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Lecture

7.1 Studying the Solar System


Department
Astronomy & Astrophysics
Course Code
AST101H1
Professor
C.B.Netterfield

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CHAPTER 7: OUR PLANETARY SYSTEM
7.1 Studying the Solar System
Comparative Planetology
-comparing the worlds to one another, seeking to understand their similarities and difference
-sun and planets are all quite small compared to the distances between them
The Sun
-contains more than 99.9% of the total mass in our solar system Æ more than a thousand times more
massive as everything else in the solar system combined
-composition: 98% hydrogen and helium, 2% others
-the largest and brightest object in our solar system
-QRWVROLGLW·VKRWK\GURJHQDQGKHOLXPJDV
-VRXUFHRIWKHVXQ·VHQHUJ\OLHVGHHSLQLWVFRUHZKHUHWHPSHUDWXUHVDQGSUHVVXUHVDUHVRKLJKWKDWWKH
sun is a nuclear fusion power plant
-each second, fusion transforms about 600 million tons of WKHVXQ·VK\GURJHQLQWRPLOOLRQWRQVRI
helium
-the missing 4 million tons becomes energy
-shone steadily for almost 5 billion years and will continue to shine for some 5 billion years more
-most influential object in our solar system
-its gravity governs the orbits of the planets
-its heat is the primary influence on the temperatures of planetary surfaces and atmospheres
-it is the source of virtually all the visible light in our solar system
-charged particles flowing outward from the sun (solar wind) help shape planetary magnetic fields
and can influence planetary atmospheres
Mercury
-composition: rocks, metals
-mostly iron
-most metal-rich planet
-no moons
-the innermost planet of our solar system
-smallest of the first 8 planets
-desolate, cratered world with no active volcanoes, no wind, no rain and no life
-no air to scatter sunlight or colour
-hot and cold extremes
-unusual rotation pattern ² caused by the tidal forces from the Sun
-58.6 day rotation period
-87.9 day orbital period
-rotates exactly three times for every 2 orbits around the Sun
-days and nights last about 3 months each
-daytime Æ ·&
-nighttime Æ -·&
Venus
-composition: rocks, metals
-no moons
-2nd planet from the Sun
-nearly the identical size to Earth
-rotates very slowly and in the opposite direction of Earth
-days and nights are very long
-sun rises west and sets east
-H[WUHPHJUHHQKRXVHHIIHFWEDNHV9HQXV·VXUIDFHWR·&
-traps heat so effectively
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