Ceres was discovered on the first day of the 19th century, Jan. 1, 1801, by Giuseppe Piazzi. The resolution of Piazzi's telescope was so low that he could only make out Ceres as a point of light, so he called the new class of solar system object an "asteroid," which means "starlike." This is ironic because asteroids are unlike stars in almost every way imaginable.Continue Reading
In addition to being the first asteroid to be discovered, Ceres is also the largest. It is roughly spherical and approximately 980 kilometers across. Set next to Earth, it would reach from El Paso to the Texas-Louisiana border. Ceres has a surface area of 2.85 million square kilometers, which means that if it could be spread out in two dimensions, it would cover an area somewhat larger than Argentina.
Ceres and the other asteroids of the Main Belt are remnants of the solar system's earliest period. Gravitational tugs from Jupiter and Mars prevented these asteroids from accreting into a full-sized planet. Unlike the other asteroids, Ceres might have a mantle made largely of water ice. This ice is periodically warmed by sunlight and erupts onto the dwarf planet's surface. If Ceres is 25 percent composed of ice, it contains more water than all of the oceans on Earth.Learn more about Comets & Asteroids