WASP-2 b
WASP-2 b is a hot Jupiter orbiting WASP-2 in the constellation Delphinus. It lies about 500 light-years from Earth and was discovered in 2007 using the transit method.
How Big Is WASP-2 b?
WASP-2 b has a radius of 12.12 times that of Earth, or 1.08 times the radius of Jupiter. Its mass is 296 times that of Earth, giving it a density of 0.91 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is WASP-2 b in the Habitable Zone?
WASP-2 b orbits inside the inner edge of the habitable zone of WASP-2. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of WASP-2: 0.541–1.299 AU (conservative: 0.685–1.232 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on WASP-2 b
The equilibrium temperature of WASP-2 b is about 1,311 K (1,038 °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. It receives 492 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on WASP-2 b — one full orbit around WASP-2 — lasts 2.15 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.031 AU — closer to its star than Mercury is to the Sun.
How Was WASP-2 b Discovered?
WASP-2 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-2 b?
WASP-2 b is 499.8 light-years (153.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1527. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 8,796,480 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-2 b scores 0.08, ranking #4,779 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: WASP-2
WASP-2 b belongs to a system of 2 stars; it orbits WASP-2.
WASP-2
- Surface temperature
- 5,180 K (Sun: 5,772 K)
- Mass
- 0.90 M☉
- Radius
- 0.87 R☉
- Luminosity
- 0.4860 L☉
Planetary System
WASP-2 b is the only planet known to orbit WASP-2 so far.
WASP-2 b — Complete Data
| Radius | 12.117 Earth radii (1.081 Jupiter radii) |
|---|---|
| Mass | 295.90 Earth masses (0.931 Jupiter masses) |
| Density | 0.91 g/cm³ (Earth: 5.51) |
| Orbital period | 2.15 days |
| Orbital distance | 0.031 AU |
| Equilibrium temperature | 1,311 K (1,038 °C) |
| Stellar irradiation | 492.00× Earth |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 499.8 light-years (153.2 parsecs) |
| Constellation | Delphinus |
| Discovery method | Transit |
| Discovery facility | SuperWASP |
| Discovery year | 2007 |
Data: NASA Exoplanet Archive, last updated 2019-09-23. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About WASP-2 b
Is WASP-2 b habitable?
No — WASP-2 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is WASP-2 b?
WASP-2 b is about 500 light-years from Earth in the constellation Delphinus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 8,796,480 years to get there.
How big is WASP-2 b compared to Earth?
WASP-2 b has 12.12 times the radius of Earth and about 296 times its mass.
How long is a year on WASP-2 b?
One orbit around WASP-2 takes 2.2 Earth days — short enough that 170 of its years would fit into one Earth year.
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