GJ 3021 b
GJ 3021 b is a cold gas giant orbiting the G6 V star GJ 3021 in the constellation Hydrus. It lies about 57 light-years from Earth and was discovered in 2000 using the radial velocity method.
Is GJ 3021 b in the Habitable Zone?
GJ 3021 b orbits inside the inner edge of the habitable zone of GJ 3021. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 3021: 0.619–1.467 AU (conservative: 0.784–1.391 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 3021 b
The equilibrium temperature of GJ 3021 b is about 350 K (77 °C) — hotter than anywhere on Earth. 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 GJ 3021 b — one full orbit around GJ 3021 — lasts 133.7 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.490 AU — comparable to the inner Solar System. Its orbit is highly elliptical (eccentricity 0.51), swinging dramatically closer to and farther from its star.
How Was GJ 3021 b Discovered?
GJ 3021 b was discovered in 2000 using the radial velocity method, with observations from La Silla 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 GJ 3021 b?
GJ 3021 b is 57.3 light-years (17.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1969. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,008,480 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. GJ 3021 b scores 0.29, ranking #1,895 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 3021
GJ 3021 b belongs to a system of 2 stars; it orbits GJ 3021.
GJ 3021
- Spectral type
- G6 V
- Surface temperature
- 5,540 K (Sun: 5,772 K)
- Mass
- 0.90 M☉
- Radius
- 0.90 R☉
- Luminosity
- 0.6607 L☉
Planetary System
GJ 3021 b is the only planet known to orbit GJ 3021 so far.
GJ 3021 b — Complete Data
| Mass (best estimate) | 1,071.04 Earth masses |
|---|---|
| Orbital period | 133.71 days |
| Orbital distance | 0.490 AU |
| Eccentricity | 0.511 |
| Equilibrium temperature | 350 K (77 °C) |
| Earth Similarity Index | 0.29 |
| Distance from Earth | 57.3 light-years (17.6 parsecs) |
| Constellation | Hydrus |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2000 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 3021 b
Is GJ 3021 b habitable?
No — GJ 3021 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 3021 b?
GJ 3021 b is about 57 light-years from Earth in the constellation Hydrus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,008,480 years to get there.
How long is a year on GJ 3021 b?
One orbit around GJ 3021 takes 133.7 Earth days.
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