WASP-4b is an extrasolar planet

Extrasolar planet

An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...

 approximately 1,000 light-year

Light-year

A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

s away in the constellation

Constellation

In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 of Phoenix

Phoenix (constellation)

Phoenix is a minor constellation in the southern sky. It is named after the Phoenix, a mythical bird. It is faint: there are only two stars in the whole constellation which are brighter than magnitude 5.0...

. The planet was discovered orbiting the star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 WASP-4

WASP-4

WASP-4 is a G-type main sequence star approximately 1,000 light-years away in the constellation of Phoenix.-Planetary system:In 2007, an extrasolar planet, WASP-4b, was discovered orbiting this star....

 in October 2007. The planet's mass and radius indicate that it is a gas giant

Gas giant

A gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in the Solar System: Jupiter, Saturn, Uranus, and Neptune...

, similar to Jupiter

Jupiter

Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

. WASP-4b is close enough to its star to be classified as a hot Jupiter

Hot Jupiter

Hot Jupiters are a class of extrasolar planet whose mass is close to or exceeds that of Jupiter...

 and has an atmospheric temperature of approximately 1650 K

Kelvin

The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...

.
The planet was the discovered by the SuperWASP

SuperWASP

SuperWASP is an international academic organisation performing an ultra-wide angle search for transiting extrasolar planets with the aim of covering the entire sky down to ~15th magnitude.-Equipment:...

 project using cameras in South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

. After its discovery, the mass of the WASP-4 b was determined by measuring the radial velocity of WASP-4, which confirmed that the object that caused the transit was a planet.