HATS-15 b
HATS-15 b is a hot Jupiter orbiting the G9 V star HATS-15 in the constellation Capricornus. It lies about 3,717 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is HATS-15 b?
HATS-15 b has a radius of 12.39 times that of Earth, or 1.11 times the radius of Jupiter. Its mass is 690 times that of Earth, giving it a density of 1.97 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HATS-15 b in the Habitable Zone?
HATS-15 b orbits inside the inner edge of the habitable zone of HATS-15. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HATS-15: 0.609–1.457 AU (conservative: 0.772–1.381 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HATS-15 b
The equilibrium temperature of HATS-15 b is about 1,505 K (1,232 °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-15 b — one full orbit around HATS-15 — lasts just 41.9 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.027 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.13).
How Was HATS-15 b Discovered?
HATS-15 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-15 b?
HATS-15 b is 3,716.7 light-years (1,139.6 parsecs) from Earth. Light arriving here tonight left the planet about 3,717 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 65,413,920 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-15 b scores 0.07, ranking #4,861 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HATS-15
HATS-15
- Spectral type
- G9 V
- Surface temperature
- 5,311 K (Sun: 5,772 K)
- Mass
- 0.87 M☉
- Radius
- 0.92 R☉
- Luminosity
- 0.6250 L☉
- Age
- 11.0 billion years (Sun: 4.6)
Planetary System
HATS-15 b is the only planet known to orbit HATS-15 so far.
HATS-15 b — Complete Data
| Radius | 12.386 Earth radii (1.105 Jupiter radii) |
|---|---|
| Mass | 689.69 Earth masses (2.170 Jupiter masses) |
| Density | 1.97 g/cm³ (Earth: 5.51) |
| Orbital period | 1.75 days |
| Orbital distance | 0.027 AU |
| Eccentricity | 0.126 |
| Equilibrium temperature | 1,505 K (1,232 °C) |
| Earth Similarity Index | 0.07 |
| Distance from Earth | 3,716.7 light-years (1,139.6 parsecs) |
| Constellation | Capricornus |
| Discovery method | Transit |
| Discovery facility | HATSouth |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-06-22. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HATS-15 b
Is HATS-15 b habitable?
No — HATS-15 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HATS-15 b?
HATS-15 b is about 3,717 light-years from Earth in the constellation Capricornus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 65,413,920 years to get there.
How big is HATS-15 b compared to Earth?
HATS-15 b has 12.39 times the radius of Earth and about 690 times its mass.
How long is a year on HATS-15 b?
One orbit around HATS-15 takes 1.7 Earth days — short enough that 209 of its years would fit into one Earth year.
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