Earth science

Page
4

 Comets are small bodies made of rocky and metallic pieces held together by frozen gases. Comets generally revolve about the sun in elongated orbits.

Slide 36

23.4 Minor Members of the Solar System

 Coma

• A coma is the fuzzy, gaseous component of a comet’s head.

• A small glowing nucleus with a diameter of only a few kilometers can sometimes be detected within a coma. As comets approach the sun, some, but not all, develop a tail that extends for millions of kilometers.

Slide 37

Comet’s Tail Points Away from the Sun

Slide 38

23.4 Minor Members of the Solar System

 Kuiper Belt

• Like the asteroids in the inner solar system, most Kuiper belt comets move in nearly circular orbits that lie roughly in the same plane as the planets.

 Oort Cloud

• Comets with long orbital periods appear to be distributed in all directions from the sun, forming a spherical shell around the solar system called the Oort cloud.

Slide 39

23.4 Minor Members of the Solar System

 Halley’s Comet

• The most famous short-period comet is Halley’s comet. Its orbital period is 76 years.

Slide 40

23.4 Minor Members of the Solar System

 A meteor is the luminous phenomenon observed when a meteoroid enters Earth’s atmosphere and burns up, popularly called a shooting star.

 A meteoroid is a small, solid particle that travels through space.

 A meteorite is any portion of a meteoroid that reaches Earth’s surface.

Slide 41

23.4 Minor Members of the Solar System

 Most meteoroids originate from any one of the following three sources: (1) interplanetary debris that was not gravitationally swept up by the planets during the formation of the solar system, (2) material from the asteroid belt, or (3) the solid remains of comets that once traveled near Earth’s orbit.

Slide 42

Major Meteor Showers