Comets

Comets are icy bodies orbiting the Sun that become visible from Earth when their elliptical paths bring them near enough to heat up and shed luminous dust and gas. Often called "dirty snowballs," they consist of frozen volatiles—water ice, methane, ammonia—mixed with rock and dust.

When a comet approaches the Sun, solar radiation vaporizes its surface, creating a glowing envelope called a coma and stretching material into a tail that can span millions of kilometers, always pointing away from the Sun due to Solar wind. This transformation has captivated observers across history: ancient astronomers recorded comets as omens, while modern science studies them as pristine remnants of the early solar system.

Most comets originate from the Oort Cloud, a theoretical spherical shell of icy bodies surrounding our planetary system. Others come from the Kuiper Belt, a disk of objects beyond Neptune. Famous periodic visitors like Halley's Comet return in predictable cycles, while others take millennia between visits.

Comets have inspired wonder and dread in equal measure—some were mistaken for celestial threats—yet they're also scientific treasures, containing clues about the solar system's formation and possibly delivering water and organic compounds to early planets.

Related

Halley's Comet, Meteors, Asteroids, Oort Cloud, Solar wind, Observatory