K2-72
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| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius[1] |
| Right ascension | 22h 18m 29.25485s[2] |
| Declination | −09° 36′ 44.3811″[2] |
| Apparent magnitude (V) | 15.37[3] |
| Characteristics | |
| Evolutionary stage | main sequence[3] |
| Spectral type | M2V[4] |
| Astrometry | |
| Radial velocity (Rv) | −42.92±3.35[2] km/s |
| Proper motion (μ) | RA: 195.834 mas/yr[2] Dec.: 74.259 mas/yr[2] |
| Parallax (π) | 15.0346±0.0277 mas[2] |
| Distance | 216.9 ± 0.4 ly (66.5 ± 0.1 pc) |
| Details | |
| Mass | 0.27+0.08 −0.09[5] M☉ |
| Radius | 0.33±0.03[5] R☉ |
| Luminosity | 0.0134[4] L☉ |
| Surface gravity (log g) | 4.83±0.14[6] cgs |
| Temperature | 3360+87 −86[5] K |
| Rotational velocity (v sin i) | 6.07[6] km/s |
| Age | 1.0[7] Gyr |
| Other designations | |
| EPIC 206209135, 2MASS J22182923-0936444 | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
K2-72 (also designated EPIC 206209135) is a cool red dwarf star of spectral class M2V located about 217 light-years (67 parsecs) away from the Earth in the constellation of Aquarius. It is known to host four planets, all similar in size to Earth, with one of them residing within the habitable zone.
K2-72 also has the 2MASS catalogue number J22182923-0936444. Its EPIC (Ecliptic Plane Input Catalog) number is 206209135.
The star's planetary companions were discovered by NASA's Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits move in front of their stars from the perspective of Earth. The name K2-72 derives directly from the fact that the star is the catalogued 72nd star discovered by the K2 mission to have confirmed planets.
The designation b, c, d, and e derives from the order of discovery. The designation of b is given to the first planet orbiting a given star, and e to the last.[8] In the case of K2-72, there were four planets, so only letters b to e are used. At first the planets were all thought to be smaller than Earth. However, in 2017, new analysis by Martinez et al. and Courtney Dressing found that K2-72 was significantly larger than previous estimates, and found that the planets were all larger than Earth, although all are still expected to be rocky.
