Kepler-18
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 52m 19.0688s |
| Declination | +44° 44′ 46.808″ |
| Apparent magnitude (V) | 14.0 |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | G7[citation needed] |
| Astrometry | |
| Radial velocity (Rv) | −18.40±0.02 km/s |
| Proper motion (μ) | RA: −1.436(14) mas/yr Dec.: −20.341(14) mas/yr |
| Parallax (π) | 2.2804±0.0168 mas |
| Distance | 1,430 ± 10 ly (439 ± 3 pc) |
| Details | |
| Mass | 0.972 ± 0.042 M☉ |
| Radius | 1.108 ± 0.051 R☉ |
| Luminosity | 0.93 L☉ |
| Surface gravity (log g) | 4.32 ± 0.12 cgs |
| Temperature | 5,383 ± 44 K |
| Metallicity [Fe/H] | 0.19 ± 0.06 dex |
| Rotational velocity (v sin i) | <4 km/s |
| Age | 10.0 ± 2.3 Gyr |
| Other designations | |
| KOI-137, KIC 8644288, 2MASS J19521906+4444467, Gaia DR2 2079295583282164992 | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Kepler-18 is a star with a system of three exoplanets, positioned in the northern Constellation of Cygnus. It has an apparent visual magnitude of 14.0, requiring a telescope to view. Based on parallax measurements, it is located at a distance of approximately 1,430 light-years (440 pc). It is drifting closer with a line of sight velocity component of −18.4 km/s.
This is an older star with an estimated age of around ten billion years. It has similar properties to the Sun with almost the same mass and a 10% larger radius. The star is radiating 93% of the Sun's luminosity from its photosphere at an effective temperature of 5,383 K.
Planetary system
The star is orbited by 3 confirmed transiting planets, announced in 2011. In 2021, it was found the orbital plane of Kepler-18d is slowly changing, likely under the gravitational influence of the additional giant planet.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination (°) |
Radius |
|---|---|---|---|---|---|---|
| b | 6.9 ± 3.4 M🜨 | 0.0447 ± 0.0006 | 3.504725 ± 0.000028 | — | 84.92 ± 0.26 | 2.00 ± 0.10 R🜨 |
| c | 17.3 ± 1.9 M🜨 | 0.0752 ± 0.0011 | 7.6415716 | — | 87.68 ± 0.22 | 5.49 ± 0.26 R🜨 |
| d | 16.4 ± 1.4 M🜨 | 0.1172 ± 0.0017 | 14.858941 | — | 88.07 ± 0.1 | 6.98 ± 0.33 R🜨 |