WASP-21
Star in the constellation Pegasus
From Wikipedia, the free encyclopedia
WASP-21, also named Tangra, is a G-type star (spectral type G3V) that has reached the end of its main sequence lifetime.[4][9] It lies approximately 834 light-years away, in the constellation of Pegasus. The star is relatively metal-poor, having 40% of heavy elements compared to the Sun.[9] Kinematically, WASP-21 belongs to the thick disk of the Milky Way.[3] It has an exoplanet named WASP-21b.[10]
Size comparison between Sun and WASP-21 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pegasus[1] |
| Right ascension | 23h 09m 58.25s[2] |
| Declination | +18° 23′ 45.9″[2] |
| Apparent magnitude (V) | 11.58±0.08[3] |
| Characteristics | |
| Evolutionary stage | subgiant[2][4] |
| Spectral type | G3V[5] |
| Astrometry | |
| Radial velocity (Rv) | −89.21±0.46[2] km/s |
| Proper motion (μ) | RA: +17.567(21) mas/yr[2] Dec.: +18.639(18) mas/yr[2] |
| Parallax (π) | 3.9089±0.0197 mas[2] |
| Distance | 834 ± 4 ly (256 ± 1 pc) |
| Absolute magnitude (MV) | 4.97[3] |
| Details | |
| Mass | 0.89±0.071[6] M☉ |
| Radius | 1.136±0.049[6] R☉ |
| Luminosity | 1.4[7] L☉ |
| Surface gravity (log g) | 4.277±0.025[6] cgs |
| Temperature | 5,800±100[3] K |
| Metallicity | −0.4±0.1[3] |
| Metallicity [Fe/H] | −0.46±0.11[3] dex |
| Rotational velocity (v sin i) | 1.5±0.6[3] km/s |
| Age | 12±5[3] Gyr |
| Other designations | |
| Tangra, TOI-5963, TIC 436478932, WASP-21, GSC 01715-00679, 2MASS J23095825+1823459[8] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
A survey in 2012 failed to find any stellar companions to WASP-21.[11]
Naming
In 2019 the WASP-21 system was chosen as part of the NameExoWorlds campaign organised by the International Astronomical Union, which assigned each country a star and planet to be named. WASP-21 was assigned to Bulgaria. The winning proposal named the star Tangra after a deity worshipped by the early Bulgars, and the planet Bendida after a deity worshipped by the Thracians.[12]
Planetary system
In 2010 WASP-21 was discovered to host a hot Jupiter type planet by the Wide Angle Search for Planets (WASP),[3] confirmed by radial velocity by the WASP team in 2010.
Transit-timing variation analysis in 2015 did not find any additional planets in the system.[9]
In 2020, spectroscopic analysis found that the WASP-21b atmosphere is mostly cloudless and contains sodium.[13]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b / Bendida | 0.276 ± 0.018 MJ | 0.0499 ± 0.0013 | 4.322482 | <0.048[14] | 86.97 ± 0.33° | 1.162 RJ |