Chapter 25

Chapter 25 - Note that the following lectures include...

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Note that the following lectures include animations and PowerPoint effects such as fly ins and transitions that require you to be in PowerPoint's Slide Show mode (presentation mode).
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Meteorites, Asteroids, and Comets Chapter 25
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In Chapter 19, we began our study of planetary astronomy by asking how our solar system formed. In the five chapters that followed, we surveyed the planets, but we gained only limited insight into the origin of the solar system. The planets are big, and they have evolved as heat has flowed out of their interiors. In this chapter, we have our best look at unevolved matter left over from the solar nebula. These small bodies are, in fact, the last remains of the nebula that gave birth to the planets. This chapter is unique in that it covers small bodies. In past chapters, we have used the principles of comparative planetology to study large objects— the planets. In this chapter, we see that the same principles apply to smaller bodies, but we also see that we need some new tools in order to think about the tiniest worlds in the solar system. Guidepost
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I. Meteorites A. Meteoroid Orbits B. Meteorite Impacts on Earth C. An Analysis of Meteorites D. The Origins of Meteorites II. Asteroids A. The Asteroid Belt B. Nonbelt Asteroids C. Composition and Origin III. Comets A. Properties of Comets B. The Geology of Comet Nuclei C. The Origin of Comets Outline
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IV. Impacts on Earth A. Impacts and Dinosaurs B. The Tunguska Event Outline (continued)
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Appearances of comet Kohoutek (1973), Halley (1986), and Hale-Bopp (1997) caused great concern among superstitious. Comet Hyakutake in 1996 Throughout history, comets have been considered as portents of doom, even very recently: Comets of History
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Meteorites Distinguish between: Meteoroid = small body in space Meteor = meteoroid colliding with Earth and producing a visible light trace in the sky Meteorite = meteor that survives the plunge through the atmosphere to strike the ground. .. . Sizes from microscopic dust to a few centimeters. About 2 meteorites large enough to produce visible impacts strike the Earth every day. Statistically, one meteorite is expected to strike a building somewhere on Earth every 16 months. Typically impact onto the atmosphere with 10 – 30 km/s (≈ 30 times faster than a rifle bullet).
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Meteor Showers Most meteors appear in showers, peaking periodically at specific dates of the year.
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Radiants of Meteor Showers Tracing the tracks of meteors in a shower backwards, they appear to come from a common origin, the radiant. Common direction of motion through space.
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Meteoroid Orbits Meteoroids contributing to a meteor shower are debris particles, orbiting in the path of a comet. Spread out all along the orbit of the comet. Comet may still exist or have been destroyed.
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Chapter 25 - Note that the following lectures include...

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