Want to stay on top of all the space news? Follow @universetoday on TwitterThe first asteroid discovered was 1 Ceres, or Ceres for short. It was classified as a planet for a long time and is considered a dwarf planet today. It was discovered on January 1, 1801, by Giuseppe Piazza. Ceres has a diameter of 950 km and contains 32% of all of the mass in the main asteroid belt. With such massive dimensions it is easy to see why it was mistaken for a planet in the beginning.
As the first asteroid discovered it has garnered quite a bit of scientific study. It is approximately the size of Texas or 975×909 km with a mass of 9.5×10 20kg. It has enough mass for self gravity which is a major requirement to be considered a dwarf planet. It revolves around the sun every 1679.819 days with a very small axial tilt. The asteroid’s surface can get as warm as -38°C(235 K). The surface of asteroid Ceres is thought to be made up of a mixture of water ice and various watery minerals like carbonates and clay. The asteroid also seems to be differentiated into a rocky core and an icy mantle. It has a brightness magnitude of +6.9 to +9. It can nearly be seen by the unaided eye. When at its brightest, it can be seen with binoculars from nearly anywhere in the world.
Ceres, the first asteroid discovered, follows an orbit of the Sun that takes 4.6 Earth years and is moderately inclined at 10.6° and somewhat eccentric at 0.08. Ceres rotates on its axis every 9 hours and 4 minutes. The asteroid was once thought to be a member of the asteroid family Gefion, but it has been discovered to simply be an interloper with a similar orbit.
The Dawn space mission is scheduled to visit the first asteroid discovered in 2015, shortly after visiting the asteroid Vesta. If this mission is successful it will make space history as the first mission to visit two solar bodies. Scientists are hoping to find evidence that may reclassify Ceres as a ninth planet, replacing Pluto or at least enough evidence to classify Vesta as a dwarf planet.
As the first asteroid discovered, Ceres has been the subject of much discussion and study. Quite a bit is known about the dwarf planet, but there are many things still unknown. The fact that it has massive amounts of water make it a prime target for the study of possible extra-terrestrial life. Maybe the Dawn space mission will relay images that will encourage that study in the future.
Nasa has published a short article about Ceres and Wikipedia has a very in depth article on the topic. Here on Universe Today there are several very good articles about the first asteroid discovered as well as a great episode on Astronomy Cast.