HD 179070
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lyra[1] |
| Right ascension | 19h 09m 26.8350s[2] |
| Declination | +38° 42′ 50.456″[2] |
| Apparent magnitude (V) | 8.25[3] |
| Characteristics | |
| Spectral type | F6IV[4] |
| Apparent magnitude (J) | 7.229±0.032[5] |
| Apparent magnitude (H) | 7.031±0.023[5] |
| Apparent magnitude (K) | 6.945±0.018[5] |
| Variable type | Planetary transit variable[4] |
| Astrometry | |
| Proper motion (μ) | RA: 28.093(18)[2] mas/yr Dec.: 28.546(20)[2] mas/yr |
| Parallax (π) | 9.2181 ± 0.0173[2] mas |
| Distance | 353.8 ± 0.7 ly (108.5 ± 0.2 pc) |
| Details[6] | |
| Mass | 1.408+0.021 −0.030 M☉ |
| Radius | 1.902+0.018 −0.012 R☉ |
| Luminosity | 5.188+0.142 −0.128 L☉ |
| Surface gravity (log g) | 4.026±0.004 cgs |
| Temperature | 6305±50 K |
| Metallicity [Fe/H] | −0.03±0.10 dex |
| Rotation | 12.62±0.03 d[3] |
| Rotational velocity (v sin i) | 8.4±0.5[3] km/s |
| Age | 2.60±0.16 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 179070 also known as Kepler-21 is a F-type subgiant star. A transiting exoplanet was discovered orbiting this star by the Kepler spacecraft.[4] At a magnitude of 8.25 this was the brightest star observed by Kepler to host a validated planet until the discovery of an exoplanet orbiting in 2018.[3][8]
Planetary system[]
The single known planet orbiting this star was identified as a candidate based on photometry from the first four months of data from the Kepler spacecraft.[9] Confirmation was obtained in 2012 after extensive follow-up observations and analysis of the Kepler light curves.[4]
The calculated density of the planet is approximately 6.4 g cm−3, similar to earth's 5.5 g cm−3, which suggests a rocky composition. With an equilibrium temperature of 2025 Kelvin, the top few-hundred kilometers of the planet is probably molten.[3]
Calculations of the rate of orbital decay from tidal effects results in a decrease in the orbital period of 3.88 milliseconds per year, since this would be a change of only 4 seconds every thousand years it would be undetectable in any reasonable length of time.[10]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 5.08±1.72 M
|