Asteroids, Comets, and Meteors

There are a huge number of objects within our solar system besides planets. Composed mostly of rock, ice, and dust, they can be larger than Pluto or as small as a grain of sand.

Asteroids are small, rocky bodies, most of which are located in the asteroid belt between Mars and Jupiter. They are very faint, and you’ll need a good ephemeris to find them with a small telescope. Of the thousands of known asteroids, Vesta is the easiest to observe and can sometimes been seen with the naked eye.

Comets are generally much farther away from the Sun than asteroids, but their elongated orbits bring them close to the Sun for short periods of time. Comets with shorter orbits—such as Halley’s comet, which returns every 76 years—pass the Sun more often than others. When comets come near the Sun, they grow two tails: a dust tail and an ion tail (which is less visible). Comets with clear tails are rarely visible to the naked eye. On any given night, more than a dozen comets can be seen through a telescope.

So-called “shooting stars” aren’t stars at all—they’re meteors, pieces of rock floating in space (most of which are smaller than a grain of sand) that burn up when they hit the Earth’s atmosphere, making bright streaks across the sky. Meteors hit the Earth all the time but are visible only at night.

Occasionally, swarms of meteors hit the Earth, resulting in a close succession of shooting stars. These events are known as meteor showers, the most impressive of which are the Leonids (because they appear near the constellation Leo), which occur every year in November. During that time, you can spot up to 70 shooting stars in one hour.