2 Pallas
Asteroid· orbits the Sun
Pallas is the third-largest asteroid, on a steeply inclined, eccentric orbit that sets it apart from most of the belt. It has never been visited.
Open in 3D viewSee 2 Pallas in the live, interactive 3D map
Key facts
Radius
256 km
4% of Earth's radius
Distance from Sun
2.77 AU
Orbital period
4.61 years
Eccentricity
0.2307
Rotation
7.81 hours
Science
Physical
- Dimensions
- 650 × 609 × 512 km · approx. triaxial diameter
- Mass
- 2.04 × 10²⁰ kg · 0.00278 Moon masses
- Density
- 2,906 kg/m³ · 2.9× water
- Computed from mass and radius
- Rotation period
- 7.81 hours
Orbital
- Semi-major axis
- 2.77 AU
- From catalogued orbital elements (MPC)
- Eccentricity
- 0.2307
- From catalogued orbital elements (MPC)
- Inclination
- 34.93 °
- From catalogued orbital elements (MPC)
- Orbital period
- 4.61 years
- From catalogued orbital elements (MPC)
- Perihelion
- 2.13 AU
- Computed from the orbital elements
- Aphelion
- 3.41 AU
- Computed from the orbital elements
- Mean orbital velocity
- 17.9 km/s
- Computed from the orbital elements
Discovery
- Discovered
- March 28, 1802
- Discoverer
- Heinrich Wilhelm Olbers
Composition
- Make-up
- A B-type asteroid of hydrated silicates and carbon-rich material; never visited by a spacecraft.
Radiation & temperature
- Insolation
- 0.13 S⊕ · 13% of the sunlight Earth receives
- Computed from the distance to the Sun (inverse-square; Earth's sunlight = 1), before any atmosphere.
- Geometric albedo
- 0.15
- Geometric (V-band) albedo; Bond albedo not directly measured.
- Equilibrium temperature
- 160 K (-113 °C)
- Computed from albedo + distance from the Sun (airless black body); uses the geometric albedo as an estimate
Discovery & history
- Discovered
- March 28, 1802
- By
- Heinrich Wilhelm Olbers
- Method
- Visual discovery (telescopic)
- Name
- Pallas Athena, the Greek goddess of wisdom and warfare.
Pallas was the second asteroid ever found, discovered by Heinrich Olbers in 1802, a year after Ceres. One of the largest bodies in the asteroid belt, it follows an unusually tilted, eccentric orbit that makes it surprisingly hard to reach. It has never been seen close up — among the largest objects in the inner Solar System never visited by a spacecraft.
Images
Images from open archives · credit shown per image