Solar System Debris

Outline

1. How big? * Sand grain to few-hundred miles 2. Where are they? * Main Asteroid Belt * Kuiper Belt * Oort Cloud 3. Asteroids * Rocky/metallic debris left-over from solar system formation * Main asteroid belt * Earth-crossing asteroids 4. Comets * Originate in Kuiper belt & Oort cloud * Ion tail, dust tail, nucleus ('dirty snowball') * Tails point away from sun * Evaporate and/or breakup near Sun 5. Meteoroids * Meteors, meteoroids, meteorites * Meteor shower

Questions

1. Ques. #1, pg. 213.

2. Ques. #2, pg. 213.

3. Ques. #4, pg. 213.

4. Ques. #12, pg. 213.

5. Ques. #13, pg. 213.

6. Ques. #15, pg. 213.

7. What is the cause of meteor showers? Answers

1. Comets, asteroids and meteorites mainly consist of unprocessed material dating from the very early days of the solar system. Thus, they tell us something about the conditions near the time of solar system formation.

2. Asteroid: Small rocky/metallic body orbiting the Sun; diameters range from a few 10s of meter up to several hundred miles; orbits largely confined to the central plane of the solar system. Asteroids are thought to be leftover planetesimals dating from near the time of solar system formation. Comet: Small mainly icy body orbiting the Sun; diameters typically a few miles. Comets are found in the Kuiper belt, which lies near the central plane of the solar system and in the Oort cloud, which extends out to perhaps 100,000 AU from the sun. Orbits of comets in the Oort cloud can lie in any plane. When comets approach the sun, the ice begins to evaporate, forming the characteristic tails. Meteor: The streak of light produced as a small of (typically) rocky material (a meteoroid) plunges through Earth's atmosphere. The light results from frictional heating. Meteoroids originate either as bits of rock chipped from asteroids, or as rocky debris left behind by a comet which approaches the Sun. Meteorite: Piece of a meteoroid that reaches the ground intact. All such chunks of rock originate in asteroids.

3. The asteroid belt is a region between the orbits of Mars and Jupiter where most asteroids are found.

4. Nucleus: hard, icy part of the comet, usually a few miles in diameter. The ice contains embedded rocky/metallic particles. Coma: large region of gas surround nucleus; gas is evaporated ice. Plasma (Ion) Tail: Tail of comet consisting of ions (atoms with one or more electrons mission). Ion tail is blown back from the nucleus by the solar wind. Ion tail has a characteristic blue color. Dust tail: Tail of comet consists of particles of rock/metal released from comet's ice as it evaporates. Tail is blown back from the nucleus by radiation pressure (the pressure exerted by solar photons). Dust tail glows as its particles reflect sunlight. Tails and coma are present only near sun as they result from evaporation of nucleus due to solar heating. Nucleus is present everywhere (that is, until comet evaporates completely, or breaks up).

5. Halley's comet nucleus: core of ice surrounded by crust of very dark material. Crust is punctured by fissures that allow gas & dust from evaporating ice to escape into space. Tails point away from the Sun due to effects of radiation pressure and the solar wind.

6. Kuiper belt: broad region near central plane of solar system, beyond the orbit of Neptune. Oort cloud: large, spherical region centered on the Sun; thought to be about 100,000 AU in radius.

7. A meteor shower occurs when Earth passes through a comet’s debris field (i.e., the solid material released into space as a comet evaporates).