HATS-17 b
HATS-17 b is a cold gas giant orbiting the G V star HATS-17 in the constellation Centaurus. It lies about 1,306 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is HATS-17 b?
HATS-17 b has a radius of 8.71 times that of Earth, or 0.78 times the radius of Jupiter. Its mass is 425 times that of Earth, giving it a density of 3.50 g/cm³ — between that of rocky and gaseous planets.
Is HATS-17 b in the Habitable Zone?
HATS-17 b orbits inside the inner edge of the habitable zone of HATS-17. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HATS-17: 0.832–1.957 AU (conservative: 1.054–1.856 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HATS-17 b
The equilibrium temperature of HATS-17 b is about 814 K (541 °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 72.70 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HATS-17 b — one full orbit around HATS-17 — lasts 16.3 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.131 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.029).
How Was HATS-17 b Discovered?
HATS-17 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-17 b?
HATS-17 b is 1,305.7 light-years (400.3 parsecs) from Earth. Light arriving here tonight left the planet about 1,306 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 22,980,320 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-17 b scores 0.11, ranking #4,367 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HATS-17
HATS-17
- Spectral type
- G V
- Surface temperature
- 5,846 K (Sun: 5,772 K)
- Mass
- 1.13 M☉
- Radius
- 1.09 R☉
- Luminosity
- 1.2400 L☉
- Age
- 2.1 billion years (Sun: 4.6)
Planetary System
HATS-17 b is the only planet known to orbit HATS-17 so far.
HATS-17 b — Complete Data
| Radius | 8.709 Earth radii (0.777 Jupiter radii) |
|---|---|
| Mass | 425.26 Earth masses (1.338 Jupiter masses) |
| Density | 3.50 g/cm³ (Earth: 5.51) |
| Orbital period | 16.25 days |
| Orbital distance | 0.131 AU |
| Eccentricity | 0.029 |
| Equilibrium temperature | 814 K (541 °C) |
| Stellar irradiation | 72.70× Earth |
| Earth Similarity Index | 0.11 |
| Distance from Earth | 1,305.7 light-years (400.3 parsecs) |
| Constellation | Centaurus |
| Discovery method | Transit |
| Discovery facility | HATSouth |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-09-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HATS-17 b
Is HATS-17 b habitable?
No — HATS-17 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HATS-17 b?
HATS-17 b is about 1,306 light-years from Earth in the constellation Centaurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 22,980,320 years to get there.
How big is HATS-17 b compared to Earth?
HATS-17 b has 8.71 times the radius of Earth and about 425 times its mass.
How long is a year on HATS-17 b?
One orbit around HATS-17 takes 16.3 Earth days — short enough that 22 of its years would fit into one Earth year.
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