Comets are icy celestial bodies that orbit the Sun and exhibit a visible atmosphere or coma and sometimes a tail when they come close to the Sun. They originate from the outer regions of the Solar System, primarily the Kuiper Belt and Oort Cloud.
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Comets are composed mainly of water ice, frozen gases, dust, and rocky material.
The nucleus of a comet can range from a few hundred meters to tens of kilometers in diameter.
As comets approach the Sun, solar radiation causes their ices to vaporize and form a glowing coma along with sometimes visible tails pointing away from the Sun.
Cometary tails can be divided into two types: ion (gas) tails and dust tails, both influenced by solar wind and radiation pressure.
Famous comets like Halley's Comet have predictable orbits and can be seen from Earth at regular intervals; Halley's Comet visits every 76 years.
Review Questions
What materials make up the nucleus of a comet?
How do comets develop their characteristic tails?
Where in the Solar System do most comets originate?