Asteroids and Comets

Asteroids and Comets. . , You are standing in the "asteroid belt," a region between the orbits of Mars and Jupiter where countless rocks called asteroids orbit the Sun. Every so often icy body called comets pass through this region on their way to the inner solar system. , , You are walking through a scale model of the solar system. The real solar system is 10 billion times larger. At this scale even the largest asteroids are too small to be seen. Look at the map below to see where you are. , , Voyage to an Asteroid , Welcome to Ida, a medium-sized asteroid about 40 miles (60 km) across. The little object is Dactyl, Ida's moon. Gravity is so weak on Ida that you could easily jump as high as the Washington Monument. , , Home of the Asteroids , A million asteroids larger than half a mile (0.8 km) across can be found here in the asteroid belt, but they are so spread out that this space is mostly empty. , , Long known as the largest asteroid, Ceres is 580 miles (940 km) across. In 2006, it was renamed a "dwarf planet." , , Voyage to Halley's Comet , Every 76 years, Halley's Comet journeys from beyond Neptune into the inner solar system. Once inside the orbit of Jupiter, solar heat begins vaporizing ice on the surface of this large dirty snowball the size of a city. The solar wind and sunlight sweep ejected gas and dust into 2 majestic tails, which can grow nearly long enough to span the distance between Earth and the Sun. Halley's Comet returns in 2061. , , The Outer Boundaries of the Solar System , The solar system may contain a trillion comets, but very few venture inside the orbit of Neptune. On the scale of this model solar system, comets could be found up to 900 miles (1,500 km) from where you are standing. , Walk to Jupiter about 55 steps. , , Imagine , When passing the Sun, some comets travel fast enough to go from New York to California in 18 seconds. , , Walk to Mars about 28 steps