Article · Wikipedia archive · Last revised Jul 20, 2026

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. Despite its advanced age, the star is rotating rapidly, being spun up by the tides raised by a giant planet on a close orbit.

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Jul 20, 2026
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WASP-50 / Chaophraya
Observation data
Epoch J2000      Equinox J2000
Constellation Eridanus1
Right ascension 02h 54m 45.1342s2
Declination −10° 53′ 53.025″2
Apparent magnitude (V) 11.443
Characteristics
Evolutionary stage main sequence2
Spectral type G9V4
Astrometry
Radial velocity (Rv)25.76±0.692 km/s
Proper motion (μ) RA: 3.383(20) mas/yr2
Dec.: 8.913(17) mas/yr2
Parallax (π)5.4865±0.0174 mas2
Distance594 ± 2 ly
(182.3 ± 0.6 pc)
Details
Mass0.892+0.08
−0.0745 M☉
Radius0.843±0.0315 R☉
Luminosity0.66 L☉
Surface gravity (log g)4.5±0.14 cgs
Temperature5,400±1004 K
Metallicity−0.12±0.084
Rotation16.30±0.50 d7
Rotational velocity (v sin i)2.6±0.54 km/s
Age8.57±2.867 Gyr
Other designations
Chaophraya, TOI-391, TIC 382391899, WASP-50, TYC 5290-462-1, GSC 05290-00462, 2MASS J02544513-10535303
Database references
SIMBADdata
Exoplanet Archivedata

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

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.89 The Thai names Chaophraya (เจ้าพระยา) and Maeping (แม่ปิง) were proposed by Duangrat Wichiansri (ดวงรัตน์ วิเชียรศรี) following a national vote conducted by NARIT in 2019,1011

Planetary system

In 2011 a transiting hot superjovian planet, WASP-50b (named Maeping in 20198) 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 system513
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
−0.00614 		84.88±0.27 1.138±0.026 RJ
References

References

  1. Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
  2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. "WASP-50". SIMBAD. Centre de données astronomiques de Strasbourg.
  4. Gillon, M.; Doyle, A. P.; Lendl, M.; Maxted, P. F. L.; Triaud, A. H. M. J.; Anderson, D. R.; Barros, S. C. C.; Bento, J.; Collier-Cameron, A.; Enoch, B.; Faedi, F.; Hellier, C.; Jehin, E.; Magain, P.; Montalban, J.; Pepe, F.; Pollacco, D.; Queloz, D.; Smalley, B.; Segransan, D.; Smith, A. M. S.; Southworth, J.; Udry, S.; West, R. G.; Wheatley, P. J. (2011), "WASP-50 b: a hot Jupiter transiting a moderately active solar-type star", Astronomy & Astrophysics, 533: A88, arXiv:1108.2641, Bibcode:2011A&A...533A..88G, doi:10.1051/0004-6361/201117198, S2CID 46639973
  5. Chakrabarty, Aritra; Sengupta, Sujan (2019), "Precise Photometric Transit Follow-up Observations of Five Close-in Exoplanets: Update on Their Physical Properties", The Astronomical Journal, 158 (1): 39, arXiv:1905.11258, Bibcode:2019AJ....158...39C, doi:10.3847/1538-3881/ab24dd, S2CID 166227769
  6. Johns, Daniel; Marti, Connor; Huff, Madison; McCann, Jacob; Wittenmyer, Robert A.; Horner, Jonathan; Wright, Duncan J. (2018). "Revised Exoplanet Radii and Habitability Using Gaia Data Release 2". The Astrophysical Journal Supplement Series. 239 (1): 14. arXiv:1808.04533. Bibcode:2018ApJS..239...14J. doi:10.3847/1538-4365/aae5fb.
  7. Maxted, P. F. L.; Serenelli, A. M.; Southworth, J. (2015), "A comparison of gyrochronological and isochronal age estimates for transiting exoplanet host stars", Astronomy & Astrophysics, 577: A90, arXiv:1503.09111, Bibcode:2015A&A...577A..90M, doi:10.1051/0004-6361/201525774, S2CID 53324330
  8. "Two celestial objects named Chao Phraya and Maeping". nationthailand.com. 19 December 2019. Retrieved 2020-07-30.
  9. "Approved names". NameExoWorlds. IAU. Retrieved 24 June 2025.
  10. Thai PBS (2019-12-21). ""เจ้าพระยา - แม่ปิง ดาวเคราะห์นอกระบบสุริยะชื่อไทย"". Thai PBS. Retrieved 2025-06-29.
  11. Workpoint Today (2019-12-17). ""สหพันธ์ดาราศาสตร์นานาชาติ ตั้งชื่อไทย 'เจ้าพระยา–แม่ปิง'"". Workpoint Today. Retrieved 2025-06-29.
  12. Blažek, Martin; Kabáth, Petr; Piette, Anjali A A; Madhusudhan, Nikku; Skarka, Marek; Šubjak, Ján; Anderson, David R; Boffin, Henri M J; Cáceres, Claudio C; Gibson, Neale P; Hoyer, Sergio; Ivanov, Valentin D; Rojo, Patricio M (2022-04-09). "Constraints on TESS albedos for five hot Jupiters". Monthly Notices of the Royal Astronomical Society. 513 (3): 3444–3457. arXiv:2204.03327. doi:10.1093/mnras/stac992. ISSN 0035-8711.
  13. Tregloan-Reed, Jeremy; Southworth, John (2012), "An extremely high photometric precision in ground-based observations of two transits in the WASP-50 planetary system", Monthly Notices of the Royal Astronomical Society, 431 (1): 966–971, arXiv:1212.0686, Bibcode:2013MNRAS.431..966T, doi:10.1093/mnras/stt227, S2CID 118869498
  14. Knudstrup, E.; Albrecht, S. H.; et al. (October 2024). "Obliquities of exoplanet host stars: Nineteen new and updated measurements, and trends in the sample of 205 measurements". Astronomy & Astrophysics. 690: A379. arXiv:2408.09793. Bibcode:2024A&A...690A.379K. doi:10.1051/0004-6361/202450627.