HAT-P-7

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]

HAT-P-7

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
Companion	B
Semi-major axis (a)	730 AU
Orbit[7]
Primary	A
Companion	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.

The HAT-P-7 planetary system^[11]

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

See also

• HATNet Project
• Kepler Mission