Ceres is the smallest identified dwarf planet in the Solar System and the only one in the asteroid belt. It was discovered on 1 January 1801, by Giuseppe Piazzi, and for half a century it was classified as the eighth planet. It is named after Ceres, the Roman goddess of growing plants, the harvest, and motherly love. With a diameter of about 950 km (590 miles), Ceres is by far the largest and most massive body in the asteroid belt, and contains a third (32%) of the belt's total mass. Recent observations have revealed that it is spherical, unlike the irregular shapes of smaller bodies with lower gravity. The surface of Ceres is probably made of a mixture of water ice and various hydratedminerals like carbonates and clays. Ceres appears to be differentiated into a rockycore and ice mantle. It may harbour an ocean of liquid water underneath its surface. From the Earth, Ceres' apparent magnitude ranges from 6.7 to 9.3, and hence at its brightest it is still too dim to be seen with the naked eye. The unmanned Dawnspacecraft, launched on 27 September 2007 by NASA, is expected to be the first to explore Ceres after its scheduled arrival there in 2015.
The Pioneer plaque, which was included on both Pioneer 10 and Pioneer 11 unmanned spacecraft, the first man-made objects to leave our solar system. Made from gold-anodisedaluminium, the plaque shows the figures of a man and a woman along with several symbols that are designed to provide information about the origin of the spacecraft. However, the mean time for the spacecraft to come within 30 astronomical units of a star is longer than the current age of our galaxy.
