K2-138
K2-138, also designated EPIC 245950175 or EE-1, is a large early K-type main sequence star with a system of at least 6 planets discovered by citizen scientists. Four were found in the first two days of the Exoplanet Explorers project on Zooniverse in early April 2017, while two more were revealed in further analysis. The system is about 660 light-years (200 parsecs) away in the constellation Aquarius, within K2 Campaign 12.
Artist’s impression of the K2-138 exoplanetary system | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 23h 15m 47.76861s |
| Declination | −10° 50′ 58.8955″ |
| Apparent magnitude (V) | 12.21 |
| Characteristics | |
| Evolutionary stage | Main sequence |
| Spectral type | K1V |
| Astrometry | |
| Radial velocity (Rv) | 0.77±0.49 km/s |
| Proper motion (μ) | RA: −1.080 mas/yr Dec.: −10.675 mas/yr |
| Parallax (π) | 4.9437 ± 0.0150 mas |
| Distance | 660 ± 2 ly (202.3 ± 0.6 pc) |
| Details | |
| Mass | 0.93 ± 0.06 M☉ |
| Radius | 0.86 ± 0.08 R☉ |
| Luminosity | ~0.554 L☉ |
| Surface gravity (log g) | 4.59 ± 0.07 cgs |
| Temperature | 5378 ± 60 K |
| Metallicity [Fe/H] | +0.16 ± 0.04 dex |
| Age | 2.3+0.44 −0.36 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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