WASP-139 b
WASP-139 b is a hot Jupiter orbiting the K0 star WASP-139 in the constellation Eridanus. It lies about 693 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is WASP-139 b?
WASP-139 b has a radius of 8.97 times that of Earth, or 0.80 times the radius of Jupiter. Its mass is 37.2 times that of Earth, giving it a density of 0.31 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is WASP-139 b in the Habitable Zone?
WASP-139 b orbits inside the inner edge of the habitable zone of WASP-139. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of WASP-139: 0.521–1.245 AU (conservative: 0.660–1.180 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on WASP-139 b
The equilibrium temperature of WASP-139 b is about 910 K (637 °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-139 b — one full orbit around WASP-139 — lasts 5.92 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.062 AU — closer to its star than Mercury is to the Sun.
How Was WASP-139 b Discovered?
WASP-139 b was discovered in 2016 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-139 b?
WASP-139 b is 693.0 light-years (212.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1333. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 12,196,800 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-139 b scores 0.10, ranking #4,409 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: WASP-139
WASP-139 b belongs to a system of 2 stars; it orbits WASP-139.
WASP-139
- Spectral type
- K0
- Surface temperature
- 5,310 K (Sun: 5,772 K)
- Mass
- 0.92 M☉
- Radius
- 0.80 R☉
- Age
- 0.5 billion years (Sun: 4.6)
Planetary System
WASP-139 b is the only planet known to orbit WASP-139 so far.
WASP-139 b — Complete Data
| Radius | 8.967 Earth radii (0.800 Jupiter radii) |
|---|---|
| Mass | 37.19 Earth masses (0.117 Jupiter masses) |
| Density | 0.31 g/cm³ (Earth: 5.51) |
| Orbital period | 5.92 days |
| Orbital distance | 0.062 AU |
| Equilibrium temperature | 910 K (637 °C) |
| Earth Similarity Index | 0.10 |
| Distance from Earth | 693.0 light-years (212.5 parsecs) |
| Constellation | Eridanus |
| Discovery method | Transit |
| Discovery facility | SuperWASP-South |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-11-30. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About WASP-139 b
Is WASP-139 b habitable?
No — WASP-139 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is WASP-139 b?
WASP-139 b is about 693 light-years from Earth in the constellation Eridanus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 12,196,800 years to get there.
How big is WASP-139 b compared to Earth?
WASP-139 b has 8.97 times the radius of Earth and about 37.2 times its mass.
How long is a year on WASP-139 b?
One orbit around WASP-139 takes 5.9 Earth days — short enough that 62 of its years would fit into one Earth year.
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