TOI-2136 b is a sub-Neptune exoplanet orbiting the nearby red dwarf star TOI-2136.[1] It was discovered in 2022 through transit observations by NASA's TESS and independently validated using ground-based photometry and radial velocity measurements.[1][2] The planet has an orbital period of approximately 7.85 days and lies at a distance of about 108 light-years from Earth.[3][4]
TOI-2136 b is known for its position near the red dwarf for planets predicted by atmospheric mass-loss models and for its potential as a hycean world.[1][2]
Discovery
TOI-2136 b was first identified as the candidate TOI-2136.01 from photometric data collected during TESS's primary mission.[1] The transit signal was detected with an orbital period of 7.85 days around the red dwarf star TOI-2136.[1]
Independent confirmation came from Gan et al. (2022) who used ground-based multi-wavelength photometry, high-angular-resolution imaging, and precise radial-velocity measurements from the CFHT/SPIRou instrument to validate the planet and measure its mass.[1] Kawauchi et al. (2022) validated it using TESS data, ground-based photometry, and radial velocities from the Subaru Telescope's IRD instrument, while also conducting a search for helium in its atmosphere[2] and Beard et al. (2022) provided additional validation using the Habitable-Zone Planet Finder (HPF) on the Hobby-Eberly Telescope, placing an upper mass limit.[5]
Characteristics
The mass–radius combination of TOI-2136 b is compatible with a wide range of interior compositions, from water or ice dominated worlds to gas-enveloped rocky cores.[1] Interior structure models suggest it may retain a small H/He envelope (mass fraction ~1–2%) atop a rocky or icy core. It lies relatively close to the red dwarfs, where thermally driven atmospheric escape is expected to sculpt planetary populations.[1]
TOI-2136 b has also been discussed as a potential Cold Haber World, where microbial life could produce detectable ammonia via a process similar to the Haber process under high-pressure ocean conditions and could be a future target for JWST.[6]