HIP 107773

HIP 107773 is a star located 344 light years from Earth in the southern constellation Indus.^[3] It is classified as a horizontal branch K-type giant star,^[3][4] having a spectral type K0III^[2] and a radius of 11.6 R_☉.^[6] With an apparent magnitude of 5.6, the star can be faintly seen with the naked eye.^[2] It has an exoplanet, HIP 107773 b, a gas giant orbiting it at a distance of 0.72 astronomical units (108,000,000 km),^[7] about the same distance from Venus to the Sun.^[a]

HIP 107773

Location of HIP 107773 in Indus (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Indus[1]
Right ascension	21h 50m 0.12s[2]
Declination	−64° 42′ 45.1″[2]
Apparent magnitude (V)	5.6[2]
Characteristics
Evolutionary stage	Horizontal branch[3][4]
Spectral type	K0III[2]
B−V color index	0.99[5]
Astrometry
Radial velocity (Rv)	−0.1701±0.1237[6] km/s
Proper motion (μ)	RA: −0.7032±0.0807 mas/yr[6] Dec.: −37.4432±0.0893 mas/yr[6]
Parallax (π)	9.5919 mas[2]
Distance	343.9±2.6 ly (105.5±0.8 pc)[3]
Absolute magnitude (MV)	0.54[5]
Details[4]
Mass	2.42±0.27 M☉
Radius	11.6±1.4 R☉
Luminosity	74.13+1.12 −1.15 L☉
Surface gravity (log g)	2.6±0.2 cgs
Temperature	4945±100 K
Age	>1[3] Gyr
Other designations
2MASS J21500013-6442451, FK5 3742, HD 207229, HR 8331, IRAS 21461-6456, PPM 365403, SAO 255080, TIC 406320735, TYC 9119-2234-1[2]
Database references
SIMBAD	data

Characteristics

HIP 107773 is a giant star, having a spectral type K0III,^[2] where K0 means it is a K-type star and III (luminosity class) means it is a giant star. The star is in the horizontal branch phase of evolution.^[4][3] HIP 107773 has a radius equivalent to 11.6 solar radii, and a mass equivalent to about 2.4 solar masses.^[4] It is cooler than the Sun, having an effective temperature of 4,945 K (4,672 °C).^[4][b] Given the mass and the evolutionary stage of the star, its age is estimated to be at least about one billion years.^[3]

Planetary system

HIP 107773 has an exoplanet, HIP 107773 b, discovered in 2015 using the radial velocity method.^[7][4] The planet is classified as a gas giant, having a minimum mass of 2 M_J^[4] and an estimated radius of 1.19 R_J.^[7] It orbits its star at a distance of 0.72 astronomical units (108,000,000 km), about the same distance as Venus is from the Sun,^[a] and completes one orbit every 144 days (0.39 years).^[4] Its orbit is almost circular, with an eccentricity of just 0.09.^[4]

With a mass of 2.4 M_☉, the star HIP 107773 is one of the most massive stars with a close-in planet.^[4][10]

The HIP 107773 planetary system^[4]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥1.98±0.21 MJ	0.72±0.03	144.3±0.5	0.09±0.06	—	1.19 (estimate)[7] RJ

See also

• List of exoplanets discovered in 2015
• List of stars in Indus

Notes

1. The distance from Venus to the Sun is 0.723 AU.^[8]
2. For comparison, the effective temperature of the Sun is 5,772 K (5,499 °C).^[9]