55 Cancri e
Planet· orbits 55 Cancri
55 Cancri e (Janssen) - a transiting lava super-Earth (~8 Earth masses, ~1.9 Earth radii) orbiting its Sun-like star in just 18 hours, its dayside hot enough to melt rock. Because it transits, its size and rocky density are measured; its glowing surface has never been directly seen.
Open in 3D viewSee 55 Cancri e in the live, interactive 3D map
Key facts
Mass
4.77 × 10²⁵ kg
7.99 M⊕
Radius
11,946 km
1.88× wider than Earth
Surface gravity
22.3 m/s²
2.28× Earth's gravity
Year
17.7 hours
0.74 Earth days
Distance from 55 Cancri
2,309,791 km
Science
Physical
- Mass
- 4.77 × 10²⁵ kg · 7.99 M⊕
- Radius
- 11,946 km · 1.88× wider than Earth
- Density
- 6,683 kg/m³ · 6.7× water
- Computed from mass and radius
- Surface gravity
- 22.3 m/s² · 2.28× Earth's gravity
- Computed from mass and radius
- Escape velocity
- 23.1 km/s · 2.06× Earth's escape velocity
- Computed from mass and radius
Orbital
- Semi-major axis
- 2,309,791 km
- From the NASA Exoplanet Archive (transit + radial-velocity orbit)
- Eccentricity
- 0.05
- From the NASA Exoplanet Archive (transit + radial-velocity orbit)
- Inclination
- 0.00 °
- From the NASA Exoplanet Archive (transit + radial-velocity orbit)
- Orbital period
- 17.68 hours
- From the NASA Exoplanet Archive (transit + radial-velocity orbit)
- Perihelion
- 2,194,302 km
- Computed from the orbital elements
- Aphelion
- 2,425,281 km
- Computed from the orbital elements
- Mean orbital velocity
- 228 km/s
- Computed from the orbital elements
Composition
- Bulk composition
- A rocky super-Earth of ~8 Earth masses and ~1.9 Earth radii — because it transits, its size and high (rocky) density are genuinely measured. Its dayside is likely molten. The map shows a Visual-mode lava-world impression, dual-labelled as an artist's concept; the real surface has never been seen, and Realism shows an honest flat spectral colour.
- Surface appearance
- Appearance based on ESO/M. Kornmesser's artist's concept. No spacecraft has imaged this world, so its real appearance is unknown — The surface shown is an artistic representation, shown only in Visual mode; Realism shows a plain spectral colour.
Radiation & temperature
- Insolation
- 2,664 S⊕ · 2,664× the sunlight Earth receives
- Computed from 55 Cancri's luminosity and the orbital distance (inverse-square; Earth's sunlight = 1).
- Equilibrium temperature
- 1,958 K (1,685 °C)
- Computed model value for its 18-hour orbit — hot enough to melt rock; not a directly measured temperature.
Discovery & history
- Method
- Transit detection
- Name
- Designated 'e' 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').
Announced in 2004 and found to transit in 2011, 55 Cnc e became one of the first rocky exoplanets with a measured size around a bright star - a prime target for the study of super-Earth surfaces and atmospheres.
Images
Images from open archives · credit shown per image