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What is a comet?

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Quick answer

A comet is an icy body from the outer solar system that grows a glowing tail when it nears the Sun. As the Sun's heat vaporizes its ice, gas and dust stream off, forming a bright tail that always points away from the Sun.

Key things to understand

  1. It's a 'dirty snowball' of ice, dust, and rock.
  2. Most originate in the cold, distant edges of the solar system.
  3. Nearing the Sun, its ice sublimates into gas and dust.
  4. That released material forms a glowing tail, swept back by the solar wind.
  5. The tail always points away from the Sun, not behind the comet's path.

People also ask

Why does a comet have a tail?
The Sun's heat vaporizes the comet's ice, releasing gas and dust that the solar wind sweeps into a glowing tail pointing away from the Sun.
What is a comet made of?
A mix of frozen ices (water, carbon dioxide), dust, and rock — often described as a 'dirty snowball.'
Where do comets come from?
From the frozen outer regions of the solar system — the Kuiper Belt and the distant Oort Cloud.