The Solar System Wiki

Location in Solar System

In Asteroid belt


Guiseppe Piazzi

Date of Discovery

January 1, 1801

Alternate Name(s)

(1) Ceres



Ceres is the innermost dwarf planet, and the only dwarf planet in the inner Solar System. Ceres is located inside of the Asteroid belt, where it is the largest asteroid. So large, in fact, at 950 kilometers in diameter, that it was classified as a dwarf planet. Ceres is even large enough to maintain hydrostatic equilibrium, or a nearly round shape. Even under extremely dark skies, Ceres is still very difficult to spot due to its apparent magnitude to Earth toward the naked eye, as for any dwarf planet.


Ceres is the innermost dwarf planet in the Solar System. This could mean that Ceres was formed from the remains of a rocky planet that was collided into with a large asteroid. The remains are believed to have created the Asteroid belt. The active asteroids in this belt began to collide, created heat which fused the asteroids and once they gathered enough material, became Ceres.


The surface of Ceres is similar to that of C-type asteroids found in the Asteroid belt. The infrared color spectrum, however, shows high amounts of water under the surface. Carbon minerals are present on Ceres' surface, rising the theory that it might have been formed from carbonaceous meteorites.


Relatively warmer than most dwarf planets due to its distance from the Sun, Ceres has an average surface temperature of 200 degrees Kelvin or about -40 degrees Fahrenheit. The temperature of the surface may be affected by the atmospheric conditions, for water frost reaches the surface, making it colder even when the Sun is overhead the dwarf planet. Some of the water frost can become permanent and make layers of ice visible on the surface. It is believed if this continues, Ceres will have ice caps, similar to that of Earth and Mars.


It is believed Ceres has a weak atmosphere, therefore high amounts of solar radiation cannot be kept out. The solar radiation that breaks through the atmosphere collides with surface water created by melted water frost. The radiation then heats the solid water frost left on the surface and turns it into a gas without turning it into a solid first, which is called sublimation.


Dwarf Planets