Astr Sol SysCoReq ASTR 1211S
Astr Sol SysCoReq ASTR 1211S ASTR 1010
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This 39 page Class Notes was uploaded by Dr. Deion Conroy on Monday October 12, 2015. The Class Notes belongs to ASTR 1010 at Georgia Southern University taught by James Higdon in Fall. Since its upload, it has received 44 views. For similar materials see /class/222010/astr-1010-georgia-southern-university in Astronomy at Georgia Southern University.
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Date Created: 10/12/15
Last Time Introduction to the Solar System Lect 4 Earh Today Planet Earth Internal Structure 0 Continental Drift Atmosphere 0 Greenhouse E ect Lect4 Earth Readings in text 7173 Early Ideas about Earth The first great civilizations in the west Egypt amp Mesopotamia grew up along river basins ie at land 0 They thought the Earth was a flat disk think hockey puck surrounded by water note Earth is roughly flat over small areas Early Seafarers knew the Earth was round Lect 4 Ear h Fact and Fancy Fact Eratosthenes calculated the Earth s size ver accurately using only simple math in 240 BC North Pole Incoming sunlight Equator Lect 4 Ear h 6 Fact and Fancy 39 l Fancy Columbus set out to prove that the Earth 739 39 was round and not at Fact Every learned person in Europe already knew that Columbus thought the Earth was actually much smaller than calculated by Eratosthenes in 250 BC and China was not very far to the west of Europe Columbus was wrong The Earth As A Planet The Internal Structure of Planet Earth Magnetosphere Atmosphere 39 Hydrosphere Lect 4 Ea h Wave motion Wave motion W x c V r y M VWVWWWwVVWV fW H LO l Particle Particle motion density dens y a Pwave b Siwave P waves will travel through liquids and solids S waves are absorbed by liquids do not pass through Lect 4 Ea h 10 Mapping The Earth s Interior Analysis of P amp S waves passing through Earth after an Earthquake gives structure of Earth s interior Earthquake Note the carved paths taken by most seismic waves This is due to the increasing density of material as you go deeper into the Earth The Earth s Interior Crust 250 km thick mainly granite density 23 gcm3 T 300 K Mantle 3000 km thick mainly basalt density 36 gcm3 T 2000 K 15000 10000 Core 3000 km thick metal rich nickel iron sulfur density 10 gcm3 T N 4000 K Density kgm3 01 a O O Solid Core 1300 km thick solid metal nickel iron sulfur density 12 gcm3 T 6000 K P 4million atm 4000 2000 Temperature K O 3000 6500 3000 D 1 2 Depth below surface km The Earth s Interior Lava comes from uppermantle 9 analysis gives us some direct information of composition 0 Existence of Earth s Magnetic Field tells us that the liquid core is rotating probably faster at equator 9 Dynamo effect Lect 4 Earth Differentiation Why isn t the Earth uniform in composition throughout 0 Earth was originally molten for extended period of time o Heavier elements iron nickel uranium sank to center 0 Lighter elements silicon aluminum etc forced to top 0 Earth cooled slowly from surface down baked potato forming solid crust on surface 0 Interior cools slowly and is further heated by decay of radioactive elements 9 molten interior Crust oats on elastic mantle Lect 4 Earth Continental Drift left Animation illustrating continental drift starting 300million years ago to the present based on observed motions of the continents Continental Drift Rid dots glanoes amp major eartqukes rom 19002000 San Andreas Fault Pacific plate Cocos plate v a Locations of volcanoesEarthquakes not random Most occur where plates either collide or move apart Plates move at few cm per year fingernail pace Lect 4 Ea h 16 Lect 4 Earth When Plates Collide Sometimes one plate collides with another and thrusts it upwards creating high mountain ranges like the Himalayan mountain range Mt Everest is dark peak at left center Lect 4 Earth When Plates Graze Plates moving past one another can store tremendous amounts of energy When this energy is released it creates earthquakes often with terrible results When Plates Move Apart Africa Continental Drift Over Time If we follow the continental drift backwards the continents merge into one supercontinent 9 Pangaea 200 million 130 million years ago 65 million Present years ago 7 r r Animation showing 300 Million years of continental drift Lect 4 Earth 20 10 What Causes The Plates To Move Ocean h ench continent Ocean ridge D mg con nem Sh nMng Convection Large temperature dt erences topbottom generate currents hmnnk 7chch cool air DAY TIME NIGHT TIME 11 100 Altitude km U C Structure of the Earth s Atmosphere Ozone layer 39 r 7 7 Density decreases steadily with altitude Temperature more complicated Ionosphere partially ionized by sun Lots of electrons make it a good conductor AM radio waves bounce off carrying signal over horizon Ionosphere Mesosphere enal punor OSAl1 eJSJnSSSJd Clouds Troposphere convection is important 39 Hot air rises cools amp descends creating Weather zoned I Troposphere I 1 Weather wmds clouds etc 150 200 250 300 Very turbulent which39is Why telescopes Temperature K are located on mountain tops Lect 4 Earth 23 The Ozone Layer Lect 4 Earth 24 12 Destruction of Ozone T he Antarctic Hole Lect 4 Ea h Each Spring in Antarctica low circulation induces a vast cloud of ice crystals that accelerate the destruction of ozone by CF Cs A giant hole with 50 ozone reduction is created Other holes are known CF Cs are largely phased out It may take decades for effect to disappear Why is the Sky Blue Sunlight Earths atmosphere Red light Blue light Lect 4 Ea h Blue light is scattered much more than red light by molecules in the atmosphere Blue light appears to come from all directions in sky Red light is seen only from direction of sun Blue light di uses through sky 9 it looks blue 13 The Greenhouse Effect Not all visible sunlight reaches ground I I Escaping Vlsrble infrared sunlight radiation Most does and is absorbed by rocks soil amp plants 9 heats them Absorbed visible photons are reemited Re emd as infrared IR photons sunlight Some IR photons absorbed by molecules in the atmosphere C02 amp H20 before they can escape the Earth and reemitted back to ground amp atmosphere This trapping of extra solar energy has made the Earth 40 Celsius warmer 40 C 60 F Most of Earth s Surface would be frozen wo Greenhouse Ejj 2e7ct C0 Parts pm Million by anum PPMV allllans at Mom Tons 340 Global Warming co Concentrations The concentration of CO2 in the Earth s atmosphere has increased quite a lot over last 200 years with biggest jump after 1950 Primary cause coal burning during early Industrial Revolution amp coaloil burning 200 Carbon Emissions to generate electricity since Fowl ugly GI c landvuseClsnnge G 3 14 7 1 I aww omy of 1 Lecture Infrpdy an f0 N0 readings in textbook Today Introduction to the Solar System Assigned readings in text 11 21 2324 31 Thin s visible n the night sky Stars Constellations Some constellations are better matches than others5 The Constellation Orion The Hunter left Otical image of Orion a prominent constellation visible in Winter right Connect the dots and see the Hunter as imagined by the ancients note Greek letters denote stars from brightest a to faintest K 6 Stars in most constellations are unrelated Angular Size and Angular Distance Angular size the angle subtended by an object e g moon or sun Angular distance the number of degrees separating two objects Constellations Are Not Permanent All stars are moving around the Milky Way galaxy in nearly circular orbits They do not appear to move because they are so very far away Wot measured until 1838 As a consequence all constellations are slowly changing with time Q On average a star appears to move 01arcsecond peryear How many years would it take to change its position in the sky by 1degree Painting of a bull made by unknown artist 16000 years ago in a cave near Lascaux France Many similarly beautiful paintings adorn walls of these recently re discovered preh istoric sites Some may represent constellations Michael Rappenglueck U Munich The Pleiaes ee Sisters Close to the constellation 39 Taurus the Bull are 10 Why the sky changes during the night lookmg northward Why the sky changes during the night Polaris north celestial pole 7 77 s celesktiaLegUaIOr 4quot 7 g v quot south pole gt x y if w o V south celestial pole note Earth rotates westtoeast stars appear to rotate eastt0 west 12 Why the sky changes from night to night 9The starsconstellations you see on a Winter night are not the ones you see on a Summer night Why mg Pisces WW5 At midnight at your Taurus Apr 2i 939 2 location the Sun IS ASgm 65quot an on the other side of Nam 1 u Gm W 2 53m 2 Aug 2 4a 2 the Earthquote below NW 21 1 your feet i Hm 1 w Sagiilauus I June D 2 Jam When you look up in x v y 27 the sky at midnight on Jan 2 x quot Euhsavlw39Wm mMzw January 1st you are my 5 2quot M 2 Apr 21 mm looking towards a 39 a r quot quot1 5 9539 WWquot mm M NM 2 very different direction Cancer Aug 2i on Augus 1st 1 0c 2i Scornms Lea y I iniigusg ezsm e Sept 2 vim H You Will see different groupings of stars Answer The Earth orbits the Sun 13 Things visible in the night sky Planets Planet means Wanderer If you would watch the skies regularly for a week or so you would quickly notice that the planets move with respect to the stars Sometimes they change direction Casmr 0 I u 3 u c januar v 1 December I 3 y April 1 5 r Fubrum39y 15 F Own7 V A The Solar System An Overview Early astronomers knew Sun Moon Mercury Mars Venus Jupiter Saturn plus comets amp meteors Our Solar System consists of 0 One Star the Sun Eight Planets Dwarf Planets Pluto is one of these 135 Moons 0 gt1 00 000 Asteroids VIinor Planets many many many Comets Debris spacejunk Mercury 4 Venus x The San amp Planets Relative Sizes Jupiter Uranus Overall Layout of the Solar System Asteroid belt The planet diameters are n0t to scale in this diagram Note that Pluto s orbit is not in the same plane as the other planets19 Overall La out o the Solar System View from above Looking down on the solar system showing the nearly circular orbits of the major planets the location of the asteroid belt and the Kuiper Belt a swarm of icy bodies orbiting the Sun in the same sense as the planets counter Clockwise Question Where is Pluto in this diagram View from the side Notice that the planets asteroids and even the Kuiper Belt not shown all orbit the Sun in the same plane 20 1O What is a Planet One De nition Terrestrial Planets Mercury Venus Earth amp Mars Jovian Planets Jupiter Saturn Uranus Neptune Terrestrial Planets Jovian Planets close to the Sun closely spaced orbits small masses small radii predominantly rocky solid surface high density slower rotation weak magnetic elds few moons no rings far from the Sun widely spaced orbits large masses large radii predominantly gaseous no solid surface low density faster rotation strong magnetic elds many moons many rings The Planets Are Roughly Grouped in 2 Families 11 Planets within a family can be quite different Example A few differences among the Terrestrial Planets u ler s First LW quotAl 23quot 1111 1 l EllU Mh Astronomers had thought that orbits had to be perfectly circular as the heavens were perfect Even Galileo thought that orbits are circular At left is a very elliptical orbit The planets orbits are not this squashed Most are very close to being perfectly circular 24 12 I 39 y x f r M o J1 R x quot 1 Move the two foci further apart and the orbit becomes more squashed Move them closer together and the orbit becomes more circular Elliptical vs A circle is a closed curve such that each Circular Orbits point is the same distance from the center V xr r An ellipse is a closedicurve suchithiatiea ch point is the sum of the distances om two centers called foci singular focus folcus2 l aius vector Orbit of Halley s comet and its dust trail S MMMF wrst Sun Elliptical amp Circular Orbits in the Solar System The orbits of the planets are technically ellipses though very close to circles Comets and a few asteroids on the other hand can have highly elliptical orbits 13 Determining Basic Properties Distances How far away are the planets from us or the Sun 1 au 1 Astronomical Unit distance from Earth 9 Sun 150 million km 15 X 108 km 397 i iirlll j in lean Determining Basic Properties Distances Distances t0 the Planets in units of an A U using Kepler s 3rd Law P2 years d3 au Orbital Period years Distance from Sun au 14 Determining Basic Properties Distances To use Kepler 53rd Law we need to know au to high accuracy At closest approach Venus is 03 au away from Earth By bouncing radar waves off Venus and timing return gives 03 au 45 million km 9 l au 150 million km l Rs mefl 39 0393 A39 39 Question how long does it take for the radar wave to travel to Venus amp back 300seconds 5minutes 29 How do we measure Sizes of planets We can easily calculate a planet s diameter if we know its distance d and angular size in arcseconds Example For Jupiter 1 42 au amp 6 468 arcseconds What is Jupiter s diameter in km Answer 143000 km 30 Atmosphere finish Seasons Eclipses Tides The Moon s Origin Textbook 31 32 35 3 7 84 1 Lect 5 Ear h The Earth 5 Magnetic Field Eddy currents in the molten metal core of the Earth create a weak magnetic eld that extends far into space Rotation of Earth also helps generate this eld When Earth s core cools and solidi es in the distant future this eld will mostly disappear The North amp South magnetic poles wander I5miles during a given year Every 200 000 years or so the North amp South poles actually switch I nothing much appears to happen to living things though Birds turtles amp some insects use the Earth s magnetic eld to navigate Th e M agn etosph ere The Magnetosphere is the Earth s magnetic atmosphere It extends far from the Earth s surface and de ects the solar wind a highspeed stream of charged particles emitted by the sun and saving our bacon MAGNEI39DSPHERE sow SHOCK T he Aurora Northern amp Southern Lights Some charged solar wind particles are trapped in the Earth s radiation belts Some trapped solar wind particles travel down the magnetic field lines to the N amp S poles where they collide with molecules in the atmosphere and cause them to emit light These displays are called the Aurora Aurora from the ground Aurorafmm Space Why do we have Seasons Why is it cold in December but hot in July Why is the opposite true in Australia Lect 5 Ear h The Seasons N N Not to scale 33395 39 i i Winter in Summer I the north the north N N S S Winterin Summerin the south the south Spring Begins S The Earth spins on is axis N24hours The axis is tilted 235O away from straight out of the orbital plane it poinm close to star Polaris The orientation says fixed the North Pole stays pointed at Polaris during the orbit At certain poinm the Northern Hemisphere may receive more direct sunlight while the Southern Hemisphere is receiving less direct sunlight this reverses in 6months The Seasons In Winter the Sun is lower on the surface receives more direct horizon the surface illumination is illumination more energy per less direct less energy per square square mile Days are also longer Mile Days are shorter surface amp surface amp atmosphere warm up atmosphere are cooler as a result In Summer months the Earth s The tilt of a planet s axis determines its range of Seasons as we will see as we explore our Solar System The Seasons Things visible in the night sky The Moon Image of Earth amp 1V100n taken by Galileo spacecraft from 39 million miles away in 1992 as it heads to Jupiter Lect 5 Ear h Where did the Moon come from Amazingly the Big Whack theory explains the data best especially the moon s composition and density based on analysis of rocks brought back by the Apollo missions Phases of the Moon Sunligh39 39 D D gt gt r lt7 lc Sun 1 5 b 1 gt I Sunligh 1quot 2 39 4 2 3 x F Waxing Firsl Waxing Waning Third Waning New crescen quorlar gibhous Full gibbous quarler ElESEeI lI l 2 3 A 5 6 7 8 Appearance of The Moon From Earth Lect 5 Ear h 01 em Led 5 Eavh Phases ofthe Moon 13 New Sunlight Led 5 Eavh Solar eclipses The Sun and Moon have the same angular size Occasionally the Moon can pass between the Sun and Bath coveIing up the Sun in the sky This is a Solar Eclipse Three Kinds of Solar Eclipses Total eclipse moon completely covers sun Partial eclipse only part of the sun is hidden Annular eclipse a thin ring of the sun is seen Annular Eclipse Madrid Spain baroa 2005 Cam annular comes from the Latin word for n39ng Lect 5 Ear h Solar eclipses Lect 5 Ear h Lunar eclipses Occasionally the Moon passes into the shadow cast by the Earth Lunar eclipse occurs when the Moon moves into the Earth s shadow Lect 5 Ear h Lunar eclipses This picture shows the Moon entering the Earth s shadow at the start of a Lunar eclipse Note that the shadow is not straight but curved Ancient Greeks including Aristotle noticed that the Earth s shadow is round 9 Earth must be round Lect 5 Ear h Low tide High tide Lect 5 Ear h High tide Moon new quot r quot Moon full a Spring tides Low tide Spring Tides happen at New amp Full moon ie every 2 weeks Have nothing to do with the Spring Lect 5 Ear h 1O
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