WASP-4

WASP-4 is a G-type main-sequence star approximately 891 light-years away in the constellation of Phoenix.^[4][1][2] Despite its advanced age, the star is rotating rapidly, being spun up by the tides raised by a giant planet on a close orbit.^[8]

WASP-4

Artistic rendering of WASP-4 b
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Phoenix[1]
Right ascension	23h 34m 15.0857s[2]
Declination	−42° 03′ 41.048″[2]
Apparent magnitude (V)	12.468±0.025[3]
Characteristics
Evolutionary stage	Main sequence
Spectral type	G7V[4]
Apparent magnitude (V)	12.468±0.025[3]
Apparent magnitude (B)	13.216±0.020[3]
Variable type	Planetary transit variable[4]
Astrometry
Radial velocity (Rv)	57.61±0.76[2] km/s
Proper motion (μ)	RA: 9.950(12) mas/yr[2] Dec.: −87.620(10) mas/yr[2]
Parallax (π)	3.6623±0.0147 mas[2]
Distance	891 ± 4 ly (273 ± 1 pc)
Details
Mass	0.899+0.033 −0.031[5] M☉
Radius	0.9150+0.0089 −0.0091[5] R☉
Surface gravity (log g)	4.472+0.013 −0.012[5] cgs
Temperature	5488+29 −28[5] K
Metallicity [Fe/H]	−0.050±0.040[6] dex
Rotation	22.2±3.3[6] days
Rotational velocity (v sin i)	2.2+0.6 −1.0[6] km/s
Age	7.0±2.9[6] Gyr
Other designations
1SWASP J233415.06-420341.1, TOI-232, TIC 402026209, WASP-4, TYC 8017-108-1, 2MASS J23341508-4203411[7]
Database references
SIMBAD	data
Exoplanet Archive	data

Planetary system

In 2007 the exoplanet WASP-4b was discovered orbiting this star. With an orbital period of just 1.3 days, it is classified as a hot Jupiter.^[4] The planet's orbital period appears to be decreasing at a rate of 7.33±0.71 milliseconds per year, suggesting that its orbit is decaying, with a decay timescale of 15.77±1.57 million years.^[9] Another superjovian planet in the system is suspected.^[9] A 2025 study further supported orbital decay for WASP-4b,^[5] but another same-year study discounted this, attributing all evidence for orbital decay to the light travel time effect of an outer planet.^[10] This second planet is more massive and closer to the star than was previously proposed, though the parameters also have larger uncertainties.^[10]

The WASP-4 planetary system

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b[5]	1.200+0.032 −0.030 MJ	0.02294+0.00028 −0.00026	1.338230994(84)	0.0013+0.0005 −0.0009	88.05+0.85 −0.53°	1.349+0.011 −0.012 RJ
c[10]	≥9.2+3.8 −1.2 MJ	3.56+0.60 −0.23	2590+740 −270	—	—	—

See also

• SuperWASP
• List of extrasolar planets