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Parts-per-million chart of the relative mass distribution of the Solar System, each cubelet denoting 2 × 10 24 kg. This article includes a list of the most massive known objects of the Solar System and partial lists of smaller objects by observed mean radius. These lists can be sorted according to an object's radius and mass and, for the most ...
Ceres (minor-planet designation: 1 Ceres) is a dwarf planet in the middle main asteroid belt between the orbits of Mars and Jupiter. It was the first known asteroid , discovered on 1 January 1801 by Giuseppe Piazzi at Palermo Astronomical Observatory in Sicily , and announced as a new planet .
Ceres' shape is controlled mainly by gravity and spin, with only a 3% departure from hydrostatic equilibrium. Its best-fit shape is a triaxial ellipsoid with dimensions a = 483.1 km, b = 481.0, km and c = 445.9 km, with c being the north-south axis and a and b the semimajor and semiminor equatorial axes.
Ceres is saturated with impact craters.Many have a central pit or bright spot. In the first batch of 17 names approved by the IAU, craters north of 20° north latitude had names beginning with A–G (with Asari being the furthest north), those between 20° north and south latitude beginning with H–R, and those further south beginning with S–Z (with Zadeni being the furthest south).
A rotating object that is massive enough to be in hydrostatic equilibrium will be close in shape to an ellipsoid, with the details depending on the rate of the rotation. At moderate rates, it will assume the form of either a bi-axial or tri-axial ellipsoid. At faster rotations, non-ellipsoidal shapes can be expected, but these are not stable.
Giuseppe Piazzi, discoverer of Ceres, the largest object in the asteroid belt: Ceres was known as a planet, but later reclassified as an asteroid and from 2006 as a dwarf planet. On January 1, 1801, Giuseppe Piazzi , chairman of astronomy at the University of Palermo , Sicily, found a tiny moving object in an orbit with exactly the radius ...
Only one of them – Pluto – has been observed in enough detail to verify that its current shape fits what would be expected from hydrostatic equilibrium. [53] Ceres is close to equilibrium, but some gravitational anomalies remain unexplained. [54] Eris is generally assumed to be a dwarf planet because it is more massive than Pluto.
Generally, a planet's shape may be described by giving polar and equatorial radii of a spheroid or specifying a reference ellipsoid. From such a specification, the planet's flattening, surface area, and volume can be calculated; its normal gravity can be computed knowing its size, shape, rotation rate, and mass. [97]