GPX-1 b
GPX-1 b is a hot Jupiter orbiting the F2 star GPX-1 in the constellation Perseus. It lies about 2,136 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is GPX-1 b?
GPX-1 b has a radius of 16.48 times that of Earth, or 1.47 times the radius of Jupiter. Its mass is 6,261 times that of Earth, giving it a density of 8.22 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is GPX-1 b in the Habitable Zone?
GPX-1 b orbits inside the inner edge of the habitable zone of GPX-1. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GPX-1: 1.615–3.727 AU (conservative: 2.046–3.534 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GPX-1 b
The equilibrium temperature of GPX-1 b is about 2,300 K (2,027 °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 4,650 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on GPX-1 b — one full orbit around GPX-1 — lasts just 41.9 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.034 AU — closer to its star than Mercury is to the Sun.
How Was GPX-1 b Discovered?
GPX-1 b was discovered in 2021 using the transit method, with observations from Acton Sky Portal Observatory.
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 GPX-1 b?
GPX-1 b is 2,136.4 light-years (655.0 parsecs) from Earth. Light arriving here tonight left the planet about 2,136 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 37,600,640 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. GPX-1 b scores 0.06, ranking #5,223 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GPX-1
GPX-1
- Spectral type
- F2
- Surface temperature
- 7,000 K (Sun: 5,772 K)
- Mass
- 1.68 M☉
- Radius
- 1.56 R☉
- Luminosity
- 5.3300 L☉
- Age
- 0.3 billion years (Sun: 4.6)
Planetary System
GPX-1 b is the only planet known to orbit GPX-1 so far.
GPX-1 b — Complete Data
| Radius | 16.477 Earth radii (1.470 Jupiter radii) |
|---|---|
| Mass | 6,261.22 Earth masses (19.700 Jupiter masses) |
| Density | 8.22 g/cm³ (Earth: 5.51) |
| Orbital period | 1.74 days |
| Orbital distance | 0.034 AU |
| Equilibrium temperature | 2,300 K (2,027 °C) |
| Stellar irradiation | 4,650.00× Earth |
| Earth Similarity Index | 0.06 |
| Distance from Earth | 2,136.4 light-years (655.0 parsecs) |
| Constellation | Perseus |
| Discovery method | Transit |
| Discovery facility | Acton Sky Portal Observatory |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-10-04. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GPX-1 b
Is GPX-1 b habitable?
No — GPX-1 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GPX-1 b?
GPX-1 b is about 2,136 light-years from Earth in the constellation Perseus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 37,600,640 years to get there.
How big is GPX-1 b compared to Earth?
GPX-1 b has 16.48 times the radius of Earth and about 6,261 times its mass.
How long is a year on GPX-1 b?
One orbit around GPX-1 takes 1.7 Earth days — short enough that 209 of its years would fit into one Earth year.
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