Ceres; minor-planet designation: 1 Ceres) is the largest object in the main asteroid belt between the orbits of Mars and Jupiter. It comprises a quarter of the mass of the belt and, at 940 km (580 mi) in diameter, is the only asteroid large enough to be rounded by its own gravity, although Vesta and perhaps other asteroids were so in the past. This makes Ceres both the smallest recognized dwarf planet and the only one inside Neptune's orbit.
The first asteroid known, Ceres was discovered on 1 January 1801 by Giuseppe Piazzi at Palermo Astronomical Observatory. It was originally considered a planet, but was reclassified as an asteroid in the 1850s after many other objects in similar orbits were discovered. It has since been classified both as a C-type asteroid and, due to the presence of clay minerals, as a G-type asteroid.
Size and Distance :
With a radius of 296 miles (476 kilometers), Ceres is 1/13 the radius of Earth. If Earth were the size of a nickel, Ceres would be about as big as a poppy seed.
From an average distance of 257 million miles (413 million kilometers), Ceres is 2.8 astronomical units away from the sun. One astronomical unit (abbreviated as AU), is the distance from the sun to Earth. From this distance, it takes sunlight 22 minutes to travel from the sun to Ceres.
Orbit and Rotation :
Ceres takes 1,682 Earth days, or 4.6 Earth years, to make one trip around the sun. As Ceres orbits the sun, it completes one rotation every 9 hours, making its day length one of the shortest in the solar system.
Ceres' axis of rotation is tilted just 4 degrees with respect to the plane of its orbit around the sun. That means it spins nearly perfectly upright and doesn't experience seasons like other more tilted planets do.
Physical Characteristics :
Ceres is more similar to the terrestrial planets (Mercury, Venus, Earth and Mars) than its asteroid neighbors, but it is much less dense. One of the similarities is a layered interior, but Ceres' layers aren’t as clearly defined. Ceres probably has a solid core and a mantle made of water ice. In fact, Ceres could be composed of as much as 25 percent water. If that is correct, Ceres has more water than Earth does. Ceres' crust is rocky and dusty with large salt deposits. The salts on Ceres aren’t like table salt (sodium chloride), but instead are made of different minerals like magnesium sulfate.
Ceres has a very thin atmosphere, and there is evidence it contains water vapor. The vapor may be produced by ice volcanoes or by ice near the surface sublimating (transforming from solid to gas).
Ceres was the first object considered to be an asteroid.
Italian astronomer Giuseppe Piazzi discovered and named Ceres in early 1801.
The first visit to Ceres is due in 2015.
NASA’s Dawn spacecraft has been making its way to Ceres from the asteroid Vesta since September 2012. There is high interest in this mission since Ceres will be the first Dwarf Planet visited by a spacecraft and is one possible destination for human colonisation given its abundance of ice, water, and minerals.
Ceres has a mysterious white spot.
This can be seen in both the old Hubble images and the more recent photos taken by the Dawn spacecraft on its approach.
Every second Ceres loses 6kg of its mass in steam.
Plumes of water vapour shooting up from Ceres’ surface were observed by the Herschel Space Telescope this was the first definitive observation of water vapour in the asteroid belt. It’s thought this is caused when portions of Ceres’ icy surface warm.
Ceres accounts for one third of the mass in the asteroid belt.
Despite this it is still the smallest and least massive of the dwarf planets.
For roughly the first 50 years after its discovery Ceres was frequently referred to as a planet.
By the end of 1851 14 other similar objects had been discovered and it did not take long before these instead became known as “minor planets”. Ceres was eventually reclassified as a Dwarf Planet alongside Pluto in 2006.
Ceres is the only dwarf planet with no moons.
The other dwarf planets; Pluto, Haumea, Makemake and Eris all have at least one moon.