Rogue planet SIMP-0136 displays strong auroral activity similar to Northern Lights

Strong Northern Lights-like activity is the standout feature of today’s weather report, which is coming at you from a strange, extrasolar world, instead of a standard TV studio. That is thanks to astronomers from Trinity College Dublin, who used the NASA/ESA/CSA James Webb Space Telescope to take a close look at the weather of a toasty nearby rogue planet, SIMP-0136.

The exquisite sensitivity of the instruments on board the space-based telescope enabled the team to see minute changes in brightness of the planet as it rotated, which were used to track changes in temperature, cloud cover and chemistry.

Surprisingly, these observations also illuminated SIMP-0136’s strong auroral activity, similar to the Northern Lights here on Earth or the powerful aurora on Jupiter, which heat up its upper atmosphere.

“These are some of the most precise measurements of the atmosphere of any extra-solar object to date, and the first time that changes in the atmospheric properties have been directly measured,” said Dr. Evert Nasedkin, a Postdoctoral Fellow in Trinity College Dublin’s School of Physics, who is the lead author of the research article published in Astronomy & Astrophysics.

“And at over 1,500 °C, SIMP-0136 makes this summer’s heat wave look mild,” he continued.

“The precise observations we made meant we could accurately record temperature changes smaller than 5 °C. These changes in temperature were related to subtle changes in the chemical composition of this free-floating planet, which is suggestive of storms—similar to Jupiter’s Great Red Spot—rotating into view.”

Another surprise finding was the lack of variability of the clouds on SIMP-0136. One might expect changes in the cloud coverage to lead to changes in the atmosphere, similar to observing patches of clouds and blue sky here on Earth.

Instead, the team found that the cloud coverage was constant over the surface of SIMP-0136. At the temperatures of SIMP-0136, these clouds are unlike those on Earth, instead composed of silicate grains, similar to sand on a beach.

This is the first publication from the new “Exo-Aimsir” group led by Prof. Johanna Vos in Trinity’s School of Physics, and includes contributions from all the group members, including Ph.D. candidates Merle Schrader, Madeline Lam and Cian O’Toole.

These data were initially published by a similar team led by Allison McCarthy at Boston University, but the new analysis has revealed more details about the atmosphere.

“Different wavelengths of light are related to different atmospheric features. Similar to observing the changes in color over the surface of Earth, the changes in the color of SIMP-0136 are driven by changes in the atmospheric properties,” added Dr. Nasedkin.

“So by using cutting-edge models, we could infer the temperature of the atmosphere, the chemical composition, and the position of the clouds.”

Prof. Vos said, “This work is exciting because it shows that by applying our state-of-the-art modeling techniques to cutting-edge datasets from JWST, we can begin to piece together the processes that drive weather in worlds beyond our solar system. Understanding these weather processes will be crucial as we continue to discover and characterize exoplanets in the future.”

“While for now these types of spectroscopic variability observations are limited to isolated brown dwarfs, like this one, future observations with the Extremely Large Telescope and eventually the Habitable Worlds Observatory will enable the study of the atmospheric dynamics of exoplanets, from Jupiter-like gas giants to rocky worlds.”