HAT-P-8

HAT-P-8 is a magnitude 10 star located 700 light-years away in Pegasus.^[3] It is a F-type star about 28% more massive than the Sun.^[4] Two red dwarf companions have been detected around HAT-P-8. The first has a spectral type of M5V and has a mass of 0.22 M_☉. The second is even less massive, at 0.18 M_☉, and its spectral type is M6V.^[7]

HAT-P-8

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Pegasus[1]
Right ascension	22h 52m 09.8636s[2]
Declination	+35° 26′ 49.608″[2]
Apparent magnitude (V)	10.17[3]
Characteristics
Spectral type	F[4]
Apparent magnitude (B)	10.77 ± 0.04[3]
Apparent magnitude (V)	10.36 ± 0.03[3]
Apparent magnitude (J)	9.214 ± 0.022[3]
Apparent magnitude (H)	9.004 ± 0.018[3]
Apparent magnitude (K)	8.953 ± 0.013[3]
Variable type	planetary transit[4]
Astrometry
Radial velocity (Rv)	−22.2±0.3[2] km/s
Proper motion (μ)	RA: 74.676(19) mas/yr[2] Dec.: 14.944(20) mas/yr[2]
Parallax (π)	4.6606±0.0208 mas[2]
Distance	700 ± 3 ly (214.6 ± 1.0 pc)
Details
Mass	1.27±0.03[5] M☉
Radius	1.491+0.016 −0.014[5] R☉
Surface gravity (log g)	4.1956+0.0095 −0.013[5] cgs
Temperature	6410±140[5] K
Metallicity [Fe/H]	-0.018+0.0072 −0.056[5] dex
Rotational velocity (v sin i)	12.6 ± 1.0[6] km/s
Age	3.4 ± 1 Gyr
Other designations
Gaia DR3 1891507552826485632, TYC 2757-1152-1, GSC 02757-01152, 2MASS J22520985+3526495[3]
Database references
SIMBAD	data

Planetary system

In 2008 the HATNet Project announced the discovery of extrasolar planet HAT-P-8b around this star. This planet is a hot Jupiter gas giant planet.^[4]

The HAT-P-8 planetary system^[8][9]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	1.354±0.035 MJ	0.04496+0.00046 −0.00045	3.0763458±0.0000024	<0.0060	—	1.334±0.013[5] RJ

See also

• HATNet Project
• List of extrasolar planets