The planet Mars and the star Spica team up for a beautiful showing in the southwest this evening. As night falls, bright orange Mars is just a degree or two above Spica — less than the width of a finger held at arm’s length. If you draw a line from Spica to Mars and continue it upward by less than the width of your fist, you’ll come to two members of our own solar system that are staging an even closer encounter — Ceres and Vesta. They’re not quite bright enough to see with the eye alone, though — you need a telescope to spot them. Ceres is the largest object in the asteroid belt — a wide band of rubble between the orbits of Mars and Jupiter. It’s a ball of rock and ice about one-quarter the diameter of the Moon. Despite its diminutive size, a few years ago Ceres was classified as a dwarf planet — one of five objects to receive that designation so far. Vesta is the second most-massive asteroid after Ceres. It’s about half the size of Ceres, but it’s also closer to Earth, and its surfac
