Summary of Essential Comet Concepts

Comets

• Comets are significant solar system objects, historically viewed as omens.

Definition

• A comet is defined as a "dirty snowball" or icy mudball with eccentric orbits around the sun.

Categories

• Short Period/Ecliptic Comets:

  • Orbital periods < 200 years.
  • Low inclination, mostly prograde orbits.
  • Often faint with predictable appearances.

• Long Period/Isotropic Comets:

  • Orbital periods in thousands of years.
  • Random inclinations; equal prograde and retrograde orbits.
  • Aphelia can extend to thousands of AU, unpredictable appearances.

Composition

• Composed mainly of ices (H2O, CO2, NH3) with rock and dust.
• Nucleus is small (tens of kilometers) and has a low density.

Structure

• Coma: Forms when surface material vaporizes near the sun, creating a gaseous shell around the nucleus, can reach 500,000 km.
• Tails: Comets have two tails:
  • Ion Tail: Made of ionized gases, straight, points away from the sun, bluish.
  • Dust Tail: Curved, contains various dust particle sizes, yellowish, reflects sunlight.

Origins

• Short Period Comets: Typically originate from the Kuiper Belt with low prograde orbits.
• Long Period Comets: Proposed to come from the Oort Cloud, a theoretical spherical shell around the sun.

Fate

• Comets can lose volatile components over time, risking disintegration or crashing into planets.
• Notable events include Comet Shoemaker-Levy 9's impact on Jupiter.