JWST spots rogue planet's atmosphere heated by stunning auroras, far from Sun

Illustration depicting the rogue planet SIMP-0136. (Image: Chuck Carter, Caltech, NRAO/AUI/NSF)

What can auroras tell astronomers about starless planets? A recent study analyzed a close-by rogue planet, SIMP-0136, and found its extreme temperatures and strange atmospheric properties. The research provides a glimpse into the formation and evolution of free-floating planets that is extremely rare.

How Do Rogue Planet Auroras Heat the Atmosphere?

Why is SIMP-0136 hotter than Jupiter or Saturn? Using NASA’s James Webb Space Telescope, researchers observed auroras warming the rogue planet’s upper atmosphere. The team found constant cloud coverage, unlike Earth’s ever-changing skies. Dr Evert Nasedkin, lead author, said the measurements were among the most precise for any extrasolar object. The clouds consist of silicate grains, similar to sand, instead of water or ice particles.

What Makes SIMP-0136’s Atmosphere Unusual?

How does thermal inversion affect this free-floating planet? SIMP-0136’s atmosphere is colder near the surface and hotter higher up. This is a reversal of Earth's normal temperature profile. Spinning on its side every 2.4 hours, the planet made it possible for scientists to monitor changes in temperature and chemical makeup. Such changes indicate storm-like characteristics, similar to Jupiter's Great Red Spot. Prior research found hot spots and differences in chemicals, but the new research connected auroras to these effects directly.

Why Are Rogue Planets Important to Study?

Could rogue planets hold clues to planetary evolution? SIMP-0136 is approximately 12.7 times Jupiter’s mass and located 20 light-years away. Rogue planets do not orbit stars and may have formed as sub-brown dwarfs or been ejected from star systems. Astronomers estimate billions to trillions exist across the Milky Way. They emphasise the low likelihood of any rogue planet threatening Earth. The Nancy Grace Roman Space Telescope, set to launch in 2027, could refine these estimates even more.

What Will Future Observations Reveal?

What surprises are rogue planet auroras waiting to deliver? Scientists look to ongoing monitoring to reveal more about temperature fluctuations, chemical processes, and atmospheric dynamics. SIMP-0136 presents a first-ever chance to observe free-floating planets and the extreme conditions they endure. Scientists seek to extrapolate these results to decipher planetary formation and evolution in the galaxy.