CoRoT-2b’s dayside reveals water and carbon monoxide in complex atmosphere

Star system: CoRoT-2 | Distance from the Sun: 695 light years

CoRoT-2b is a young and unusual hot Jupiter, a giant planet orbiting very close to its star. Using the IGRINS spectrograph on the Gemini South telescope, scientists observed the planet’s dayside just before it passed behind its star. By analyzing the planet’s thermal emission, they detected clear signs of water vapor and carbon monoxide in its atmosphere. The water signal was found with high confidence, and the carbon monoxide was also detected, while other molecules like methane and carbon dioxide were not seen.

The results show that CoRoT-2b’s dayside is not featureless, as earlier low-resolution studies suggested, but instead has a complex atmospheric structure. The study also found a high carbon-to-oxygen ratio and a metallicity lower than the Sun’s, which gives clues about how the planet formed. There is a lack of strong molecular features at shorter wavelengths, possibly due to clouds, high-altitude absorbers, or limitations in the observations. The findings provide the first detailed look at the atmospheric composition of CoRoT-2b and set the stage for future studies of its unusual weather patterns, such as its westward hotspot offset.

These observations highlight the power of high-resolution ground-based spectroscopy for studying exoplanet atmospheres and will help guide future research into the dynamics and chemistry of hot Jupiters.

Key findings
- Water vapor and carbon monoxide detected in CoRoT-2b’s dayside atmosphere.
- No significant signs of methane, carbon dioxide, titanium oxide, or vanadium oxide.
- The planet’s atmosphere has a high carbon-to-oxygen ratio and subsolar metallicity.
- Complex structure revealed, with some wavelengths lacking strong features.
- Results lay groundwork for future studies of atmospheric dynamics and chemistry.

Scientific study

Unraveling the Mystery of the Peculiar and Young Hot Jupiter CoRoT-2b. I. H_2O and CO Detection from Dayside Observations with Gemini-S/IGRINS (external link)