Comets are members of the solar system; that is to say, they travel in orbits around the Sun in a manner fundamentally the same as that of the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn Uranus, Neptune, and Pluto), the asteroids (tiny, rocky, minor planets of which the solar system contains many thousand), and meteors. Many appear regularly. One, Encke’s comet, returns every three years; while others are calculated to return at intervals of thousands of years. Some suddenly appear in the sky or are observed through a telescope as they approach. They travel in a curved path around the Sun and disappear again in the recesses of the solar system, far beyond the range of observation.