1 Ceres Ceres is the largest object in the solar system's asteroid belt Modern astronomers have classified it as too small to be a planet
7 IT'S A DARK NIGHT IN 1801 AND THE SICILIAN ASTRONOMER GIUSEPPE PIAZZI IS LOOKING FOR COMETS HE NOTICES A TINY STARLIKE OBJECT SINCE IT MOVES SLOWLY ACROSS THE SKY FROM NIGHT TO NIGHT HE THINKS HE HAS FOUND A NEW COMET BUT HE DISCOVERS THAT IT HAS AN ORBIT A PATHWAY AROUND THE SUN MORE LIKE A PLANET THAN A COMET HE NAMES IT CERES AFTER THE PATRON GODDESS OF SICILY BUT HE IS DISAPPOINTED WHEN HE CALCULATES ITS SIZE CERES IS LESS THAN 500 MILES 800 KILOMETERS WIDE BARELY ONE QUARTER THE SIZE OF EARTH'S Moon CERES ISN'T BIG ENOUGH TO DESERVE THE NAME PLANET MERCURY MARS MAIN ASTEROID BELT VENUS EARTH JUPITER Many asteroids can be found in the asteroid belt which orbits the Sun between Mars and Jupiter
This photograph shows Ceres moving in orbit against a starry background 8 MORE LITTLE WORLDS Another tiny world was found the year after Ceres was discovered It is a little smaller than Ceres Astronomers named it Pallas They found two more over the next five years Both are smaller than either Ceres or Pallas Astraea the fifth to be discovered is only 100 miles 160 km wide These little worlds are so small that the astronomers first described them with the term minor planets Most people however know them as asteroids a word that means like stars Modern astronomers have listed several hundred thousand asteroids One estimate has one to two million asteroids orbiting between Mars and Jupiter This region has become known as the asteroid belt At least 98 percent of all known asteroids orbit there As many as four thousand of them are larger than 0 6 mile 1 km across This sounds like an awful lot of material But if every asteroid were to be combined into one big ball it would be less than 900 miles 1 448 km wide This is less than half the size of Earth's Moon Seven Wonders of Asteroids Comets and Meteors FACTS ABOUT Ceres THE LARGEST ASTEROID Ceres is the largest known asteroid It is 568 miles 914 km across almost twice the size of the next largest asteroid It is one fourth the size of all the asteroids in the entire asteroid belt combined It is larger than most of the moons of Saturn and Jupiter Diameter 590 miles 950 km Average distance from the Sun 277 million miles 446 million km Length of year the time it takes to orbit the Sun 1,680 days
Scientists don't know much about what Ceres looks like Even in the largest telescopes it looks like a blurry ball with faint light and dark features It has a large bright spot and a large dark spot These may be giant craters on its surface It may also have a very thin atmosphere and a rocky surface covered in frost This digital illustration shows the orbits of Ceres left Mars center closest to the Sun and Jupiter bottom right as they circle the Sun A NEW KIND of Planet Scientists recently assigned Ceres to an entirely new class of solar system body They are called dwarf planets Ceres was once one of the largest asteroids but under the new classification it has become one of the smallest of the dwarf planets Pluto formerly classified as a planet Ceres and Eris an icy body that orbits far beyond Pluto were the first three objects to be put into this new category
