Besides the sun, the solar system consists of planets, moons, asteroids, and comets.

Comet Hale-Bopp has a very large nucleus.

One generation passeth away, and another generation cometh: but the earth abideth for ever.

Comets retain a record of conditions from the early solar system.

In July of 1994, Jupiter was hit by pieces of the Shoemaker-Levy comet. Dark areas appeared in Jupiter's atmosphere after the large pieces hit the planet.

Every year, the Earth passes near the path of the comet, and the debris left behind by Swift-Tuttle shows up as meteors in our sky.

Rosetta's probe, Philae, has successfully landed on the comet 67P/Churyumov–Gerasimenko.

Each time the comet passes close to the Sun, it loses some of its material. Over time, it will break up and disappear completely.

Comet Siding Spring is one of the long-period comets, those that require more than 200 years to orbit the Sun. These comets come from the Oort Cloud, a sphere of about a trillion ancient, icy objects located hundreds to thousands of times farther than the planets' orbits.

Rosetta will try to land on a comet in a few hours.