ASTR 1010 1st Edition Lecture 9Outline of Last Lecture I. GravityA. Acceleration of GravityB. Momentum & ForceC. Mass & WeightII. Astronomy FormulasA. DefinitionsB. FormulasOutline of Current LectureI. Solar SystemA. Planets, their Moons & the SunCurrent LectureI. Solar SystemThere are eight major planets with nearly circular orbits. Pluto is smaller than the major planets and has a more elliptical orbit. All large bodies in the solar system orbit in the same direction and nearly the same plane. Most also rotate in the same direction as their orbit.Terrestrial planets are rocky, relatively small, and close to the sun.Jovian planets are gaseous, larger, and further from the sun.A. Planets, their Moons & the SunComparing planets reveals patterns among them. We learn about Earth by studying other planets in the solar system.- The Sun:- Over 99.9% of solar system’s mass- Made mostly of H/He gas (plasma)- Converts 4 million tons of mass into energy each second.- Mercury- Made of metal and rock; large iron core- Desolate, cratered; long, tall, steep, cliffs- Very hot and very cold: 425˚C (day), -170˚C (night)- Venus- Nearly identical to Earth in size; surface hidden by clouds- Hellish conditions due to extreme greenhouse effect- Even hotter than Mercury: 470˚C day and night- Earth- An oasis of life.- The only surface with liquid water in the solar system- Surprisingly large moon.- Mars - Looks almost Earth-like.- Giant volcanoes, a huge canyon, polar caps, and more- Water flowed in the distant past.- Jupiter- Much farther from the Sun and inner planets- Mostly H/He, no solid surface- 300x more massive than the Earth- Many moons (4 Galilean) and rings1. Io (innermost moon): Has active volcanoes all over2. Europa: possible subsurface ocean3. Ganymede: Largest moon in solar system4. Calisto: A large, cratered iceball- Saturn- Giant and gaseous like Jupiter- “Spectacular” rings: not solid, made of small chunks of ice and rock- Many moons, including cloudy Titan. (Approx. 62 total moons)- Uranus- Smaller than Jupiter/Saturn, much larger than Earth- Made of H/He gas & Hydrogen compounds- Extreme axis tilt- Moons and rings- Neptune- Similar to Uranus apart from axis tilt- Many moons (including
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