K2-21
| Observation data J2000
| |
|---|---|
| Constellation | Aquarius[1] |
| Right ascension | 22h 41m 12.88625s[2] |
| Declination | −14° 29′ 20.3492″[2] |
| Apparent magnitude (V) | 12.85[3] |
| Characteristics | |
| Evolutionary stage | Main sequence |
| Spectral type | M0.0±0.5V[3] |
| Apparent magnitude (B) | 14.14±0.06[3] |
| Apparent magnitude (V) | 12.85±0.02[3] |
| Apparent magnitude (G) | 12.268±0.003[2] |
| Apparent magnitude (J) | 10.251±0.021[4] |
| Apparent magnitude (H) | 9.633±0.022[4] |
| Apparent magnitude (K) | 9.417±0.020[4] |
| Details Gyr | |
| Database references | |
| SIMBAD | data |
K2-21, also known as EPIC 206011691, is a red dwarf star located 273 light-years (84 parsecs) away in the constellation Aquarius. It hosts two known exoplanets, discovered in 2015 by the transit method as part of Kepler's K2 mission.[3] Both planets have significantly lower densities than Earth, indicating that they are not rocky planets and are better described as mini-Neptunes. The inner planet, K2-21b, is less dense than the outer planet, K2-21c.[5]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 1.59+0.52 −0.44 M🜨 |
0.0731+0.0057 −0.0067[3] |
9.3238+0.0002 −0.0001 |
— | 88.54+0.49 −0.59° |
1.93±0.07 R🜨 |
| c | 3.88+1.22 −1.07 M🜨 |
0.1026+0.0079 −0.0094[3] |
15.5017±0.0002 | — | 89.02+0.33 −0.41° |
2.25±0.05 R🜨 |
References
- ^ "Finding the constellation which contains given sky coordinates". djm.cc. 2 August 2008.
- ^ S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ .
- ^ a b c d "K2-21". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 24 May 2023.
- ^ .
2015 in space | ||
|---|---|---|
Space probes |
| |
| Space observatories |
| |
- Aldebaran b
- evaporation of Gliese 436 b
- Gliese 1132 b
- HD 155233 b
- HD 164595 b
- HD 219134
- HIP 11915 b
- K2-3d
- K2-18b
- K2-22b
- K2-24b
- K2-24c
- KELT-4Ab
- Kepler-438b
- Kepler-440b
- Kepler-442b
- Kepler-444
- b
- c
- d
- e
- f
- Kepler-451b
- Kepler-452b
- Kepler-453b
- KOI-4878.01
- LkCa 15 b
- spectrum of 51 Pegasi b
- WASP-121b
- Wolf 1061c
- 2015 BP519
- US 708
- EGS-zs8-1 (announced)
- WISE J224607.57−052635.0
- 1SWASP J093010.78+533859.5
- ASASSN-15lh
- EGSY8p7
- Tabby's Star
- 541132 Leleākūhonua
- VFTS 352 contact binary
- GW150914 (first observation of gravitational waves)
- GW151226
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