HATS-18 b
HATS-18 b is a hot Jupiter orbiting HATS-18 in the constellation Hydra. It lies about 2,036 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is HATS-18 b?
HATS-18 b has a radius of 14.90 times that of Earth, or 1.33 times the radius of Jupiter. Its mass is 629 times that of Earth, giving it a density of 1.12 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HATS-18 b in the Habitable Zone?
HATS-18 b orbits inside the inner edge of the habitable zone of HATS-18. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HATS-18: 0.727–1.721 AU (conservative: 0.920–1.631 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HATS-18 b
The equilibrium temperature of HATS-18 b is about 2,069 K (1,796 °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-18 b — one full orbit around HATS-18 — lasts just 20.1 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.017 AU — closer to its star than Mercury is to the Sun.
How Was HATS-18 b Discovered?
HATS-18 b was discovered in 2016 using the transit method, with observations from Multiple Observatories.
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-18 b?
HATS-18 b is 2,036.4 light-years (624.4 parsecs) from Earth. Light arriving here tonight left the planet about 2,036 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 35,840,640 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-18 b scores 0.06, ranking #5,131 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HATS-18
HATS-18
- Surface temperature
- 5,600 K (Sun: 5,772 K)
- Mass
- 1.04 M☉
- Radius
- 1.02 R☉
Planetary System
HATS-18 b is the only planet known to orbit HATS-18 so far.
HATS-18 b — Complete Data
| Radius | 14.897 Earth radii (1.329 Jupiter radii) |
|---|---|
| Mass | 629.14 Earth masses (1.980 Jupiter masses) |
| Density | 1.12 g/cm³ (Earth: 5.51) |
| Orbital period | 0.84 days |
| Orbital distance | 0.017 AU |
| Equilibrium temperature | 2,069 K (1,796 °C) |
| Earth Similarity Index | 0.06 |
| Distance from Earth | 2,036.4 light-years (624.4 parsecs) |
| Constellation | Hydra |
| Discovery method | Transit |
| Discovery facility | Multiple Observatories |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2019-07-08. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HATS-18 b
Is HATS-18 b habitable?
No — HATS-18 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HATS-18 b?
HATS-18 b is about 2,036 light-years from Earth in the constellation Hydra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 35,840,640 years to get there.
How big is HATS-18 b compared to Earth?
HATS-18 b has 14.90 times the radius of Earth and about 629 times its mass.
How long is a year on HATS-18 b?
One orbit around HATS-18 takes 0.8 Earth days — short enough that 436 of its years would fit into one Earth year.
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