ASTR 1010 1st EditionLecture 22Outline of Last Lecture I. SaturnA. AtmosphereB. PropertiesC. Magnetic PropertiesD. Internal StructureE. SatellitesII. UranusIII. NeptuneIV. PlutoOutline of Current LectureI. CometsII. AsteroidsIII. MeteorsCurrent LectureI. Comets1. Nucleus- Diameter: 1 – 10 km- Mass: 0.1 – 0.01% Mass of Moon- Composition: Probably aggregates of ice and stones2. Coma (Head)- First visible at approx. 5 AU- Composition: Gas and dust- Size: Approx. the diameter of Earth – Sun3. Tail- First Approx. 2 AU- Grows in length as it approaches the sun (L = 1 AU)- Always points away from the sun due to solar wind components- Ion tail: straight- Dust tail: curved4. Orbits – Random- 50% Retrograde- 50% Direct- All inclinations- Short period comets – Assoc. with Jupiter or SaturnHalley’s Comet – 76 year period5. Origin - Kuiper Belt- Oort CloudII. Asteroids1. Size- Ceres: 780 km- Pallas: 490 km- Juno: 200 km- Vesta: 390 km2. Orbits- Most lie between Mars and Jupiter, Kirkwood Division- Trojan Asteroids- Apollo Asteroids: Distance = 1 AU, Icarus = 1.08 AU, Eros = 1.4 AU (14,000,000 MI)- Amor Asteroids: Cross Mars’ orbitIII. Meteors 1. Types - Sporadic: asteroid origin- Showers: cometary debrisGeminidsPerseids2. Nomenclaturea. Meteor: visible phenomenon in the atmosphereb. Meteoroid: physical object in spacec. Meteorite: object that is recoverable on Earthd. Bolide: meteor that produces a noisee. Fireball: unusually bright meteor3. Composition- Iron: 8% of total (75% that are recovered)- Stone: 35% of total (Less than 10% recovered)- Stony/Iron: same as stones- Tektites: black glossy
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