WASP-4

WASP-4

Artistic rendering of WASP-4 b
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Phoenix
Right ascension 23h 34m 15.0857s
Declination −42° 03′ 41.048″
Apparent magnitude (V) 12.468±0.025
Characteristics
Evolutionary stage Main sequence
Spectral type G7V
Apparent magnitude (V) 12.468±0.025
Apparent magnitude (B) 13.216±0.020
Variable type Planetary transit variable
Astrometry
Radial velocity (Rv)57.61±0.76 km/s
Proper motion (μ) RA: 9.950(12) mas/yr
Dec.: −87.620(10) mas/yr
Parallax (π)3.6623±0.0147 mas
Distance891 ± 4 ly
(273 ± 1 pc)
Details
Mass0.899+0.033
−0.031 M☉
Radius0.9150+0.0089
−0.0091 R☉
Surface gravity (log g)4.472+0.013
−0.012 cgs
Temperature5,488+29
−28 K
Metallicity [Fe/H]−0.050±0.040 dex
Rotation22.2±3.3 days
Rotational velocity (v sin i)2.2+0.6
−1.0 km/s
Age7.0±2.9 Gyr
Other designations
1SWASP J233415.06-420341.1, TOI-232, TIC 402026209, WASP-4, TYC 8017-108-1, 2MASS J23341508-4203411
Database references
SIMBADdata
Exoplanet Archivedata

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

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. 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. Another superjovian planet in the system has been suspected. A 2025 study further supported orbital decay for WASP-4b, but another same-year study discounted this, attributing all evidence for orbital decay to the light travel time effect of an outer planet. Although the previous candidate has not been addressed, this planet has nearly the same orbital elements and thus both should be the same object.

The WASP-4 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination
(°)		 Radius
b 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 ≥6.93+1.10
−0.47 MJ		 7.96+0.72
−0.32		 8,650+1,200
−510		 — — —

See also

References

  1. 1 2 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. 1 2 3 4 5 6 7 8 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. 1 2 3 Henden, A. A.; et al. (2016). "VizieR Online Data Catalog: AAVSO Photometric All Sky Survey (APASS) DR9 (Henden+, 2016)". VizieR On-line Data Catalog: II/336. Originally Published in: 2015AAS...22533616H. 2336. Bibcode:2016yCat.2336....0H. Vizier catalog entry Archived 2018-09-23 at the Wayback Machine
  4. 1 2 3 4 Wilson, D. M.; et al. (2008). "WASP-4b: A 12th Magnitude Transiting Hot Jupiter in the Southern Hemisphere". The Astrophysical Journal Letters. 675 (2): L113–L116. arXiv:0801.1509. Bibcode:2008ApJ...675L.113W. doi:10.1086/586735. S2CID 10823235.
  5. 1 2 3 4 5 6 Baştürk, Ö; Kutluay, A. C.; Barker, A.; Yalçınkaya, S.; Southworth, J.; Barkaoui, K.; Wünsche, A.; Burgdorf, M. J.; Timmermans, M. (2025-06-17). "The Orbit of WASP-4 b is in Decay". Monthly Notices of the Royal Astronomical Society. 541 (2): 714–730. arXiv:2506.15022. doi:10.1093/mnras/staf1009.
  6. 1 2 3 4 Bonomo, A. S.; Desidera, S.; et al. (June 2017). "The GAPS Programme with HARPS-N at TNG. XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets". Astronomy & Astrophysics. 602: A107. arXiv:1704.00373. Bibcode:2017A&A...602A.107B. doi:10.1051/0004-6361/201629882.
  7. ↑ "WASP-4". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-09-22.
  8. ↑ 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
  9. 1 2 Turner, Jake D.; Flagg, Laura; Ridden-Harper, Andrew; Jayawardhana, Ray (2022), "Characterizing the WASP-4 System with TESS and Radial Velocity Data: Constraints on the Cause of the Hot Jupiter's Changing Orbit and Evidence of an Outer Planet", The Astronomical Journal, 163 (6): 281, arXiv:2112.09621, Bibcode:2022AJ....163..281T, doi:10.3847/1538-3881/ac686f, S2CID 245329747
  10. 1 2 3 Winn, Joshua N.; Stefánsson, Guđmundur (2025-12-01). "Orbital Decay Candidates Reconsidered: WASP-4 b Is Not Decaying and Kepler-1658 b Is Not a Planet". The Planetary Science Journal. 6 (12): 300. arXiv:2510.05229. doi:10.3847/PSJ/ae21db. ISSN 2632-3338.