'244 light-years away’: NASA's James Webb Telescope detects water vapours in the atmosphere of exoplanet TOI-421b
Produced by Subhadra Srivastava
Produced by Subhadra Srivastava
NASA’s James Webb Space Telescope (JWST) has detected water vapour in the atmosphere of TOI-421 b, a scorching sub-Neptune exoplanet located 244 light-years away, a new study reports.
Sub-Neptunes are smaller than gas giants but they are larger than Earth, and are also among the most commonly detected exoplanets. However, their thick atmospheric haze has long obstructed efforts to study their chemical makeup — until now.
Astronomers targeted TOI-421 b because its high temperature which is estimated to be around 727°C, that suggested a clearer atmosphere. Earlier studies had hinted that hotter sub-Neptunes may lack the haze seen in cooler counterparts, making this planet a promising subject.
Using JWST’s Near Infrared Spectrograph (NIRSpec) and Near Infrared Imager (NIRISS), scientists recorded the planet’s transmission spectrum during two transits. The result clearly showed a detailed atmospheric profile with clear chemical signals.
Water vapour was clearly identified, alongside hints of carbon monoxide and sulphur dioxide. Notably, methane and carbon dioxide were absent. The study adds that a hydrogen-rich atmosphere was also observed — one that closely resembles the host star’s composition.
The findings call into question the current models of sub-Neptune formation and their evolution. Particularly, the hydrogen-heavy composition suggests the planet’s atmosphere may have formed directly from the protoplanetary disc.
Sub-Neptunes were once spectral enigmas. Now, with JWST’s capabilities, researchers are beginning to unravel their mysteries conduct in-dept studies on them. This discovery marks a significant step in understanding the nature, space as well as the diversity of planets beyond our Solar System.