HS Psc b
HS Psc b is a hot Jupiter orbiting the K7 V star HS Psc in the constellation Pisces. It lies about 123 light-years from Earth and was discovered in 2024 using the radial velocity method.
Is HS Psc b in the Habitable Zone?
HS Psc b orbits inside the inner edge of the habitable zone of HS Psc. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HS Psc: 0.282–0.706 AU (conservative: 0.357–0.670 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Orbit and Year Length
A year on HS Psc b — one full orbit around HS Psc — lasts 3.99 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.044 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.27).
How Was HS Psc b Discovered?
HS Psc b was discovered in 2024 using the radial velocity method, with observations from McDonald Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is HS Psc b?
HS Psc b is 122.8 light-years (37.7 parsecs) from Earth. Light arriving here tonight left the planet around the year 1904. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,161,280 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. HS Psc b scores 0.08, ranking #4,628 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HS Psc
HS Psc
- Spectral type
- K7 V
- Surface temperature
- 4,203 K (Sun: 5,772 K)
- Mass
- 0.69 M☉
- Radius
- 0.65 R☉
- Luminosity
- 0.1220 L☉
- Age
- 0.1 billion years (Sun: 4.6)
Planetary System
HS Psc b is the only planet known to orbit HS Psc so far.
HS Psc b — Complete Data
| Mass (best estimate) | 464.03 Earth masses |
|---|---|
| Orbital period | 3.99 days |
| Orbital distance | 0.044 AU |
| Eccentricity | 0.270 |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 122.8 light-years (37.7 parsecs) |
| Constellation | Pisces |
| Discovery method | Radial Velocity |
| Discovery facility | McDonald Observatory |
| Discovery year | 2024 |
Data: NASA Exoplanet Archive, last updated 2024-03-12. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HS Psc b
Is HS Psc b habitable?
No — HS Psc b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HS Psc b?
HS Psc b is about 123 light-years from Earth in the constellation Pisces. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,161,280 years to get there.
How long is a year on HS Psc b?
One orbit around HS Psc takes 4.0 Earth days — short enough that 92 of its years would fit into one Earth year.
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