A team of international researchers has used the James Webb Space Telescope (JWST) to explore the exotic atmosphere of LTT 9779 b, a rare “ultra-hot Neptune” that is unusually close to its host star. The study published in Nature Astronomy on February 25th offers new insights into the extreme weather patterns and atmospheric properties of this fascinating exoplanet.
LTT 9779 b orbits its star in less than a day, resulting in scorching temperatures of almost 2,000°C on its dayside. Despite these extremes, the team discovered that the planet’s dayside hosts reflective clouds on its cooler western hemisphere, creating a striking contrast to the hotter eastern side.
The researchers analyzed data from JWST and found an asymmetry in the planet’s dayside reflectivity, which they proposed is driven by powerful winds that transport heat around the planet. This finding helps refine models describing how heat is transported across a planet and cloud formation in exoplanet atmospheres.
To create a clearer picture of the atmosphere, the team observed LTT 9779 b at multiple positions in its orbit and analyzed its properties at each phase individually. They discovered clouds made of materials like silicate minerals, which form on the cooler western side of the dayside. These reflective clouds help explain why this planet is so bright at visible wavelengths.
The study also detected water vapor in the atmosphere, providing important clues about the planet’s composition and the processes that govern its extreme environment. By modeling LTT 9779 b’s atmosphere in detail, scientists are starting to unlock the processes driving its alien weather patterns.
This rare planetary system continues to challenge scientists’ understanding of how planets form, migrate, and endure in the face of unrelenting stellar forces. The discovery provides a unique laboratory for exploring these questions, offering insights into the broader processes that shape the architecture of planetary systems across the galaxy.
Source: https://phys.org/news/2025-02-jwst-uncovers-rare-ultra-hot.html