4 Vesta

Asteroid· orbits the Sun

Vesta is the second-most-massive asteroid and a differentiated protoplanet — with a basaltic crust, olivine mantle and iron core — studied up close by NASA's Dawn mission in 2011–2012. It is the source of the HED meteorites.

Open in 3D viewSee 4 Vesta in the live, interactive 3D map

Key facts

Radius

263 km

4% of Earth's radius

Distance from Sun

2.36 AU

Orbital period

3.63 years

Eccentricity

0.0902

Rotation

5.34 hours

Science

Physical

Mean radius: 263 km · 4% of Earth's radius
Mass: 2.59 × 10²⁰ kg · 0.00353 Moon masses
Density: 3,411 kg/m³ · 3.4× water; Computed from mass and radius
Rotation period: 5.34 hours

Orbital

Semi-major axis: 2.36 AU; From catalogued orbital elements (MPC)
Eccentricity: 0.0902; From catalogued orbital elements (MPC)
Inclination: 7.14 °; From catalogued orbital elements (MPC)
Orbital period: 3.63 years; From catalogued orbital elements (MPC)
Perihelion: 2.15 AU; Computed from the orbital elements
Aphelion: 2.57 AU; Computed from the orbital elements
Mean orbital velocity: 19.4 km/s; Computed from the orbital elements

Discovery

Discovered: March 29, 1807
Discoverer: Heinrich Wilhelm Olbers

Composition

Make-up: A differentiated body: a basaltic crust over an olivine-rich mantle and an iron–nickel core; the source of the HED meteorites found on Earth.

Radiation & temperature

Insolation: 0.179 S⊕ · 18% of the sunlight Earth receives; Computed from the distance to the Sun (inverse-square; Earth's sunlight = 1), before any atmosphere.
Bond albedo: 0.18 · reflects 18% of incoming sunlight
Equilibrium temperature: 172 K (-101 °C); Computed from albedo + distance from the Sun (airless black body)

Discovery & history

Discovered: March 29, 1807
By: Heinrich Wilhelm Olbers
Method: Visual discovery (telescopic)
Name: The Roman goddess of the hearth — the name was chosen by mathematician Carl Friedrich Gauss.

Vesta, the fourth asteroid found, is the brightest and the only one ever visible to the naked eye. Heinrich Olbers discovered it in 1807. Far from being a simple rock, Vesta turned out to be a differentiated 'protoplanet' with a basaltic crust, a mantle and an iron core — a survivor from the era of planet formation. The Dawn spacecraft orbited it in 2011–12, and meteorites blasted off Vesta long ago still fall to Earth today.