TOI-270
TOI-270, also known as L 231-32, is a red dwarf star away in the constellation Pictor. It has about 39% the mass and 38% the radius of the Sun, and a temperature of about. TOI-270 hosts a system of three known exoplanets.
Planetary system
The three planets of TOI-270 were discovered in 2019 by the transit method with TESS. Their masses have since been measured by both Doppler spectroscopy and transit-timing variations. The innermost planet, TOI-270 b, is a volatile-rich super-Earth, while the two outer planets are mini-Neptunes. TOI-270 b and c orbit near a 5:3 resonance, while TOI-270 c and d orbit near a 2:1 resonance.Observations of the outermost planet, TOI-270 d, by the Hubble Space Telescope suggest a hydrogen-rich atmosphere with signs of water vapor. TOI-270 c & d are good targets for atmospheric detection with the James Webb Space Telescope.
The JWST detected methane, carbon dioxide and water vapor in the atmosphere of TOI-270 d. The atmosphere of this planet was also found to be metal-rich, with a mean molecular weight of and an atmospheric metal mass fraction of. Possible signatures of sulfur dioxide and carbon disulfide were also found. It was found that TOI-270 b possibly has an atmosphere rich in water vapor based on the revised density value and JWST transmission spectroscopy result.