View source for WASP-4b

{{Short description|Extrasolar planet in the constellation Phoenix}}
{{Infobox planet
| name                     = WASP-4b
| image                    = Exoplanet Comparison WASP-4 b.png
| caption                  = Size comparison of WASP-4b with Jupiter.
<!-- DISCOVERY           -->
| discovery_ref            = <ref name="Wilson2008"/>
| discoverer               = [[Wide Angle Search for Planets]]
| discovery_site           = [[South African Astronomical Observatory]]
| discovered               = October 31, 2007
| discovery_method         = [[Methods of detecting exoplanets#Transit photometry|Transit photometry]]
<!-- DESIGNATIONS        -->
<!-- ORBITAL             -->
| orbit_ref                = <ref name=Turner2021/>
| apsis                    = astron
| semimajor                = {{val|0.02239|0.00084|ul=AU}}
| eccentricity             = <0.0033<ref name="Bonomo2017"/>
| period                   = {{val|1.338231587|(22)|ul=d}}
| inclination              = {{val|88.02|0.69|u=deg}}
| semi-amplitude           = {{val|232.7|2.5|2.2|ul=m/s}}<ref name="Bonomo2017"/>
| star                     = [[WASP-4]]
<!-- PHYS CHARS          -->
| physical_ref             = <ref name=Turner2021/>
| mean_radius              = {{val|1.312|0.045|ul=Jupiter radius}}
| mass                     = {{val|1.164|0.082|ul=Jupiter mass}}
| density                  = {{val|0.639|0.079|ul=g/cm3}}
| single_temperature       = {{val|1957|68|ul=K}} ({{convert|1957|K|C F|disp=out}})<ref name=Wong2020/>
<!-- ATMOSPHERE          -->
<!-- NOTES               -->
}}
'''WASP-4b''' is an [[exoplanet]], specifically a [[hot Jupiter]], approximately 891 [[light-year]]s away<ref name="GaiaDR3"/> in the [[constellation]] of [[Phoenix (constellation)|Phoenix]].<ref name="Roman1987"/>

==Discovery==
The planet was the discovered by the [[Wide Angle Search for Planets]] team using images taken with the SuperWASP-South project's eight wide-angle cameras located at the [[South African Astronomical Observatory]].<ref name="The Register"/><ref name="BBC News"/><ref name="Wilson2008"/> Analysis of over 4000 images taken between May and November 2006 resulted in the detection of a [[Transit (astronomy)|transit]] occurring every 1.3 days. Follow-up [[radial velocity]] observations using the [[Swiss 1.2-metre Leonhard Euler Telescope]] confirmed that the transiting object was a planet.<ref name="Wilson2008"/>

[[File:WASP-4 b rv.pdf|thumb|275px|The radial velocity trend of WASP-4, caused by the presence of WASP-4 b.|alt=|none]]

==Characteristics==
The [[planetary equilibrium temperature]] would be 1650{{±|30}} K,<ref name=wasp2 /> but the measured dayside temperature is higher, with a 2015 study finding 1900{{±|100}} K<ref name=Zhou2015/> and a 2020 study finding 1957{{±|68}} [[Kelvin|K]].<ref name=Wong2020/>

A study in 2012, utilizing the [[Rossiter–McLaughlin effect]], determined the planetary orbit is probably aligned with the equatorial plane of the star, with misalignment equal to -1{{±|14|12}}°.<ref name="Albrecht2012"/>

==Orbital decay and tidal interactions==
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. The anomalously high rate of orbital decay of WASP-4b was poorly understood as of 2021.<ref name=Turner2021/> In 2025, the planet has been confirmed to have its orbit in decay. This decay is primarily driven by tidal interactions between the planet and its star. Studies based on [[Transit timing variation]]s (TTVs) indicate that the planet’s orbit is shrinking due to energy dissipation caused by stellar tides. A tidal quality factor of approximately 80,000 was derived from these observations, suggesting that the star is more evolved than previously thought. This phenomenon is consistent with a model of tidal dissipation involving [[Asteroseismology|internal gravity waves]] within the star, although further modeling of the star's properties is needed for a complete understanding.<ref>{{cite web |title=The Orbit of WASP-4b is in Decay |url=https://arxiv.org/pdf/2506.15022 | access-date=2025-06-21}}</ref>

==References==
{{reflist|refs=

<ref name="BBC News">{{cite news | author=<!--Staff writer(s); no by-line.--> | title=Astronomer discovers new planets | url=http://news.bbc.co.uk/2/hi/uk_news/scotland/edinburgh_and_east/7070887.stm | work=BBC News | date=2007-10-31 | access-date=2018-09-23 }}</ref>

<ref name="GaiaDR3">{{Cite Gaia DR3|6535499658122055552}}</ref>

<ref name="Roman1987">{{cite journal | title=Identification of a Constellation From a Position | last1=Roman | first1=Nancy G. | journal=Publications of the Astronomical Society of the Pacific | volume=99 | issue=617 | pages=695–699 | year=1987 | bibcode=1987PASP...99..695R | bibcode-access=free | doi=10.1086/132034 | doi-access=free }} [http://vizier.u-strasbg.fr/vizier/VizieR/constellations.htx Vizier query form ]</ref>

<ref name="The Register">{{cite news | last=Sherriff | first=Lucy | title=UK boffins ID three new exo-planets | url=https://www.theregister.co.uk/2007/10/31/superwasp_planets/ | work=The Register | date=2007-10-31 | access-date=2018-09-23 }}</ref>

<ref name="Wilson2008">{{cite journal | title=WASP-4b: A 12th Magnitude Transiting Hot Jupiter in the Southern Hemisphere | last1=Wilson | first1=D. M. | last2=Gillon | first2=M. | last3=Hellier | first3=C. | last4=Maxted | first4=P. F. L. | last5=Pepe | first5=F. | last6=Queloz | first6=D. | last7=Anderson | first7=D. R. | last8=Collier Cameron | first8=A. | last9=Smalley | first9=B. | last10=Lister | first10=T. A. | last11=Bentley | first11=S. J. | last12=Blecha | first12=A. | last13=Christian | first13=D. J. | last14=Enoch | first14=B. | last15=Haswell | first15=C. A. | last16=Hebb | first16=L. | last17=Horne | first17=K. | last18=Irwin | first18=J. | last19=Joshi | first19=Y. C. | last20=Kane | first20=S. R. | last21=Marmier | first21=M. | last22=Mayor | first22=M. | last23=Parley | first23=N. | last24=Pollacco | first24=D. | last25=Pont | first25=F. | last26=Ryans | first26=R. | last27=Segransan | first27=D. | last28=Skillen | first28=I. | last29=Street | first29=R. A. | last30=Udry | first30=S. | display-authors=1 | journal=The Astrophysical Journal Letters | volume=675 | issue=2 | pages=L113–L116 | year=2008 | arxiv=0801.1509 | bibcode=2008ApJ...675L.113W | bibcode-access=free | doi=10.1086/586735 | doi-access=free }}</ref>

<ref name=wasp2>Table 3, Improved parameters for the transiting hot Jupiters WASP-4b and WASP-5b, M. Gillon et al., ''Astronomy and Astrophysics'' '''496''', #1 (2009), pp. 259–267, {{doi|10.1051/0004-6361:200810929}}, {{Bibcode|2009A&A...496..259G}}.</ref>

<ref name="Albrecht2012">{{citation|arxiv=1206.6105|title=Obliquities of Hot Jupiter Host Stars: Evidence for Tidal Interactions and Primordial Misalignments|year=2012|doi=10.1088/0004-637X/757/1/18 |last1=Albrecht |first1=Simon |last2=Winn |first2=Joshua N. |last3=Johnson |first3=John A. |last4=Howard |first4=Andrew W. |last5=Marcy |first5=Geoffrey W. |last6=Butler |first6=R. Paul |last7=Arriagada |first7=Pamela |last8=Crane |first8=Jeffrey D. |last9=Shectman |first9=Stephen A. |last10=Thompson |first10=Ian B. |last11=Hirano |first11=Teruyuki |last12=Bakos |first12=Gaspar |last13=Hartman |first13=Joel D. |journal=The Astrophysical Journal |volume=757 |issue=1 |page=18 |bibcode=2012ApJ...757...18A |s2cid=17174530 }}</ref>

<ref name=Zhou2015>{{cite journal|arxiv=1509.04147|doi=10.1093/mnras/stv2138|title=Secondary eclipse observations for seven hot-Jupiters from the Anglo-Australian Telescope|year=2015|last1=Zhou|first1=G.|last2=Bayliss|first2=D. D. R.|last3=Kedziora-Chudczer|first3=L.|last4=Tinney|first4=C. G.|last5=Bailey|first5=J.|last6=Salter|first6=G.|last7=Rodriguez|first7=J.|journal=Monthly Notices of the Royal Astronomical Society|volume=454|issue=3|pages=3002–3019|doi-access=free |bibcode=2015MNRAS.454.3002Z}}</ref>

<ref name="Bonomo2017">{{cite journal |last1=Bonomo |first1=A. S. |last2=Desidera |first2=S. |display-authors=etal |date=June 2017 |title=The GAPS Programme with HARPS-N at TNG. XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets |journal=[[Astronomy & Astrophysics]] |volume=602 |issue= |pages=A107 |doi=10.1051/0004-6361/201629882 |arxiv=1704.00373 |bibcode=2017A&A...602A.107B|s2cid=118923163 }}</ref>

<ref name=Wong2020>{{citation|arxiv=2003.06407|title=Systematic Phase Curve Study of Known Transiting Systems from Year One of the TESS Mission|year=2020|doi=10.3847/1538-3881/ababad |last1=Wong |first1=Ian |last2=Shporer |first2=Avi |last3=Daylan |first3=Tansu |last4=Benneke |first4=Björn |last5=Fetherolf |first5=Tara |last6=Kane |first6=Stephen R. |last7=Ricker |first7=George R. |last8=Vanderspek |first8=Roland |last9=Latham |first9=David W. |last10=Winn |first10=Joshua N. |last11=Jenkins |first11=Jon M. |last12=Boyd |first12=Patricia T. |last13=Glidden |first13=Ana |last14=Goeke |first14=Robert F. |last15=Sha |first15=Lizhou |last16=Ting |first16=Eric B. |last17=Yahalomi |first17=Daniel |journal=The Astronomical Journal |volume=160 |issue=4 |page=155 |bibcode=2020AJ....160..155W |s2cid=212717799 |doi-access=free }}</ref>

<ref name=Turner2021>{{citation|arxiv=2112.09621|year=2022|title=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|doi=10.3847/1538-3881/ac686f |last1=Turner |first1=Jake D. |last2=Flagg |first2=Laura |last3=Ridden-Harper |first3=Andrew |last4=Jayawardhana |first4=Ray |journal=The Astronomical Journal |volume=163 |issue=6 |page=281 |bibcode=2022AJ....163..281T |s2cid=245329747 |doi-access=free }}</ref>

}}

==Further reading==
* {{cite journal | title=No Transit Timing Variations in Wasp-4 | last1=Petrucci | first1=R. | last2=Jofré | first2=E. | last3=Schwartz | first3=M. | last4=Cúneo | first4=V. | last5=Martínez | first5=C. | last6=Gómez | first6=M. | last7=Buccino | first7=A. P. | last8=Mauas | first8=P. J. D. | display-authors=1 | journal=The Astrophysical Journal Letters | volume=779 | issue=2 | at=L23 | year=2013 | arxiv=1311.2048 | bibcode=2013ApJ...779L..23P | bibcode-access=free | doi=10.1088/2041-8205/779/2/L23 | doi-access=free | s2cid=118376692 }}
* {{cite journal | title=Gemini/GMOS Transmission Spectral Survey: Complete Optical Transmission Spectrum of the Hot Jupiter WASP-4b | last1=Huitson | first1=C. M. | last2=Désert | first2=J.-M. | last3=Bean | first3=J. L. | last4=Fortney | first4=J. J. | last5=Stevenson | first5=K. B. | last6=Bergmann | first6=M. | display-authors=1 | journal=The Astronomical Journal | volume=154 | issue=3 | at=95 | year=2017 | arxiv=1707.06575 | bibcode=2017AJ....154...95H | bibcode-access=free | doi=10.3847/1538-3881/aa7f72 | doi-access=free | s2cid=119415111 }}
* {{cite journal |last1=Bouma |first1=L. G. |last2=Winn |first2=J. N. |display-authors=etal |date=June 2019 |title=WASP-4b Arrived Early for the TESS Mission |journal=[[The Astronomical Journal]] |volume=157 |issue=6 |pages=217 |doi=10.3847/1538-3881/ab189f |arxiv=1903.02573 |bibcode=2019AJ....157..217B |doi-access=free }}

==External links==
{{commonscat-inline|WASP-4 b|WASP-4b}}
* {{cite web | url=https://wasp-planets.net/ | title=Transiting exoplanets from the Wide Angle Search for Planets | website=WASP Planets | publisher=Coel Hellier | access-date=2020-12-27 }}
* {{cite web |url=http://www.superwasp.org/press_release2/WASP2007_national_pressV5.pdf |archive-url=https://web.archive.org/web/20080516083642/http://www.superwasp.org/press_release2/WASP2007_national_pressV5.pdf |url-status=dead |archive-date=2008-05-16 |title=UK planet hunters announce three new finds |access-date=2008-07-02 |date=2007-10-30 }}

{{Sky|23|34|15.06|-|42|03|41.1|1000}}
{{Phoenix (constellation)}}

[[Category:Exoplanets discovered by WASP]]
[[Category:Exoplanets discovered in 2007]]
[[Category:Giant planets]]
[[Category:Hot Jupiters]]
[[Category:Transiting exoplanets]]
[[Category:Phoenix (constellation)]]