JWST reveals low-metallicity atmosphere and stellar effects for giant planet HATS-75 b

Star system: HATS-75 | Distance from the Sun: 636 light years

HATS-75 b is a giant planet orbiting a red dwarf star, recently studied as part of a program using the James Webb Space Telescope. Scientists observed three transits of the planet, where it passed in front of its star, to analyze its atmosphere. The planet's spectrum showed a deeper transit at shorter wavelengths, which can be caused by hazes in the atmosphere or by features on the star's surface, such as starspots and bright regions.

By comparing different models, researchers found that the best explanation for the observations is a combination of a hazy atmosphere and contamination from unocculted starspots and faculae on the star. This means that the star's surface is not uniform, and this affects the light passing through the planet's atmosphere. The analysis revealed that HATS-75 b has a very low atmospheric metallicity, meaning it contains fewer heavy elements than expected, and a high carbon-to-oxygen ratio. The planet's interior also appears to have poor vertical mixing. Methane, carbon monoxide, and carbon dioxide were detected in the atmosphere, but water vapor was not clearly seen, likely because its signal is hidden by the effects of the star's surface.

These findings highlight the importance of considering the star's surface features when studying exoplanet atmospheres, especially for planets orbiting active red dwarfs like HATS-75 b.

Key findings
- HATS-75 b orbits a red dwarf and has a low-metallicity atmosphere
- Stellar surface features affect the observed spectrum
- Methane, carbon monoxide, and carbon dioxide detected
- Water vapor signal is masked by stellar contamination
- Results show the need to account for starspots and faculae in exoplanet studies

Scientific study

GEMS JWST: HATS-75 b -- A giant planet with a sub-solar metallicity atmosphere orbiting an M-dwarf (external link)