AS101 Lecture 24

AS101 Lecture 24 - AS101 Lecture 24 Logistics: Night Lab:...

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AS101 Lecture 24 Logistics: • Night Lab: Last Lecture: • Rings • Solar system debris Today’s Lecture: • Finish comets • Cosmic Collissions
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Comet Videos
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Anatomy of a comet Albedo of Halley’s nucleus is 3% - darker than charcoal Its density is considerably less than 1 g/cm 3 Gabrielle Morella: What is the nucleus made of?
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Nucleus of Comet A “dirty snowball” Source of material for comet’s tail
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Catching stardust It is 99.8% Air Provides 39 times more insulation than the best fiberglass insulation Is 1,000 times less dense than glass Comet Wild 2, Zoom, Motion, Orbit, Fly-by
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Comets eject small particles that follow the comet around in its orbit and cause meteor showers when Earth crosses the comet’s orbit.
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Meteors in a shower appear to emanate from the same area of sky because of Earth’s motion through space
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Meteor shower due to dead comets
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Cometary Meteor: Shoemaker-Levy 9 comet discovered in 1992: • previous encounter with Jupiter broke it into a string of fragments • the comet was on a collision course with Jupiter Something similar had happened to Callisto. This crater chain is evidence that a string of nuclei once impacted it.
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Impacts
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Explosions on Surface
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Did an impact kill the dinosaurs?
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Mass Extinctions Fossil record shows occasional large dips in the diversity of species: mass extinctions . Most recent was 65 million years ago, ending the reign of the dinosaurs.
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Dinosaur fossils in lower rock layers No dinosaur fossils in upper rock layers Thin layer containing the rare element iridium
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This note was uploaded on 04/14/2011 for the course ASTRO 101 taught by Professor Oppenheim during the Spring '11 term at BU.

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AS101 Lecture 24 - AS101 Lecture 24 Logistics: Night Lab:...

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