HAT-P-7
Star system in Cygnus
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HAT-P-7 is a triple star system located about 1,088 light-years away in the constellation Cygnus. The apparent magnitude of this star is 10.5, which means it is not visible to the naked eye but can be seen with a small telescope on a clear dark night.[3]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus[1] |
| Right ascension | 19h 28m 59.3539s[2] |
| Declination | +47° 58′ 10.217″[2] |
| Apparent magnitude (V) | 10.46[3] |
| Characteristics | |
| A | |
| Evolutionary stage | Main sequence[4] |
| Spectral type | F6V[5] |
| Apparent magnitude (B) | ~10.90[3] |
| Apparent magnitude (V) | ~10.46[3] |
| Apparent magnitude (J) | 9.555 ± 0.030[3] |
| Apparent magnitude (H) | 9.344 ± 0.029[3] |
| Apparent magnitude (K) | 9.334 ± 0.018[3] |
| Variable type | planetary transit[6] |
| B | |
| Evolutionary stage | Main sequence[7] |
| Spectral type | M5.5V[8] |
| Astrometry | |
| Radial velocity (Rv) | −10.23±0.25[2] km/s |
| Proper motion (μ) | RA: −18.325(14) mas/yr[2] Dec.: 8.851(14) mas/yr[2] |
| Parallax (π) | 2.9991±0.0114 mas[2] |
| Distance | 1,088 ± 4 ly (333 ± 1 pc) |
| Orbit[7] | |
| Primary | A |
| Name | B |
| Semi-major axis (a) | 730 AU |
| Orbit[7] | |
| Primary | A |
| Name | C |
| Semi-major axis (a) | 32+16 −11 AU |
| Eccentricity (e) | 0.76+0.12 −0.26 |
| Details | |
| A | |
| Mass | 1.35±0.22[4] M☉ |
| Radius | 1.994±0.081[4] R☉ |
| Surface gravity (log g) | 3.97±0.08[4] cgs |
| Temperature | 6,532±109[4] K |
| Metallicity [Fe/H] | 0.15±0.08[9] dex |
| Rotational velocity (v sin i) | 5.0±1.2[9] km/s |
| B | |
| Mass | 0.21[7] M☉ |
| C | |
| Mass | 0.19[7] M☉ |
| Other designations | |
| HAT-P-7, BD+47°2846, Kepler-2, KOI-2, KIC 10666592, TOI-1265, TIC 424865156, TYC 3547-1402-1, GSC 03547-01402, 2MASS J19285935+4758102[3] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Stellar system
The primary component of the HAT-P-7 system is an F-type main-sequence star with around 1.35 times the Sun's mass and twice the Sun's radius, hosting one known planet. The secondary is a red dwarf located 730 astronomical units away from the primary, with a spectral type of M5.5V and a mass of 0.21 M☉. The tertiary is also a red dwarf with a mass of at least 0.15 M☉; it is in a highly-eccentric orbit with a semi-major axis of 32 AU.[7]
The secondary star, component B, was discovered in 2012. Another companion (in addition to the second star and the planet) was suspected based on long-period radial velocity variations,[8] but its nature was unknown until 2025, when it was found to be a third star.[7]
Component B has also been referred to as HAT-P-7 East. HAT-P-7 West is another candidate companion, of spectral type M9V or L0V, but it is not confirmed to be associated with the system and is likely an unrelated background star.[10][8]
Planetary system
The primary star has one known planet, HAT-P-7b, a hot Jupiter discovered in 2008. This star system was within the initial field of view of the Kepler planet-hunting spacecraft[6] and was given the designation KOI-2 and later Kepler-2.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 1.806±0.036 MJ | 0.03813±0.00036 | 2.20473539167(1654)[12] | <0.0040 | 83.151+0.030 −0.033° |
1.51±0.02 RJ |