Composed of rock and ice, Ceres is the only dwarf planet in the inner Solar System. Gravitational perturbations from Jupiter billions of years ago prevented Ceres from becoming a full-fledged planet.
Ceres was the first object discovered in the asteroid belt when sicilian astronomer Father Giuseppe Piazzi spotted it in 1801. Ceres was initially classified as a planet and later classified as an asteroid. In recognition of its planet-like qualities, Ceres was designated a dwarf planet in 2006 along with Pluto and Eris.
Ceres appears to have a rocky core, an icy mantle and may harbor a remnant internal ocean of liquid water under the layer of ice. Scientists have calculated that this ice mantle may contain as much as 200 million cubic kilometres of water – that’s more fresh water than can be found on planet Earth. The surface is probably a mixture of water ice and various hydrated minerals such as carbonates and clay.
Ceres completes an orbit every 4.6 Earth years and completes a full rotation every 9 hours and 4 minutes.
The surface of the dwarf planet is relatively warm. The maximum temperature measurement was about −38 °C, −36 °F taken on 5 May 1991.
It is believed that Ceres has a weak atmosphere, if any at all. Because Ceres only has about 4% of the gravity of Earth, it must be very hard to keep an atmosphere. Water vapor, however, may have formed a small protective ozone-like layer around at least part of the planet, similar to an “atmosphere.”
NASA’s spacecraft Dawn entered orbit around Ceres on 6 March 2015. Pictures from the spacecraft show a cratered surface.
Mass: 943,000,000,000 billion kg
Diameter: 950 km
Orbit Distance: 413,700,000 km (2.77 AU)
Orbit Period: 4.60 years
Average Surface Temperature: -105°C
Discovery Date: 1st January 1801
Discovered By: Giuseppe Piazzi