JWST reveals no clear atmosphere features on rocky planet LTT 1445 A b

Star system: Gliese 3192 A | Distance from the Sun: 22.4 light years

LTT 1445 A b is the closest known rocky planet orbiting a red dwarf star. Scientists used the James Webb Space Telescope (JWST) to observe the planet as it passed in front of its star, measuring how starlight filtered through its atmosphere at wavelengths between three and five micrometers. Two independent data analysis methods were used to ensure the results were reliable. The observations achieved very high precision, allowing researchers to look for signs of gases or clouds in the planet’s atmosphere.

The study found no statistically significant features in the transmission spectrum, meaning that if the planet has an atmosphere, it is either very thin, contains clouds that block light, or is made of heavy elements in high amounts. By comparing the data to models, the team placed limits on the possible composition of the atmosphere, ruling out atmospheres with less than about 350 times the metallicity of the Sun if clouds are present above a certain pressure. When combining these results with earlier Hubble Space Telescope data, the limits become even stricter, excluding atmospheres with less than about 500 times solar metallicity.

These findings show that LTT 1445 A b either lacks a detectable atmosphere or has one that is very different from those found in our solar system. Future observations may reveal more about the planet’s atmosphere, especially by looking at its heat emission or using other wavelengths.

Key findings
- JWST observed LTT 1445 A b’s atmosphere with high precision but found no clear features.
- The planet’s atmosphere, if present, must be very metal-rich or hidden by clouds.
- Combined JWST and Hubble data set strict limits on atmospheric composition.
- Two independent data reduction pipelines confirmed the results.
- Future studies may detect other atmospheric properties.

Scientific study

JWST COMPASS Program: The 3--5μm transmission spectrum of LTT 1445 A b (external link)