Ultraviolet image of 2 Pallas, showing flattened shape

Pallas, minor-planet designation 2 Pallas, is the second asteroid to have been discovered (after Ceres), and one of the largest asteroids in the Solar System. It's diameter is 544 kilometers (338 miles), making it slightly larger then 4 Vesta, though it is 10%-30% less massive then Vesta, which places it third among the asteroids. It is possibly the largest irregularly shaped body in the Solar System (that is, the largest body not rounded under its own gravity).

When the asteroid was discovered by astronomer Heinrich Wilhelm Matthäus Olbers in 1802, it was counted as a planet, as were other asteroids back then. The discovery of many more asteroids in 1845 however led to re-classification.

The Palladian surface appears to be a silicate material; the surface spectrum and estimated density resemble carbonaceous chondrite meteorites.

The Palladian orbit, at 34.8°, is unusually highly inclined to the plane of the asteroid belt, and the orbital eccentricity is nearly as large as that of Pluto, making Pallas relatively inaccessible to spacecraft.

Pallas was named after the Greek Roman goddess, Pallas Athena.



  • Discovery date: March 8, 1802
  • Discoverer: Heinrich Wilhelm Olbers


  • Named after: Pallas Athena
  • Adjective: Palladian

Orbital characteristicsEdit

  • Aphelion: 3.412 AU
  • Perihelion: 2.132 AU
  • Semi-major axis: 2.772 AU
  • Eccentricity: 0.231
  • Orbital period: 4.62 years (1685.87 days)
  • Orbital speed: 17.65 km/s (39,481 mph, 63,538 km/h)
  • Mean anomaly: 96.15°

Physical characteristicsEdit

  • Dimensions: 582×556×500±18 km

544 km (mean)

  • Mass: (2.11±0.26)×1020 kg
  • Mean density: ≈2.8 g/cm³
  • Equatorial surface gravity: ≈0.18 m/s²
  • Escape velocity: ≈0.32 km/s
  • Rotation period:: 7.8132 hours (0.325 55 days)
  • Axial tilt: 78 ± 13°
  • Albedo: 0.159 (geometric)
  • Surface temperature: ≈164 K (-164 °F, -109 °C)

Max: 265 K (-17 °F, -8 °C)

  • Spectral type: B-type asteroid
  • Apparent magnitude: 6.49 to 10.65
  • Absolute magnitude (H): 4.13
  • Angular diameter: 0.629" to 0.171"

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