Kepler-47
Kepler-47 is a binary star system in the constellation Cygnus located about 3,420 light-years (1,050 parsecs) away from Earth. The stars have three exoplanets, all of which orbit both stars at the same time, making this a circumbinary system. The first two planets announced are designated Kepler-47b, and Kepler-47c, and the third, later discovery is Kepler-47d. Kepler-47 is the first circumbinary multi-planet system discovered by the Kepler mission. The outermost of the planets is a gas giant orbiting within the habitable zone of the stars. Because most stars are binary, the discovery that multi-planet systems can form in such a system has impacted previous theories of planetary formation.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 41m 11.49832s |
| Declination | +46° 55′ 13.7073″ |
| Apparent magnitude (V) | 15.4 |
| Characteristics | |
| Evolutionary stage | Main sequence |
| Spectral type | G6V / M4V |
| Astrometry | |
| Proper motion (μ) | RA: −3.383 mas/yr Dec.: −10.212 mas/yr |
| Parallax (π) | 0.9540 ± 0.0208 mas |
| Distance | 3,420 ± 70 ly (1,050 ± 20 pc) |
| Orbit | |
| Primary | Kepler-47A |
| Companion | Kepler-47B |
| Period (P) | 7.4483648+0.0000038 −0.0000270 d |
| Semi-major axis (a) | 0.08145+0.00036 −0.00037 AU |
| Eccentricity (e) | 0.0288+0.0015 −0.0013 |
| Inclination (i) | 89.613+0.045 −0.040° |
| Argument of periastron (ω) (secondary) | 226.3+2.8 −2.6° |
| Details | |
| Kepler-47A | |
| Mass | 0.957+0.013 −0.015 M☉ |
| Radius | 0.936±0.005 R☉ |
| Luminosity | 0.840 ± 0.067 L☉ |
| Surface gravity (log g) | 4.488 ± 0.01 cgs |
| Temperature | 5636 ± 100 K |
| Metallicity [Fe/H] | −0.25 ± 0.08 dex |
| Rotational velocity (v sin i) | 4.1+0.5 −0.35 km/s |
| Age | 4–5 Gyr |
| Kepler-47B | |
| Mass | 0.342±0.003 M☉ |
| Radius | 0.338±0.002 R☉ |
| Luminosity | 0.014 ± 0.002 L☉ |
| Surface gravity (log g) | 4.9073 ± 0.0067 cgs |
| Temperature | 3357 ± 100 K |
| Age | 4–5 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| KIC | data |
A group of astronomers led by Jerome Orosz at San Diego State University, including astronomers from Tel-Aviv University in Israel, discovered the planetary system via NASA's Kepler space telescope in 2012. In November 2013, evidence of a third planet orbiting between the planets b and c, Kepler-47d, was announced. Later analyses of transit data from the Kepler space telescope confirmed the existence of Kepler-47d.