.jpg) | |
| Discovery | |
|---|---|
| Discovery site | Kepler space telescope |
| Discovery date | 2015 |
| Transit | |
| Orbital characteristics[1] | |
| 0.15910+0.00046 −0.00047 au21,380,000 km | |
| Eccentricity | 0.09+0.12 −0.09[2] |
| 32.940045±0.000100 d | |
| 354.3°[3] | |
| Star | K2-18 |
| Physical characteristics | |
| 2.610±0.087 R🜨 | |
| Mass | 8.63±1.35 M🜨 |
Mean density | 2.67+0.52 −0.47 g/cm3 |
| 12.43+2.17 −2.07 m/s2 | |
| Temperature | 265 ± 5 K (−8 ± 5 °C) |
K2-18b, also known as EPIC 201912552 b, is an exoplanet orbiting the red dwarf K2-18, located 124 light-years (38 pc) away from Earth. The planet is a sub-Neptune about 2.6 times the radius of Earth, with a 33-day orbit within the star's habitable zone. This means it receives about a similar amount of starlight as the Earth receives from the Sun. Initially discovered with the Kepler space telescope, it was later observed by the James Webb Space Telescope (JWST) in order to study the planet's atmosphere.
In 2019 the presence of water vapour in K2-18b's atmosphere was reported, drawing attention to this system. In 2023, the JWST detected carbon dioxide and methane in the atmosphere of K2-18b. JWST’s data has been variously interpreted as indicating a water ocean planet with a hydrogen-rich atmosphere, and a gas-rich mini-Neptune. K2-18b has been studied as a potential habitable world that, temperature aside, more closely resembles a gas planet like Uranus or Neptune than Earth.
- ^ Benneke et al. 2019, p. 4.
- ^ Blain, Charnay & Bézard 2021, p. 2.
- ^ Martin, Pierre-Yves (2024). "Planet K2-18 b". exoplanet.eu. Retrieved 5 October 2024.