WASP-50

WASP-50, also named Chaophraya, is a G-type main-sequence star about 594 light-years away in the constellation Eridanus. The star is older than the Sun and slightly depleted in heavy elements compared to the Sun, and has a close to average starspot activity.^[4] Despite its advanced age, the star is rotating rapidly, being spun up by the tides raised by a giant planet on a close orbit.^[7]

WASP-50 / Chaophraya

Observation data Epoch J2000      Equinox J2000
Constellation	Eridanus[1]
Right ascension	02h 54m 45.1342s[2]
Declination	−10° 53′ 53.025″[2]
Apparent magnitude (V)	11.44[3]
Characteristics
Evolutionary stage	main sequence[2]
Spectral type	G9V[4]
Astrometry
Radial velocity (Rv)	25.76±0.69[2] km/s
Proper motion (μ)	RA: 3.383(20) mas/yr[2] Dec.: 8.913(17) mas/yr[2]
Parallax (π)	5.4865±0.0174 mas[2]
Distance	594 ± 2 ly (182.3 ± 0.6 pc)
Details
Mass	0.892+0.08 −0.074[5] M☉
Radius	0.843±0.031[5] R☉
Luminosity	0.6[6] L☉
Surface gravity (log g)	4.5±0.1[4] cgs
Temperature	5,400±100[4] K
Metallicity	−0.12±0.08[4]
Rotation	16.30±0.50 d[7]
Rotational velocity (v sin i)	2.6±0.5[4] km/s
Age	8.57±2.86[7] Gyr
Other designations
Chaophraya, TOI-391, TIC 382391899, WASP-50, TYC 5290-462-1, GSC 05290-00462, 2MASS J02544513-1053530[3]
Database references
SIMBAD	data
Exoplanet Archive	data

Nomenclature

The designation WASP-50 comes from Wide Angle Search for Planets, a consortium of academic organisations detecting exoplanets using the transit method.

This was one of the systems selected to be named in the 2019 NameExoWorlds campaign during the 100th anniversary of the IAU, which assigned each country a star and planet to be named. This system was assigned to Thailand. The approved names were Chaophraya for the star and Maeping for the planet, after the Chao Phraya and Mae Ping rivers in Thailand.^[8][9] The Thai names Chaophraya (เจ้าพระยา) and Maeping (แม่ปิง) were proposed by Duangrat Wichiansri (ดวงรัตน์ วิเชียรศรี) following a national vote conducted by NARIT in 2019,^[10][11]

Planetary system

In 2011 a transiting hot superjovian planet, WASP-50b (named Maeping in 2019^[8]) was detected.^[4] In 2022 its albedo was found to be no more than 0.44, meaning that the planet reflects less than 44% of the light irradiated by its host star. This allows the planetary equilibrium temperature to be constrained at 1393±42 K.^[12]

The WASP-50 planetary system^[5][13]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b / Maeping	1.437±0.068 MJ	0.0293±0.0013	1.955100±0.000005	0.009+0.011 −0.006[14]	84.88±0.27°	1.138±0.026 RJ