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Transcript
Chapter 23 Section 4 Minor Members of Our Solar System Asteroids Comets Meteoroids/Meteors/Meteorites Kuiper Belt Oort Cloud Asteroids • Small rocky bodies; irregular shape • Lie between orbits of Mars & Jupiter (asteroid belt) • Orbital period of 3-6 years – Some asteroids have very eccentric orbits & travel close to the Sun. – Others (larger) regularly pass close to Earth & Moon • Largest asteroid: Ceres— 1,000 km diameter Why track asteroid paths? NASA Capture Pet Asteroid? PHAs (Potentially Hazardous Asteroids) Location of Asteroids Comets • Rocky, metallic material held together by frozen gases (water, ammonia, methane, CO2, and CO) • Elongated orbits (far beyond Pluto) Space Debris Song – Orbital period of most hundreds of thousands of years – Some less than 200 years and encounter inner solar system • Anatomy of a comet: – Coma-glowing head produced as frozen gases vaporized – Nucleus-located in the coma; icy – Tail-typically forms as approach Sun (can extend millions of km); always points AWAY from Sun in curved manner • Radiation pressure—forms dust tail • Solar wind– forms ionized (gas) tail (mainly CO) Halley’s Comet -Periodic comet -Passes Earth every 76 years -Last pass: 1986 -Next pass: 2061 Comet Ison -Originated from Oort Cloud -Most agree it did not survive orbit around Sun Kuiper Belt & Oort Cloud Kuiper Belt • • • Birthplace of short orbital period comets; nearly circular orbits roughly in same plane of planets Located beyond Neptune Most comets we see are Kuiper Belt comets Closer Look at the Kuiper Belt Oort Cloud • Birthplace of long orbital period comets; highly eccentric orbits; not confined to plane of solar system • “3-D shell” around solar system • Very rarely do we observe an Oort Cloud comet Meteoroids • Meteoroid: small solid particle in space; made of iron – Originate from: interplanetary debris, asteroid belt, or remains of a comet • Meteor: meteoroids that enter Earth’s atmosphere; burn once in atmos. – Where does light originate? – Meteor showers Earth encounters swarm of meteoroids traveling same speed/direction link to comets…WHY? • Meteorite: reaches Earth’s surface – Meteor Crater Winslow, Arizona • • • • ~50,000 years ago Originated from asteroid belt ~26,000 mph prior to impact; 150 ft across Crater is roughly – 1 mile wide – 2.4 mile circumference – 550 feet deep