1. 1 Ch. 23: “Touring Our Solar System” 23.4: “Minor Members of the Solar System”

2. 2 The Asteroids What are the asteroids? a) The broken up remnants of a destroyed planet? b) Material that never managed to form into a planet? The current balance of opinion favors the latter, due to the existence of stable orbits between Mars and Jupiter. An asteroid is a small, rocky body whose diameter can range from a few hundred kilometers to less than a kilometer. Most lie between Mars and Jupiter and have orbital periods of 3-6 years.

3. 3 Irregular Orbits of Asteroids

4. 4 Comets Small body composed of chunks of rock and metal held together by ice (water, ammonia, methane, carbon dioxide) Anatomy of a comet –Coma: glowing “head” of the comet; as comet approaches the sun, solar winds vaporize the frozen gases causing the nucleus to glow –Tail: the solar wind that vaporizes the frozen gases also blows the gas away forming a long tail (millions of kilometers)

5. 5 Comet’s Tail Points Away from the Sun

6. 6 Some Comets

7. 7 Comets Comets originate in one of two locations –Kuiper Belt: orbital area outside of Neptune and lies in the same plane as the solar system Comets that originate here have very short orbital periods (ie Halley’s comet; 76 years) –Oort Cloud: 360 degree sphere around the solar system Comets that originate here have long orbital periods

8. 8 Kuiper belt and Oort cloud

9. 9 Meteoroids 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.

10. 10 Meteoroids 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.

11. 11 Major Meteor Showers