WASP-4b is an
exoplanet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...
, specifically a
hot Jupiter
Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter (i.e. Jupiter analogue, Jupiter analogues) but that have very short orbital periods (). The close proximity to t ...
, approximately 891
light-year
A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
s away
in the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The first constellati ...
of
Phoenix.
Discovery
The planet was the discovered by the
Wide Angle Search for Planets
WASP or Wide Angle Search for Planets is an international consortium of several academic organisations performing an ultra-wide angle search for exoplanets using transit photometry. The array of robotic telescopes aims to Astronomical survey, s ...
team using images taken with the SuperWASP-South project's eight wide-angle cameras located at the
South African Astronomical Observatory
The South African Astronomical Observatory (SAAO) is the national centre for optical and infrared astronomy in South Africa. It was established in 1972. The observatory is run by the National Research Foundation of South Africa. The facility's f ...
.
Analysis of over 4000 images taken between May and November 2006 resulted in the detection of a
transit
Transit may refer to:
Arts and entertainment Film
* ''Transit'' (1980 film), a 1980 Israeli film
* ''Transit'' (1986 film), a Canadian short film
* ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countrie ...
occurring every 1.3 days. Follow-up
radial velocity
The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...
observations using the
Swiss 1.2-metre Leonhard Euler Telescope confirmed that the transiting object was a planet.
Characteristics
The
planetary equilibrium temperature
The planetary equilibrium temperature is a theoretical temperature that a planet would be if it were in radiative equilibrium, typically under the assumption that it radiates as a black body being heated only by its parent star. In this model, th ...
would be 1650 K,
but the measured dayside temperature is higher, with a 2015 study finding 1900 K
[ and a 2020 study finding 1957 K.][
A study in 2012, utilizing the ]Rossiter–McLaughlin effect
The Rossiter–McLaughlin effect is a spectroscopic phenomenon observed when an object moves across the face of a rotating star. The star is seen to undergo a redshift anomaly caused by the obscuration of different parts of its disk.
Descriptio ...
, determined the planetary orbit is probably aligned with the equatorial plane of the star, with misalignment equal to -1°.[ The orbital decay was confirmed in 2025. It is primarily driven by tidal interactions between the planet and its host star.]
References
Further reading
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External links
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{{Phoenix (constellation)
Exoplanets discovered by WASP
Exoplanets discovered in 2007
Giant planets
Hot Jupiters
Transiting exoplanets
Phoenix (constellation)