| Discovery | |
|---|---|
| Discovered by | Teruyuki Hirano et al. [1] |
| Discovery site | Tokyo Institute of Technology |
| Discovery date | March 2018 |
| Transit method | |
| Designations | |
| LP 415-17 c, EPIC 210897587 c[2] | |
| Orbital characteristics | |
| 0.1886 (± 0.0066)[3] AU | |
| Eccentricity | unknown |
| 40.6835 (± 0.0031)[3] d | |
| Inclination | unknown |
| Star | K2-155 |
| Physical characteristics | |
| 1.64 +0.18 −0.17[3] R🜨 | |
Mean density | 5.41±1.11 g/cm3 |
| Temperature | 289 K (16 °C; 61 °F)[4] |
K2-155d is a potentially habitable Super-Earth exoplanet in the K2-155 system.[5] It is the outermost of three known planets orbiting around the K-type star K2-155 in the constellation Taurus.[6] It is one of 15 new exoplanets around red dwarf stars discovered by Japanese astronomer Teruyuki Hirano of the Tokyo Institute of Technology and his team.[1] The team used data from NASA's Kepler Space Telescope during its extended K2 "Second Light" mission. K2-155d orbits near the so-called habitable zone of its system, and has the potential to host liquid water.[7][5]
K2-155d is one of 15 exoplanets discovered by a team of Japanese astronomers led by Teruyuki Hirano at the Tokyo Institute of Technology.[5] Its discovery is based on data from the K2 mission of NASA's Kepler spacecraft.[5] The exoplanet has also been observed from ground-based telescopes including the Nordic Optical Telescope (NOT) in La Palma and the Subaru Telescope in Hawaii.[5] Its characteristics were confirmed using speckle imaging and high-dispersion optical spectroscopy.[3] The mass of K2-155d and the brightness of its host star may be measured by future observations from the W. M. Keck Observatory and the James Webb Space Telescope.[3] The brightness of its host star makes K2-155d a good target for future studies using instruments such as the James Webb Space Telescope.[3]
K2-155d is a super-Earth exoplanet with a radius 1.64 times that of Earth, near the transition zone between small rock-based and larger gaseous planets.[8][3][7] Climate models predict that it is located near its star's habitable zone and has an insolation 1.67 ± 0.38 (between 1.29 and 2.05) times that of Earth.[3] Its physical temperature is estimated to be 289 K (16 degrees Celsius or 61 degrees Fahrenheit).[4] Studies have shown that the planet would maintain a moderate surface temperature if its insolation is smaller than ~1.5 times that of Earth.[3]
K2-155d is one of three known planets in the system orbiting K2-155, a red dwarf star located 62.3 parsecs (203 ly) from Earth.[3] Its parent star has 88% less volume than the Sun.[9] K2-155d orbits its star with a 40.7 day period, but as the planet is tidally locked the same side always faces its sun.[5] K2-155d has an orbital radius of 0.1886 AU[8] and studies suggest that the planet has a low orbital eccentricity.[10]
K2-155d has been labeled a potentially habitable planet that may be able to harbor liquid water.[7][5] A three-dimensional climate simulation was used to confirm the possibility of the existence of water.[5] However, its discoverer Teruyuki Hirano was cautious about the findings, stating that they do not guarantee K2-155d is habitable, as the ranges in its orbit and temperature allow the possibility of it being outside the habitable zone.[7] Factors such as the absence of solar flares could also decide if K2-155d is habitable.[5]
