Scientists believe that comets are made up of material left over from when the Sun and the planets were formed.

If the comet nucleus is pulled into an orbit which carries it close to the Sun, the solar heat will cause the outer layers of the icy nucleus to evaporate.

Most scientists now agree that Chicxulub contains evidence that a huge asteroid or comet crashed into Earth's surface, causing the extinction of more than 70 percent of the living species on the planet, including the dinosaurs.

Since Comet Siding Spring's discovery, astronomers have observed it with many telescopes, including the Hubble Space Telescope.

Comets do not always have tails. They develop a fuzzy, shell-like cloud called a coma, and one, two, or three tails when near the sun.

Comet Siding Spring was discovered in 2013 by astronomers at the Siding Spring Observatory in Australia.

Scientists believe that the particles in Saturn's rings came from the destruction of moons circling the planet. As comets and meteorites smashed the moons, Saturn's gravitational pull shaped the particles into rings.

Halley's Comet will come back in 2061.

The sun is at the center of the solar system, and the planets, asteroids, moons, and comets orbit the sun.

The words " solar system" refer to the Sun and all of the objects that travel around it. These objects include planets, natural satellites such as the Moon, the asteroid belt, comets, and meteoroids.