WASP-172 b
WASP-172 b is a hot Jupiter orbiting the F1 V star WASP-172 in the constellation Centaurus. It lies about 1,755 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is WASP-172 b?
WASP-172 b has a radius of 17.60 times that of Earth, or 1.57 times the radius of Jupiter. Its mass is 149 times that of Earth, giving it a density of 0.16 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is WASP-172 b in the Habitable Zone?
WASP-172 b orbits inside the inner edge of the habitable zone of WASP-172. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of WASP-172: 1.915–4.423 AU (conservative: 2.425–4.194 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on WASP-172 b
The equilibrium temperature of WASP-172 b is about 1,740 K (1,467 °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-172 b — one full orbit around WASP-172 — lasts 5.48 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.069 AU — closer to its star than Mercury is to the Sun.
How Was WASP-172 b Discovered?
WASP-172 b was discovered in 2018 using the transit method, with observations from SuperWASP-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-172 b?
WASP-172 b is 1,755.1 light-years (538.1 parsecs) from Earth. Light arriving here tonight left the planet about 1,755 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 30,889,760 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-172 b scores 0.05, ranking #5,254 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: WASP-172
WASP-172
- Spectral type
- F1 V
- Surface temperature
- 6,900 K (Sun: 5,772 K)
- Mass
- 1.49 M☉
- Radius
- 1.91 R☉
- Age
- 1.8 billion years (Sun: 4.6)
Planetary System
WASP-172 b is the only planet known to orbit WASP-172 so far.
WASP-172 b — Complete Data
| Radius | 17.598 Earth radii (1.570 Jupiter radii) |
|---|---|
| Mass | 149.38 Earth masses (0.470 Jupiter masses) |
| Density | 0.16 g/cm³ (Earth: 5.51) |
| Orbital period | 5.48 days |
| Orbital distance | 0.069 AU |
| Equilibrium temperature | 1,740 K (1,467 °C) |
| Earth Similarity Index | 0.05 |
| Distance from Earth | 1,755.1 light-years (538.1 parsecs) |
| Constellation | Centaurus |
| Discovery method | Transit |
| Discovery facility | SuperWASP-South |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2018-10-24. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About WASP-172 b
Is WASP-172 b habitable?
No — WASP-172 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is WASP-172 b?
WASP-172 b is about 1,755 light-years from Earth in the constellation Centaurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 30,889,760 years to get there.
How big is WASP-172 b compared to Earth?
WASP-172 b has 17.60 times the radius of Earth and about 149 times its mass.
How long is a year on WASP-172 b?
One orbit around WASP-172 takes 5.5 Earth days — short enough that 67 of its years would fit into one Earth year.
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