope have found a brown dwarf (an object more massive than Jupiter but smaller than a star) with infrared emission from methane, likely due to energy in its upper at- mosphere. This is an unexpected discovery because the brown dwarf, W1935, is cold and lacks a host star; therefore, there is no obvious source for the upper atmosphere energy. The team speculates that the methane emission may be due to processes generating aurorae. To help explain the mystery of the in- frared emission from methane, the team turned to our solar system. Methane in emission is a common feature in gas giants like Jupiter and Saturn. The upper-atmosphere heating that powers this emission is linked to aurorae. On Earth, aurorae are created when energetic particles blown into space from the Sun are captured by Earth’s magnetic field. They cascade T his artist’s concept portrays the brown dwarf W1935, which is lo- cated 47 light-years from Earth. As- tronomers using NASA’s James Webb Space Telescope found infrared emis- sion from methane coming from W1935. This is an unexpected discov- ery because the brown dwarf is cold and lacks a host star; therefore, there is no obvious source of energy to heat its upper atmosphere and make the methane glow. The team specu- lates that the methane emission may be due to processes generating auro- rae, shown here in red. [NASA, ESA, CSA, Leah Hustak (STScI)] Signs of possible aurorae on isolated brown dwarf American Museum of Natural His- tory in New York, was awarded time with the Webb telescope to investi- gate 12 cold brown dwarfs. Among those were W1935 – an object that was discovered by citizen scientist Dan Caselden, who worked with the Backyard Worlds Zooniverse project – and W2220, an object that was discovered using NASA’s Wide Field