HATS-8 b
HATS-8 b is a hot Jupiter orbiting HATS-8 in the constellation Sagittarius. It lies about 2,592 light-years from Earth and was discovered in 2015 using the transit method.
How Big Is HATS-8 b?
HATS-8 b has a radius of 9.79 times that of Earth, or 0.87 times the radius of Jupiter. Its mass is 43.9 times that of Earth, giving it a density of 0.26 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HATS-8 b in the Habitable Zone?
HATS-8 b orbits inside the inner edge of the habitable zone of HATS-8. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HATS-8: 0.792–1.871 AU (conservative: 1.003–1.774 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HATS-8 b
The equilibrium temperature of HATS-8 b is about 1,324 K (1,051 °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-8 b — one full orbit around HATS-8 — lasts 3.58 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.047 AU — closer to its star than Mercury is to the Sun. Its orbit is highly elliptical (eccentricity 0.38), swinging dramatically closer to and farther from its star.
How Was HATS-8 b Discovered?
HATS-8 b was discovered in 2015 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-8 b?
HATS-8 b is 2,591.8 light-years (794.6 parsecs) from Earth. Light arriving here tonight left the planet about 2,592 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 45,615,680 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-8 b scores 0.09, ranking #4,517 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HATS-8
HATS-8
- Surface temperature
- 5,679 K (Sun: 5,772 K)
- Mass
- 1.06 M☉
- Radius
- 1.09 R☉
- Age
- 5.1 billion years (Sun: 4.6)
Planetary System
HATS-8 b is the only planet known to orbit HATS-8 so far.
HATS-8 b — Complete Data
| Radius | 9.785 Earth radii (0.873 Jupiter radii) |
|---|---|
| Mass | 43.86 Earth masses (0.138 Jupiter masses) |
| Density | 0.26 g/cm³ (Earth: 5.51) |
| Orbital period | 3.58 days |
| Orbital distance | 0.047 AU |
| Eccentricity | 0.376 |
| Equilibrium temperature | 1,324 K (1,051 °C) |
| Earth Similarity Index | 0.09 |
| Distance from Earth | 2,591.8 light-years (794.6 parsecs) |
| Constellation | Sagittarius |
| Discovery method | Transit |
| Discovery facility | HATSouth |
| Discovery year | 2015 |
Data: NASA Exoplanet Archive, last updated 2015-06-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HATS-8 b
Is HATS-8 b habitable?
No — HATS-8 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HATS-8 b?
HATS-8 b is about 2,592 light-years from Earth in the constellation Sagittarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 45,615,680 years to get there.
How big is HATS-8 b compared to Earth?
HATS-8 b has 9.79 times the radius of Earth and about 43.9 times its mass.
How long is a year on HATS-8 b?
One orbit around HATS-8 takes 3.6 Earth days — short enough that 102 of its years would fit into one Earth year.
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