WASP-4 b
WASP-4 b is a hot Jupiter orbiting WASP-4 in the constellation Phoenix. It lies about 872 light-years from Earth and was discovered in 2007 using the transit method.
How Big Is WASP-4 b?
WASP-4 b has a radius of 15.12 times that of Earth, or 1.35 times the radius of Jupiter. Its mass is 381 times that of Earth, giving it a density of 0.65 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is WASP-4 b in the Habitable Zone?
The position of WASP-4 b relative to the habitable zone of WASP-4 cannot be precisely determined from the available orbital data.
Temperature on WASP-4 b
The equilibrium temperature of WASP-4 b is about 1,653 K (1,380 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on WASP-4 b — one full orbit around WASP-4 — lasts just 32.1 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.023 AU — closer to its star than Mercury is to the Sun.
How Was WASP-4 b Discovered?
WASP-4 b was discovered in 2007 using the transit method, with observations from SuperWASP.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is WASP-4 b?
WASP-4 b is 871.5 light-years (267.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1155. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 15,338,400 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. WASP-4 b scores 0.06, ranking #5,120 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: WASP-4
WASP-4
- Mass
- 0.90 M☉
- Radius
- 0.91 R☉
Planetary System
WASP-4 b is the only planet known to orbit WASP-4 so far.
WASP-4 b — Complete Data
| Radius | 15.121 Earth radii (1.349 Jupiter radii) |
|---|---|
| Mass | 381.39 Earth masses (1.200 Jupiter masses) |
| Density | 0.65 g/cm³ (Earth: 5.51) |
| Orbital period | 1.34 days |
| Orbital distance | 0.023 AU |
| Equilibrium temperature | 1,653 K (1,380 °C) |
| Earth Similarity Index | 0.06 |
| Distance from Earth | 871.5 light-years (267.2 parsecs) |
| Constellation | Phoenix |
| Discovery method | Transit |
| Discovery facility | SuperWASP |
| Discovery year | 2007 |
Data: NASA Exoplanet Archive, last updated 2025-08-28. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About WASP-4 b
Is WASP-4 b habitable?
WASP-4 b is not known to orbit within the habitable zone of WASP-4, and as a hot Jupiter it is an unlikely candidate for life as we know it.
How far away is WASP-4 b?
WASP-4 b is about 872 light-years from Earth in the constellation Phoenix. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 15,338,400 years to get there.
How big is WASP-4 b compared to Earth?
WASP-4 b has 15.12 times the radius of Earth and about 381 times its mass.
How long is a year on WASP-4 b?
One orbit around WASP-4 takes 1.3 Earth days — short enough that 273 of its years would fit into one Earth year.
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