Atmospheric analysis of LTT 9779 b reveals muted spectral features and cloud presence

LTT 9779 b is an ultrahot Neptune-sized exoplanet that occupies a rare region of space known as the hot Neptune desert, where such planets are seldom found. Despite its intense exposure to radiation from its host star, LTT 9779 b possesses a confirmed atmosphere. A new comprehensive study using data from the James Webb Space Telescope provides a detailed look at the chemical and physical characteristics of this exotic world's atmosphere.

By analyzing a broad range of light wavelengths, the study identifies muted spectral features that indicate the presence of clouds high in the planet's atmosphere. These features were detected by combining data from two different instruments, which allows for a more complete understanding of how light interacts with the gases and particles surrounding the planet.

Atmospheric models suggest that if these clouds are indeed present, they likely consist of small particles and are influenced by vigorous vertical mixing. The researchers determined that the planet's temperature at the terminator - the line dividing day and night - is relatively low, estimated between 560 and 950 Kelvin depending on the chemical model used.

Future observations targeting specific absorption signatures of silicate clouds are expected to provide more definitive answers about the exact composition of the atmosphere and clarify the relationship between the cloud deck and the chemical makeup of the planet.

Key findings
- Muted spectral features indicate a cloudy atmosphere on LTT 9779 b.
- The temperature at the day-night boundary is estimated to be between 560 and 950 Kelvin.
- Atmospheric models suggest the presence of small, sub-micron sized cloud particles.
- Data confirms a high level of vertical mixing within the planetary atmosphere.

Scientific study

Cool, Cloudy Nights on an Ultrahot Neptune: A Panchromatic NIRISS/NIRSpec Transmission Spectrum of LTT 9779 b (external link)