HATS-31 b
HATS-31 b is a hot Jupiter orbiting HATS-31 in the constellation Hydra. It lies about 2,524 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is HATS-31 b?
HATS-31 b has a radius of 18.38 times that of Earth, or 1.64 times the radius of Jupiter. Its mass is 280 times that of Earth, giving it a density of 0.24 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HATS-31 b in the Habitable Zone?
HATS-31 b orbits inside the inner edge of the habitable zone of HATS-31. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HATS-31: 1.506–3.524 AU (conservative: 1.907–3.341 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HATS-31 b
The equilibrium temperature of HATS-31 b is about 1,823 K (1,550 °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 HATS-31 b — one full orbit around HATS-31 — lasts 3.38 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.048 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.23).
How Was HATS-31 b Discovered?
HATS-31 b was discovered in 2016 using the transit method, with observations from HATSouth.
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 HATS-31 b?
HATS-31 b is 2,524.4 light-years (774.0 parsecs) from Earth. Light arriving here tonight left the planet about 2,524 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 44,429,440 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. HATS-31 b scores 0.05, ranking #5,280 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HATS-31
HATS-31
- Surface temperature
- 6,050 K (Sun: 5,772 K)
- Mass
- 1.27 M☉
- Radius
- 1.87 R☉
- Luminosity
- 4.1600 L☉
- Age
- 4.3 billion years (Sun: 4.6)
Planetary System
HATS-31 b is the only planet known to orbit HATS-31 so far.
HATS-31 b — Complete Data
| Radius | 18.383 Earth radii (1.640 Jupiter radii) |
|---|---|
| Mass | 279.69 Earth masses (0.880 Jupiter masses) |
| Density | 0.24 g/cm³ (Earth: 5.51) |
| Orbital period | 3.38 days |
| Orbital distance | 0.048 AU |
| Eccentricity | 0.233 |
| Equilibrium temperature | 1,823 K (1,550 °C) |
| Earth Similarity Index | 0.05 |
| Distance from Earth | 2,524.4 light-years (774.0 parsecs) |
| Constellation | Hydra |
| Discovery method | Transit |
| Discovery facility | HATSouth |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-11-30. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HATS-31 b
Is HATS-31 b habitable?
No — HATS-31 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HATS-31 b?
HATS-31 b is about 2,524 light-years from Earth in the constellation Hydra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 44,429,440 years to get there.
How big is HATS-31 b compared to Earth?
HATS-31 b has 18.38 times the radius of Earth and about 280 times its mass.
How long is a year on HATS-31 b?
One orbit around HATS-31 takes 3.4 Earth days — short enough that 108 of its years would fit into one Earth year.
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