AST 115 1st Edition Lecture 16 Outline of Last Lecture I. Extra-Solar Planets (Exoplanets)a. DifficultiesII. Detection Techniquesa. Radial Velocity Methodb. Astrometric Methodc. Stellar Transit Methodd. Gravitational “Microlensing”e. Direct ImagingIII. ResultsIV. Notable discoveriesV. Latest NewsOutline of Current Lecture I. Eartha. Physical propertiesb. Atmospherec. Surface pressured. Surface temperaturee. Atmospheric layersf. Surfaceg. Interiorh. Magnetic fieldII. Earth’s Moona. Physical propertiesb. Atmospherec. Surface temperatured. Surface featurese. OriginCurrent Lecture Terrestrial Planets and their Moonso Physical Properties of Earth- Diameter is about 8,000 miles- Mass is about 6 sextillion metric tons (6 ×1024 kg)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Average density is 5.5 gm/cm3o Earth’s atmosphere- Composition Primordial : mostly CO2 H2O N2 and others Current: 78% N2 21% O2 Traces of CO2 and others- Surface pressure 14.7 lb/¿2 (1 “bar”)- Surface temperature Max → 134˚F (Death Valley 1915) 330˚K Min → -136˚F (Antarctica 2010) 190˚K Earth’s global average annual (as of 2013) surface temperature was about 58˚F (287˚K).- Atmospheric layers Troposphere Stratosphere Mesosphere Thermosphere The Ozone Layer is the layer near the top of the Stratosphere Depletion of O3 Chlorofluorocarbons = CFCs Consequences: increased solar UV damage to plants and animals (NOT global warming)o Surface of the Earth- Plate tectonics: process of Earth’s crustal development due to relative motion of about 16 plates that the crust is made up of.- Leads to earthquakes, volcanoes, mid-ocean rifts, and recycling of the crust.o Interior of the Earth- Chemical differentiation: process in a fluid object where higher density material sinks to form a central core. Lower density material rises to form a crust with an intermediate mantle.- There are 4 layers of Earth’s interior Crust Inner core Outer core Mantle- Estimated conditions of the center of the Earth: Temperature is about 5,000˚K Pressure is about 20,000 tons/¿2 Central density is about 17 gm/cm3 o Earth’s magnetic field- Magnetosphere: the region occupied by the magnetic field of the planet. It is produced by charged, fluid material in the interior of a (rapidly) rotating planet.o Earth’s Moon- Physical properties: Diameter is about 2,000 miles (about ¼ Earth’s diameter) Mass is about 1/81 Earth’s mass Average density is 3.3 gm/cm3 (3,300 kg/m3) Surface gravity is about 1/6 Earth’s surface gravity (1/6 g).- Atmosphere: None- Surface Temperature Max → 265˚F (about 400˚K) Min → -300˚F (about 100˚K)- Lunar surface features 1) Craters – most formed by a high speed impact of solid debris (asteroids and meteoroids). 2) Maria (plural), Mare (singular) – “seas” (they are actually solidified lava plains). 3) Mountains/mountain ranges – not formed by the same process as mountain ranges formed on Earth (actually are rims of huge ancient craters). 4) Rays – white/light colored streaks emanating from impact craters (due to secondary crater formation from ejecta). 5) Rilles – from Earth, these resemble fine cracks. They are actually long canyons formed by lava flows from collapsed lava tubes.- Origin of the Moon (possibly explanations): Fission: the Moon split off from Earth Capture: the Moon formed elsewhere and was captured by Earth’sgravity Co-creation (sister): the Moon and the Earth accreted at the same time. The Moon developed from particles that were in orbit around the forming Earth. Collision-Ejection theory: the Moon may have formed when the young, differentiated Earth was struck with a glancing blow by a young differentiated proto-planet the size of Mars. The material coalesced to make the
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