GJ 436 b
GJ 436 b is a Neptune-like planet orbiting GJ 436 in the constellation Leo. It lies about 32 light-years from Earth and was discovered in 2004 using the radial velocity method.
How Big Is GJ 436 b?
GJ 436 b has a radius of 4.17 times that of Earth. Its mass is 22.1 times that of Earth, giving it a density of 1.80 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is GJ 436 b in the Habitable Zone?
The position of GJ 436 b relative to the habitable zone of GJ 436 cannot be precisely determined from the available orbital data.
Orbit and Year Length
A year on GJ 436 b — one full orbit around GJ 436 — lasts 2.64 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.029 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.14).
How Was GJ 436 b Discovered?
GJ 436 b was discovered in 2004 using the radial velocity method, with observations from W. M. Keck 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 436 b?
GJ 436 b is 31.8 light-years (9.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1995. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 559,680 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 436 b scores 0.21, ranking #3,802 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 436
GJ 436
- Mass
- 0.47 M☉
- Radius
- 0.46 R☉
Planetary System
GJ 436 b is the only planet known to orbit GJ 436 so far.
GJ 436 b — Complete Data
| Radius | 4.170 Earth radii (0.372 Jupiter radii) |
|---|---|
| Mass | 22.10 Earth masses (0.070 Jupiter masses) |
| Density | 1.80 g/cm³ (Earth: 5.51) |
| Orbital period | 2.64 days |
| Orbital distance | 0.029 AU |
| Eccentricity | 0.138 |
| Earth Similarity Index | 0.21 |
| Distance from Earth | 31.8 light-years (9.8 parsecs) |
| Constellation | Leo |
| Discovery method | Radial Velocity |
| Discovery facility | W. M. Keck Observatory |
| Discovery year | 2004 |
Data: NASA Exoplanet Archive, last updated 2015-02-05. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 436 b
Is GJ 436 b habitable?
GJ 436 b is not known to orbit within the habitable zone of GJ 436, and as a Neptune-like planet it is an unlikely candidate for life as we know it.
How far away is GJ 436 b?
GJ 436 b is about 32 light-years from Earth in the constellation Leo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 559,680 years to get there.
How big is GJ 436 b compared to Earth?
GJ 436 b has 4.17 times the radius of Earth and about 22.1 times its mass.
How long is a year on GJ 436 b?
One orbit around GJ 436 takes 2.6 Earth days — short enough that 138 of its years would fit into one Earth year.
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