ASTR 100Lg

ASTR 100Lg - Alex Steging Astr 100Lg November 12, 2009...

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Astr 100Lg November 12, 2009 Homework #3 1. Walter and Luis Alvarez suggest that the Cretaceous-Tertiary extinction was caused by a “meteorite” impact of an object approximately 10 km across. During this period, 2/3 of all species died out. Evidence for this theory includes mass global death and the presence of iridium rich clay at the cretaceous tertiary boundary in rocks all over the world. Iridium is more common in meteorites than in the Earth’s crust, implying the presence of a meteorite, and the presence of clay, which is a result of flooding. This meteorite impact shot soil and dust into the atmosphere, resulting in a long lasting “Nuclear Winter” which dramatically cooled the Earth, causing mass extinction. 2. The Roche limit of a planet is the specific distance from a planet’s center at which the disruptive tidal force is just as strong as the gravitational force between the particles surrounding the planet. Inside the Roche limit, the tidal forces overwhelm the gravitational pull between neighboring particles, and these particles cannot accrete to form a larger body. Instead, they tend to spread out into a ring around the planet. Nothing would happen to an astronaut within the Roche limit of a planet, as the chemical bonds holding the astronaut together are stronger than disruptive tidal force and gravitational forces. 3. Dwarf planets are a solar system body that is large enough to be spherical in shape and have a circular orbit around the Sun, but not large enough to clear its own path of other bodies. Dwarf planets do not gravitationally dominate their local orbital environment. The term is used for Ceres, Pluto, and Eris. 5. Comet’s often have both a dust tail and an ion tail. Ionized atoms and molecules are swept directly away from the Sun by the solar wind to form a relatively straight ion tail. The distinct blue color of the ion tail is caused by emissions from carbon-bearing molecules such as CN and C 2 . The dust tail is formed when photons of light strike dust particles freed from evaporating nucleus. Light exerts a pressure on any object that absorbs or reflects it. This pressure, called radiation pressure, is weak but strong enough to make fine-grained dust particles in a comet’s coma drift away from the comet. The solar wind has less of an effect on dust than on ions, so the dust tail end up being curved rather than straight. Solar wind causes comet tails to always point away from Sun, regardless of the direction of the comet’s motion. 7. a.) The photosphere of the Sun is the lowest of the three main layers of the Sun which together constitute the solar atmosphere. It is the region in the solar atmosphere from which most of the visible light escapes into space. The photosphere is heated from below by energy streaming outward from the solar interior. This causes the photosphere to appear darker around the edge of the Sun than it does towards the center. The gas at the edge is not as hot and thus not as bright as the deeper, hotter gas seen near the center. It is made primarily of hydrogen and helium and is opaque to visible light because of the
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This note was uploaded on 11/27/2009 for the course ASTR 50800 at USC.

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ASTR 100Lg - Alex Steging Astr 100Lg November 12, 2009...

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