WASP-166 b
WASP-166 b is a hot Jupiter orbiting the F9 V star WASP-166 in the constellation Hydra. It lies about 372 light-years from Earth and was discovered in 2019 using the transit method.
How Big Is WASP-166 b?
WASP-166 b has a radius of 7.06 times that of Earth, or 0.63 times the radius of Jupiter. Its mass is 32.1 times that of Earth, giving it a density of 0.54 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is WASP-166 b in the Habitable Zone?
WASP-166 b orbits inside the inner edge of the habitable zone of WASP-166. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of WASP-166: 0.987–2.311 AU (conservative: 1.251–2.191 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on WASP-166 b
The equilibrium temperature of WASP-166 b is about 1,270 K (997 °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 440 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on WASP-166 b — one full orbit around WASP-166 — lasts 5.44 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.064 AU — closer to its star than Mercury is to the Sun.
How Was WASP-166 b Discovered?
WASP-166 b was discovered in 2019 using the transit method, with observations from WASP-South.
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-166 b?
WASP-166 b is 372.4 light-years (114.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1654. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,554,240 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-166 b scores 0.12, ranking #4,339 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: WASP-166
WASP-166
- Spectral type
- F9 V
- Surface temperature
- 6,050 K (Sun: 5,772 K)
- Mass
- 1.19 M☉
- Radius
- 1.22 R☉
- Age
- 2.1 billion years (Sun: 4.6)
Planetary System
WASP-166 b is the only planet known to orbit WASP-166 so far.
WASP-166 b — Complete Data
| Radius | 7.062 Earth radii (0.630 Jupiter radii) |
|---|---|
| Mass | 32.10 Earth masses (0.101 Jupiter masses) |
| Density | 0.54 g/cm³ (Earth: 5.51) |
| Orbital period | 5.44 days |
| Orbital distance | 0.064 AU |
| Equilibrium temperature | 1,270 K (997 °C) |
| Stellar irradiation | 440.00× Earth |
| Earth Similarity Index | 0.12 |
| Distance from Earth | 372.4 light-years (114.2 parsecs) |
| Constellation | Hydra |
| Discovery method | Transit |
| Discovery facility | WASP-South |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2019-07-19. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About WASP-166 b
Is WASP-166 b habitable?
No — WASP-166 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is WASP-166 b?
WASP-166 b is about 372 light-years from Earth in the constellation Hydra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,554,240 years to get there.
How big is WASP-166 b compared to Earth?
WASP-166 b has 7.06 times the radius of Earth and about 32.1 times its mass.
How long is a year on WASP-166 b?
One orbit around WASP-166 takes 5.4 Earth days — short enough that 67 of its years would fit into one Earth year.
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