Lecture7

Lecture7 - The Solar System and its Origin The scale of...

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1 The Solar System and its Origin Our Goals for Learning • What does the solar system look like? The solar system is mostly empty space The Sun is huge Over 1 million Earths can fit inside the Sun There are 8 planets with unique properties but many common features The scale of solar system The size of the planets drawn to scale; the Sun is huge! The Sun • contains over 99.9% of solar system’s mass • converts 4 million tons of mass into energy each second Our star 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)
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2 Venus • nearly identical in size to Earth; surface hidden by thick clouds • hellish conditions due to an extreme greenhouse effect: • even hotter than Mercury: 470°C, both day and night • atmospheric pressure equivalent to1 km deep in Earth’s oceans • no oxygen, no water, … • how did it end up so different from Earth? Earth • an oasis of life; bio-generated oxygen in atmosphere • the only surface liquid water in the solar system; about 3/4 of surface covered by water • a surprisingly large moon Earth and Moon to scale Mars • Looks almost Earth-like, but don’t go without a spacesuit! • Giant volcanoes, a huge canyon, polar caps, more… • Water flowed in the distant past; could there have been life? Jupiter • Much farther from Sun than inner 4 planets (more than twice Mars distance) • Also very different in composition: mostly H/He; no solid surface • Gigantic for a planet: 300 Earth mass; >1,000 Earth volume • Many moons, rings…
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3 Moons can be as interesting as the planets themselves, especially Jupiter’s 4 large “Galilean moons” (first seen by Galileo) Io (shown here): yellowish, active volcanoes all over Europa : possible subsurface ocean Ganymede : largest moon in solar system — larger than Mercury Callisto : a large, cratered “ice ball” with unexplained surface features Saturn • giant and gaseous like Jupiter • most spectacular rings of the 4 jovian planets • many moons, including cloud-covered Titan • currently under study by the Cassini spacecraft Uranus • much smaller than Jupiter/Saturn, but still much larger than Earth • made of H/He gas, hydrogen compounds (H 2 O, NH 3 , CH 4 ) extreme axis tilt nearly tipped on its “side” — makes extreme seasons during its 84-year orbit. • moons also tipped in
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Lecture7 - The Solar System and its Origin The scale of...

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