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Asteroids and Comets


In addition to the planets and their moons, the solar system teems with small bodies following their own independent elliptical paths around the Sun. Variously called asteroids, minor planets, comets, or just small bodies, these tumbling rocks and iceballs are remnants of the formation of the solar system.

We can distinguish between a comet and an asteroid solely on the basis of the object's appearance through a telescope. If a newly discovered object appears fuzzy, then it is a comet. A large population of asteroids travels around the Sun between the orbits of Mars and Jupiter. A large population of cometary nuclei can be found outside the orbit of Neptune. But there are significant groups of bodies that travel the space between and among the planets. And some objects currently identified as "asteroids" may actually be extinct cometary nuclei. Finding, classifying, and tracking all of these small objects is a complex task.

Studying asteroids and comets can tell us a great deal about the history of our solar system and even our planet. But there's another reason for studying them: some of these bodies, known as near-Earth objects or NEOs, are on trajectories that could have an effect on the future of our planet. It doesn't matter if an NEO is a comet or an asteroid -- if it's big, and it hits the Earth, it will be bad news. For that reason, locating, tracking, and understanding the nature of the solar system's supply of comets and asteroids is a very high priority.