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.

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. The tertiary is also a red dwarf with a mass of at least ; it is in a highly-eccentric orbit with a semi-major axis of 32 AU.
The secondary star, component B, was discovered in 2012. Another companion was suspected based on long-period radial velocity variations, but its nature was unknown until 2025, when it was found to be a third star.
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.

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 and was given the designation KOI-2 and later Kepler-2.