GJ 3929 b
GJ 3929 b is a terrestrial planet orbiting GJ 3929 in the constellation Corona Borealis. It lies about 52 light-years from Earth and was discovered in 2022 using the transit method.
How Big Is GJ 3929 b?
GJ 3929 b has a radius of 1.09 times that of Earth. Its mass is 1.8 times that of Earth, giving it a density of 7.30 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is GJ 3929 b in the Habitable Zone?
GJ 3929 b orbits inside the inner edge of the habitable zone of GJ 3929. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 3929: 0.086–0.223 AU (conservative: 0.108–0.212 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 3929 b
The equilibrium temperature of GJ 3929 b is about 568 K (295 °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. It receives 17.30 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on GJ 3929 b — one full orbit around GJ 3929 — lasts 2.62 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.025 AU — closer to its star than Mercury is to the Sun.
How Was GJ 3929 b Discovered?
GJ 3929 b was discovered in 2022 using the transit method, with observations from Transiting Exoplanet Survey Satellite (TESS).
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 GJ 3929 b?
GJ 3929 b is 51.6 light-years (15.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1975. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 908,160 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 3929 b scores 0.37, ranking #627 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 3929
GJ 3929
- Surface temperature
- 3,384 K (Sun: 5,772 K)
- Mass
- 0.31 M☉
- Radius
- 0.32 R☉
- Luminosity
- 0.0109 L☉
- Age
- 7.1 billion years (Sun: 4.6)
The GJ 3929 Planetary System
GJ 3929 b is one of 2 known planets in the GJ 3929 system. Its siblings:
- GJ 3929 c (Super Earth)
GJ 3929 b — Complete Data
| Radius | 1.090 Earth radii (0.097 Jupiter radii) |
|---|---|
| Mass | 1.75 Earth masses (0.006 Jupiter masses) |
| Density | 7.30 g/cm³ (Earth: 5.51) |
| Orbital period | 2.62 days |
| Orbital distance | 0.025 AU |
| Equilibrium temperature | 568 K (295 °C) |
| Stellar irradiation | 17.30× Earth |
| Earth Similarity Index | 0.37 |
| Distance from Earth | 51.6 light-years (15.8 parsecs) |
| Constellation | Corona Borealis |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2022 |
Data: NASA Exoplanet Archive, last updated 2022-08-01. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 3929 b
Is GJ 3929 b habitable?
No — GJ 3929 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 3929 b?
GJ 3929 b is about 52 light-years from Earth in the constellation Corona Borealis. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 908,160 years to get there.
How big is GJ 3929 b compared to Earth?
GJ 3929 b has 1.09 times the radius of Earth and about 1.8 times its mass.
How long is a year on GJ 3929 b?
One orbit around GJ 3929 takes 2.6 Earth days — short enough that 140 of its years would fit into one Earth year.
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