Gliese 436 b
Planet· orbits Gliese 436
Gliese 436 b - a transiting warm Neptune (~22 Earth masses, ~4 Earth radii) on a tight 2.6-day orbit. Because it transits, its size and density are measured, not guessed; it trails an enormous comet-like tail of hydrogen boiling off into space. Its surface has never been seen.
Open in 3D viewSee Gliese 436 b in the live, interactive 3D map
Key facts
Mass
1.32 × 10²⁶ kg
22.1 M⊕
Radius
26,567 km
4.17× wider than Earth
Surface gravity
12.5 m/s²
1.27× Earth's gravity
Year
2.64 Earth days
Distance from Gliese 436
4,353,298 km
Science
Physical
- Mass
- 1.32 × 10²⁶ kg · 22.1 M⊕
- Radius
- 26,567 km · 4.17× wider than Earth
- Density
- 1,680 kg/m³ · 1.7× water
- Computed from mass and radius
- Surface gravity
- 12.5 m/s² · 1.27× Earth's gravity
- Computed from mass and radius
- Escape velocity
- 25.8 km/s · 2.3× Earth's escape velocity
- Computed from mass and radius
Orbital
- Semi-major axis
- 4,353,298 km
- From the NASA Exoplanet Archive (transit + radial-velocity orbit)
- Eccentricity
- 0.138
- From the NASA Exoplanet Archive (transit + radial-velocity orbit)
- Inclination
- 0.00 °
- From the NASA Exoplanet Archive (transit + radial-velocity orbit)
- Orbital period
- 2.6 days
- From the NASA Exoplanet Archive (transit + radial-velocity orbit)
- Perihelion
- 3,752,543 km
- Computed from the orbital elements
- Aphelion
- 4,954,053 km
- Computed from the orbital elements
- Mean orbital velocity
- 120 km/s
- Computed from the orbital elements
Composition
- Bulk composition
- A warm Neptune of ~22 Earth masses and ~4 Earth radii — because it transits, its size and density are genuinely measured (a volatile-rich world, not rocky). Hubble found it trailing an immense tail of hydrogen boiling off into space. Its cloud tops have never been imaged directly.
- Cloud appearance
- Appearance based on ESO/M. Kornmesser's artist's concept. No spacecraft has imaged this world, so its real appearance is unknown — The banded clouds shown are a representation of its class, shown only in Visual mode; Realism shows a plain spectral colour.
Radiation & temperature
- Insolation
- 30.7 S⊕ · 30.7× the sunlight Earth receives
- Computed from Gliese 436's luminosity and the orbital distance (inverse-square; Earth's sunlight = 1).
- Equilibrium temperature
- 686 K (413 °C)
- Computed model value for its 2.6-day orbit — the transit gives size and density, but not directly a temperature.
Discovery & history
- Method
- Transit detection
- Name
- Designated 'b' under the IAU convention that letters a star's planets 'b', 'c', 'd'... in the order they are discovered (the star itself is the unwritten 'a').
Found by radial velocity in 2004 and caught transiting in 2007 - the first transiting Neptune-sized planet, later shown by Hubble to be shedding a vast hydrogen exosphere.
Images
No official imagery available — this object has never been visited and no officially-licensed depiction exists.