HATS-42 b
HATS-42 b is a hot Jupiter orbiting HATS-42 in the constellation Puppis. It lies about 2,611 light-years from Earth and was discovered in 2018 using the transit method.
How Big Is HATS-42 b?
HATS-42 b has a radius of 15.69 times that of Earth, or 1.40 times the radius of Jupiter. Its mass is 598 times that of Earth, giving it a density of 0.83 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HATS-42 b in the Habitable Zone?
HATS-42 b orbits inside the inner edge of the habitable zone of HATS-42. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HATS-42: 1.203–2.815 AU (conservative: 1.524–2.669 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HATS-42 b
The equilibrium temperature of HATS-42 b is about 1,856 K (1,583 °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-42 b — one full orbit around HATS-42 — lasts 2.29 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.037 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.23).
How Was HATS-42 b Discovered?
HATS-42 b was discovered in 2018 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-42 b?
HATS-42 b is 2,610.5 light-years (800.4 parsecs) from Earth. Light arriving here tonight left the planet about 2,611 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 45,944,800 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-42 b scores 0.06, ranking #5,177 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HATS-42
HATS-42
- Surface temperature
- 6,060 K (Sun: 5,772 K)
- Mass
- 1.27 M☉
- Radius
- 1.48 R☉
- Luminosity
- 2.6600 L☉
- Age
- 3.3 billion years (Sun: 4.6)
Planetary System
HATS-42 b is the only planet known to orbit HATS-42 so far.
HATS-42 b — Complete Data
| Radius | 15.693 Earth radii (1.400 Jupiter radii) |
|---|---|
| Mass | 597.52 Earth masses (1.880 Jupiter masses) |
| Density | 0.83 g/cm³ (Earth: 5.51) |
| Orbital period | 2.29 days |
| Orbital distance | 0.037 AU |
| Eccentricity | 0.229 |
| Equilibrium temperature | 1,856 K (1,583 °C) |
| Earth Similarity Index | 0.06 |
| Distance from Earth | 2,610.5 light-years (800.4 parsecs) |
| Constellation | Puppis |
| Discovery method | Transit |
| Discovery facility | HATSouth |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2018-04-09. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HATS-42 b
Is HATS-42 b habitable?
No — HATS-42 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HATS-42 b?
HATS-42 b is about 2,611 light-years from Earth in the constellation Puppis. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 45,944,800 years to get there.
How big is HATS-42 b compared to Earth?
HATS-42 b has 15.69 times the radius of Earth and about 598 times its mass.
How long is a year on HATS-42 b?
One orbit around HATS-42 takes 2.3 Earth days — short enough that 159 of its years would fit into one Earth year.
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