Comets of the Solar System

Comets

• Comets are composed of ice, small particles of dust, and a mixture of frozen gases, carbonaceous particles, and refractory grains.
• They are primitive bodies of the Solar System.
• When heated by solar radiation, comets lose matter.

Cometary Behavior

• Comets spend most of their time at great distances from the Sun, appearing as a fuzzy patch of light.
• As they approach the Sun, their coma grows in size and brightness.
• A tail develops and reaches its maximum size at perihelion.
• As the comet recedes from the Sun, the reverse process occurs.

Cometary Structure

• Nucleus: small, typically a few kilometers in diameter.
• Coma: 10^4 to 10^5 kilometers in diameter.
• Head: consists of the nucleus and coma.
• Tail: 10^7 to 10^8 kilometers in length.

Types of Comet Tails

• Type I: Plasma/ion tail, resulting from the interaction of ions in the coma with the solar wind.
• Type II: Dust tail, composed of dust embedded in the nucleus.

Comet Tail Characteristics

• Ion tails are approximately straight and often made of glowing, linear streamers.
• Ion tails are more strongly influenced by the solar wind than the Sun's gravity, so they always point directly away from the Sun.
• Dust tails are slightly curved due to the heavier dust particles following the comet's orbit.

Classification of Comets

• Comets can be classified as New or Old.
• Comets can be classified based on their orbital periods:
  • Short period (p < 200 years): e.g. Halley, Tempel 1, Tempel 2, Encke, etc.
  • Long period (p > 200 years): e.g. Hale Bopp, Hayakutake, Levy Rudenko, etc.
• There are currently less than 1000 cataloged comets.
• The ratio of Long Period to Short Period Comets is approximately 5:1.