A team of researchers led by Louis-Philippe Coulombe has used the James Webb Space Telescope (JWST) to explore the exotic atmosphere of LTT 9779 b, a rare “ultra-hot Neptune.” The results, set to be published on February 25th in Nature Astronomy, offer new insights into the extreme weather patterns and atmospheric properties of this fascinating exoplanet.
LTT 9779 b orbits its host star in less than a day, subjecting it to scorching temperatures of almost 2,000°C on its dayside. The planet is tidally locked, meaning one side constantly faces its star while the other remains in perpetual darkness. Despite these extreme conditions, Coulombe’s team discovered reflective clouds on its cooler western hemisphere, creating a striking contrast with the hotter eastern side.
The JWST analysis uncovered an asymmetry in the planet’s dayside reflectivity, suggesting powerful winds transport heat around the planet. This finding helps refine models describing how heat is transported across a planet and cloud formation in exoplanet atmospheres.
By combining reflected light with heat emissions, the team created a detailed model of the planet’s atmosphere, revealing a delicate balance between intense heat from the star and energy redistribution. Water vapor was also detected, providing clues about the planet’s composition and extreme environment.
The study highlights the JWST’s incredible power in studying exoplanet atmospheres. The Canadian instrument, Near Infrared Imager and Slitless Spectrograph (NIRISS), observed the planet for nearly 22 hours, capturing its full orbit around its star, including secondary eclipses and a primary transit.
LTT 9779 b is a rare planetary system that continues to challenge scientists’ understanding of how planets form, migrate, and endure under extreme conditions. The findings offer insights into atmospheric dynamics on smaller gas giants and provide a new lens for understanding exoplanet atmospheres.
The research was conducted as part of the NEAT Guaranteed Time Observation program, led by Prof. David Lafrenière.
Source: https://exoplanetes.umontreal.ca/en/jwst-forecasts-partially-cloudy-skies-on-ultra-hot-neptune-ltt-9779-b