HATS-77 b
HATS-77 b is a hot Jupiter orbiting HATS-77 in the constellation Antlia. It lies about 1,423 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is HATS-77 b?
HATS-77 b has a radius of 13.06 times that of Earth, or 1.17 times the radius of Jupiter. Its mass is 437 times that of Earth, giving it a density of 1.08 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HATS-77 b in the Habitable Zone?
HATS-77 b orbits inside the inner edge of the habitable zone of HATS-77. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HATS-77: 0.258–0.652 AU (conservative: 0.327–0.618 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HATS-77 b
The equilibrium temperature of HATS-77 b is about 828 K (555 °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 78.37 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HATS-77 b — one full orbit around HATS-77 — lasts 3.09 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.036 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.045).
How Was HATS-77 b Discovered?
HATS-77 b was discovered in 2021 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-77 b?
HATS-77 b is 1,422.6 light-years (436.2 parsecs) from Earth. Light arriving here tonight left the planet about 1,423 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 25,037,760 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. HATS-77 b scores 0.08, ranking #4,626 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HATS-77
HATS-77
- Surface temperature
- 4,071 K (Sun: 5,772 K)
- Mass
- 0.66 M☉
- Radius
- 0.64 R☉
- Luminosity
- 0.1019 L☉
- Age
- 12.1 billion years (Sun: 4.6)
Planetary System
HATS-77 b is the only planet known to orbit HATS-77 so far.
HATS-77 b — Complete Data
| Radius | 13.058 Earth radii (1.165 Jupiter radii) |
|---|---|
| Mass | 436.70 Earth masses (1.374 Jupiter masses) |
| Density | 1.08 g/cm³ (Earth: 5.51) |
| Orbital period | 3.09 days |
| Orbital distance | 0.036 AU |
| Eccentricity | 0.045 |
| Equilibrium temperature | 828 K (555 °C) |
| Stellar irradiation | 78.37× Earth |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 1,422.6 light-years (436.2 parsecs) |
| Constellation | Antlia |
| Discovery method | Transit |
| Discovery facility | HATSouth |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-12-13. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HATS-77 b
Is HATS-77 b habitable?
No — HATS-77 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HATS-77 b?
HATS-77 b is about 1,423 light-years from Earth in the constellation Antlia. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 25,037,760 years to get there.
How big is HATS-77 b compared to Earth?
HATS-77 b has 13.06 times the radius of Earth and about 437 times its mass.
How long is a year on HATS-77 b?
One orbit around HATS-77 takes 3.1 Earth days — short enough that 118 of its years would fit into one Earth year.
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