THE PLANETS ASTR 105G
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This 0 page Class Notes was uploaded by Reina Conn DVM on Sunday November 1, 2015. The Class Notes belongs to ASTR 105G at New Mexico State University taught by Jason Jackiewicz in Fall. Since its upload, it has received 29 views. For similar materials see /class/233213/astr-105g-new-mexico-state-university in Astronomy at New Mexico State University.
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Date Created: 11/01/15
Lecture 26 The Sun ll ASTR 105C The Planets April 30 2009 Announcements 1 Lab today Review for Final77 pages 195 200 2 Last observatory night tonight 3 The review session will be held Wednesday at 4pm bring questions Last time c We talked about the basic parameters of the Sun 0 Why it stays in one piece in equilibrium 0 Nuclear fusion proton proton chain c The hot corona7 cooler chromosphere7 even cooler photosphere 1 Solar Physics 11 Structure of the Sun Internal Strati cation of the Sun and Figure 143 Refer to Figure 1 The Convection Zone 0 Extends about 307 or 200 Mm into the interior 0 2 million K at the base of this zone 0 The convection transports huge amounts of heat from the base to the photosphere 0 Material expands as it rises and cools o simulation of convection1 1httpWWWsolarviewscomrawmiscconvectmpg Lm tum 25 AW 31 217179 whvluxphaw mm m mm 1 The mpexatuxe male of Lhe Sun mm depth shuwmg Lhe mnez xey ns Lecture 26 April 30 2009 3 5 The Radiation Zone 0 The radiation zone covers from 07 R sun to about 025 R sun 0 Here radiation transports the energy or photons of light randomly making their way to the surface bouncing off electrons on their way 0 They travel at the speed of light but take sometimes one million years to reach the convection zone 0 The density at the bottom is like that of gold and at the top less than the density of water 0 Its highest temp is about 7 million K The Core of the Sun 0 The core can reach 15 million K o The core rotates rigidly unlike other parts of the Sun 0 Enough energy around to allow for H nuclei to collide and overcome the repulsive electrical force and begin fusion Helioseisrnology o How do we know about the interior 0 We use the waves that are excited by convection and produce continuous innumerable sun quakes77 o The surface moves up and down in different patterns2 0 Then mathematical models give us inferences about the interior 12 Solar Activity Magnetism o The Sun s magnetic eld is generated by a solar dynamo and permeates the entire Sun 0 Rotation and internal shear of a charged plasma create magnetic elds at the bottom of the convection zone 0 Sometimes ropes of magnetic elds oat to the surface and form sunspots which we can observe Ground based telescope image of a group of sunspots3 Also manifests in the coronal loops we saw 0 Identi able at many different wavelengths of light 0 See Figure 1420 2httpwwwifahawaiiedu barnesast11006tsaassolarmodegif 3httpwwwsolarviewscombrowsesunsunspot3jpg Lmtum 26 AW 30 2009 4 5 DAILY SUNSPOT AREA AVERAGEI OVER INDIVIDUAL SOLAR ROTATIONS gt tutx via 1 Igt Luv 111 Vat le I 1A1 11 Inn quot111 u 2 m on I I II I I I I I I I I I I l IIIII III 1 II I i l i I i I I I I1 I I at 1 I an I un mm mm mu uni 1 4 mu uh uh mu nn inn mm 210 out Figuxe 2 The buttei y diagxam of the Sun and sunspot numbex 0V6 tune Activity Cycles 0 The dynamo changes 0V6 tune both in stiength end position and peuodicelly o This is known as the solar cycle o One lesult is that the Sun s magneth poles levelse evezy 11 yeazs o Anothel lesult is that sunspots Valy in fzequency and location Oven 11 yeazs 0 Sometimes theie eie exceptions to this tiend Maundel Minimum 0 Neal the beglnnlng of the cycle sunspots appeal at hlgh latltudes o Ovel tune they appeal close end close to the equetoi eventuelly not appealing et a o This behavlol ploduces a buttei y diagxam The Butter y Diagram Soulce of Flguze 2 httpcommonswhimediemgwusilmege Sunspotlsuttezllysmthgeyhipg Eruptive Events 0 When magneth elds in the etnnospheie become tvusted end stiessed they can ieleese huge ounts of enezgy Lecture 26 April 30 2009 5 5 0 Solar are explosion in the corona and chromosphere releasing UV and x rays Here are coronal loops after the are o Coronal mass ejections CME are even larger expelling mass and charged particles into space at high velocities o Granddaddy CME5 Effects on Humans and Earth Space Weather 0 Changes in the sunspot cycle do not produce noticeable changes on Earth in terms of the Sun s luminosity and radiation output 0 We are vulnerable to isolated events 0 The magnetosphere of Earth protects it pretty well but 0 Big ares induce big geo magnetic storms that can induce huge power outages on Earth They can affect satellites orbiting the planets heating them up andor slowing them down and exposing them to harmful radiation 0 Communications systems are affected Space station airplanes astronauts Why Study the Sun 0 Because it directly affects our lives through the solar wind and space weather 0 Because it helps us understand other stars and stellar evolution 0 Because it serves as a laboratory for science that we cannot reproduce here temperatures pressures density energy 0 Just because For next time 1 nal exam 4httpz m Fr m a m imagesimp M m 5httpz m Fr rm a In images Lecture 12 Spectra of Matter ASTR 105C The Planets February 247 2009 Announcements 1 Exam Thursday 2 Review session tomorrow night 7pm here 3 Some homework problems from HW5 Last time c We talked about what light can do when it interacts with matter 4 possibilities o The building blocks of matter nuclei7 electrons7 atoms7 molecules 0 Phase changes 0 We began discussing energy levels of atoms Quantitative View of Energy Levels of Hydrogen Source of Figure 1 httpwebnjitedu gary728Lecture2html 1 Radiation and Matter 11 Interpretation of Astronomical Radiation and Spectra Spectroscopy o Spectroscopy studies the intensity of light number of photons or energy at different wave lengths These are light curves 7 or spectra 0 There are generally 3 types of spectra H Continuous Broad spread of intensity over all wavelengths to Emission Discrete peaks in intensity where electrons are jumping into lower atomic energy levels OJ Absorption Discrete dips in intensity where atoms have absorbed radiation at certain energy levels and jumped to higher levels The Solar Spectrum Source of Figure 2 http mm an r r Y H 351 mm a 20479 mem y Fvthnvm 5102 7 A 7 A 7 Hume Senes Gramd Sm Encrgy chcl Diagram Lyman Senes quotyd hgue 1 aqer 1mg a mehydwgm am Lcccm 12 man 24 217179 9 a Visible Sula EnIlQV W m Wavelengm 4m gure 2 med im mm mi Continuous Spectra o A conunuous specuum comes from any body wnn c uempemcuze o The specuum onbl depends on uempemcuze and 1s conunuous 7 thermal blackbocly rar diztion 9 oz home ob JecLS o Wien s Law Hotmz objects emn mdmuo n at hxghel equencles hxghez energies N T 9 See animation 5 19 allows us we demrmme abodles mmpemtuxe Emission Spectra o Collisions m c cloud cigas change the dnecuon of moms 9 Then the daemon falls back down an emns c photon of mm 9 Example pxoblem ox Hydrogen ennssxon 9 Moms have umque ngelpxm39s ofe mlsslo n knee 9 See animation 5 1A emission 9 Example pxoblem Lecture 12 February 24 2009 4 5 Example Problem for Hydrogen Emission We see from Figure 1 the energy levels of hydrogen Let s image an electron residing in the rst excited state which has an energy of 34 eV Then it jumps back into the ground state and ends up with an energy of 136 eV In the process it must have lost 102 eV of energy by giving off a photon of light Let s compute this photons wavelength We know that energy is related to frequency by 1971 where Planck s constant h 414 x 10 15 eVs Solving for f we nd that f 246 x 1015 Hz We can nd the wavelength from the frequency by f c where c is the speed of light Solving gives 121nm 1 If you look at the electromagnetic spectrum you ll see that light of 121 nm is ultraviolet Now consider an electron that jumps from the third excited state of hydrogen to the second excited state It loses 189 eV of energy much less than the other transition so we should expect a longer wavelength photon Solving for the wavelength in the same way try it gives 657 nm Light of this wavelength is red Absorption Spectra o Incoming light in a cloud of gas gets absorbed by atoms and electrons jump into higher energy levels 0 When the electrons then lose the energy they just absorbed a photon gets emitted in a random direction not necessarily towards the observer 0 See animation 514 absorption More about Spectra o Ions also give unique identi cations Since we know the temperatures at which certain atoms become ions we get an idea of the temperature of the material 0 Molecules produce spectra of molecular bands usually in the infrared range 0 Spectra can give us the composition of many astronomical objects at least the part of the object from which light leaves Voting question Spectra Which telescope would record a spectrum that looks like the one shown Figure 3 A telescope A B telescope B C telescope C o The answer is B Lecture 1g Februcry 24 gm 5 5 5 WW mm 3 veteran o O 6 sum Li meme I V Figure 3 Example spectrum from a star Which telescope would record this spectrum 12 Doppler Shift Doppler Effect 0 We have all experienced the changing sound of an ambulance or train as it passes by1 0 Sound waves are shifted to higher frequencies shorter wavelengths as the train is coming towards you and shifted to lower frequencies longer wavelengths as it moves away 0 Moving source animation of Doppler effeth o The same thing happens for waves of light and radiation e objects moving towards an observer are blueshifted objects moving away are redshi ted For next time l EXAM 2 Read Lab The Orbit of Mercury pages 69780 339 Next Week we start talking about telescopes http www fouxmllab chcshipsoundsdoppler an QhLLp www felsted comuppleexrdopplex html Lecture 21 Weather and Climate of Terrestrial Atmospheres ASTR 105C The Planets April 9 2009 Announcements 1 HOMEWORK 9 DUE TODAY 2 LAB TODAY Surface Water Features on Mars77 3 Review session Monday night7 7pm7 here 4 Exam Tuesday Last time c We talked about atmospheric science strati cation o The greenhouse effect c How radiation interacts with gases in the atmosphere 1 Atmospheric Science 11 Weather Basics LargeScale Circulation 0 Imagine a non rotating Earth 0 Since the equator is warmer than polar regions7 warm air will ow on top from the equators toward the poles 0 Then there is a cooler air ow underneath this Figure 1013 0 But the Earth does rotate7 and then we have to take into account the Coriolis effect Coriolis Effect 0 A pseudo force depends on reference frame of observer 0 Dem onstration1 1http wwwyoutubecomwatch7vmCPsOdQOYU Lecture 21 April 9 2009 2 6 o What the Coriolis force does is split the circulation cells into smaller cells Figure 1016 0 Since the equator rotates faster than other regions o It diverts north south movement into east west movement and gives the large counter clockwise storm patterns in the northern hemisphere 0 Like this2 0 Figure 1015 What Causes LongTerm Climate Change 0 On scales of millions of years 7 Solar brightening The Sun is brighter than it was early in its lifetime and could cause objects to be warmer 7 Axis tilt changes 7 Re ectivity of atmosphere changes 7 Amount of gas Loss or Gain of Gases 0 We know that volcanic activity is the source of most atmospheric gas7 such as water7 carbon dioxide7 nitrogen and sulfur gases 0 There are also sublimation processes and micrometeorites 0 Many ways to lose atmospheric gas 7 condensation rain 7 chemical reactions oxidation rusting these 2 are renewable 7 impacts from bombardment 7 solar wind stripping from lack of magnetic eld 7 getting above the escape velocity thermal escape Thermal Escape of Gas 0 A planet7s size determines its escape velocity 0 The temperature does too 0 So does the type of gas H and He can easily escape o How do we compute these things Example problem 1060 2http enwikipediaorgwikilmage L0wpressuresystem verlcelandjpg Lecture 21 April 9 2009 3 6 Example Problem 1060 The escape velocity from a planet is derived in Mathematical lnsight 44 in the text It is determined by equating the kinetic energy of an object with the gravitational potential energy of the planet 12mU2 GMmR a u escape 2GMR where M and R is the mass and radius of the planet a For Venus we are interested in the escape velocity above 200 km The radius is about 6000 km so we will take R 6200 km Its mass is 487 x 1024 kg So we have vescape 2667 x 10 11487 x 10246200000 102 kms b For atoms and molecules in the atmosphere their velocities are determined by the local tem perature and this is called the thermal speed vthemal 2kTm where k is Boltzmann s constant T is the local temperature and m is the mass of the particle We are asked to consider hydrogen and deuterium at temperatures of 350 K So uthemmlhyd 2138 x 10 23350167 x 10727 24 km2 115mm 138 x 1023350167 x 10727 17 km2 c We see that at these heights and temperatures neither hydrogen nor the heavier deuterium can escape Venus s atmosphere We learned that hydrogen did escape this way so it must have been either when the atmosphere was hotter or at a higher height than that here 2 Atmospheres of Speci c Planets 21 The Moon and Mercury The Moon and Mercury 0 Today these two objects only have a very thin exosphere 0 Only source of gas is micrometeorites o Likely long ago had gas but small size allowed it to escape c There is some evidence of water ice on the Moon and Mercury in craters near the north and south poles 22 Mars Mars 0 Quite different than Mercury today even though its less than twice as large 0 Very thin atmosphere with low pressure liquid water would either freeze or evaporate im mediately 0 Carbon dioxide of low density not enough to make greenhouse effect work Lmtum g1 Apml 9 gm 4 s Mars Global Dust Storm June 26 2001 September 4 2001 Hubble Space Telescope WFPCZ NASA J Bell Cornell M Wolff Asst and the Hubble Heritage Team ST URA STScIPRCmsi Seasons on Mars 0 The southem hemisphere experiences veiy extreme seasons compared to the northern hemie spheie due to tilt and eccentricity of orbit o In Winter the pole accumulates carbon dioxide ice and takes it out of the atmosphere 0 This drives stiong winds from the summer poie to the winter pole and creates big dust storms o The scattering of iight by this dust ieaves the atmospheie with a yeiiowish brownish color Martian Dust Storm Refer to Figuie 13 Mars Has Changed 0 Mars probably had a wet and waim ciimate 3 biiiion yeais ago 0 Dense atmospheie fiom voicanic activity e but it iost this atmosphere 002 0 Most likely because it iost its magnetic eld as the Cole cooied o This aiiowed the solar wind paiticies to stiip the planet of its gas 0 The Water was broken apart by ultraviolet radiation and the H atoms theimaiiy escaped into space 0 Oxygen atoms Iusted the surface Lecture 21 April 9 2009 5 6 23 Venus Overview 0 Primarily a 002 atmosphere very dense and high pressure 0 Slow rotation no Coriolis effect 2 large circulation cells which transports equatorial heat to the poles very efficiently o Clouds of sulfuric acid in the cooler troposphere o No water 0 Why so different than Earth even though the sizes are similar What Happened c We would expect that outgassing from volcanoes provided the same amount of water and carbon dioxide to Earth and Venus c We know where our water went a oceans 0 Then carbon dioxide dissolved into the water as it readily does a limestone 0 Venus lost its water to space from the solar wind and ultraviolet light interactions 0 But the imbalance came about because of its proximity to the Sun Greenhouse Effect on Venus 0 Venus is intrinsically warmer due to its location 0 Water gas is a greenhouse gas so evaporation due to the temperature rise would increase the temperature even more 0 This effect would spiral out of control runaway greenhouse effect 0 Water would eventually disappear o No rain to fall down and make oceans so the carbon dioxide stayed in the atmosphere 0 See again how lucky we are 24 Earth Why are Nitrogen and Oxygen in the Atmosphere 0 We have 77 N2 and 21 02 o Nitrogen is a product of outgassing but oxygen is not So why do we have if 0 Us Well plants not us but living things built up oxygen in the atmosphere over a couple billion years 0 Read pages 317 321 about Earth s COZ cycle and human in uence of the climate Lecture 21 April 9 2009 6 6 Summary 0r Mars7 Venus7 Earth Summary For next time 1 Next Thursday We will talk about Jovian planets 3httpastronomynotescomsolarsysevmtempgif Lecture 23 Jovian Planets H ASTR 105C The Planets November 18 2008 Announcements 1 HOMEWORK 10 DUE TODAY Last time c We talked about general characteristics of Jovian planets 0 Mostly H He and hydrogen compounds 0 They rotate fast 0 Jupiter has H gas liquid H metallic H and rocky core 1 Jovian Atmospheres 11 Jupiter Jupiter Composition 0 Jupiter s interior is mostly H and He but it has different layers or zones 0 These are distinguished by different phases of the hydrogen 0 Its crust is gaseous H because it s cold and not dense 125K 0 Below the crust it is warmer 2000K and is liquid H 0 Its mantle is hot and dense and the H is metallic solid conducting o The core is very hot and dense and we have rock metals H compounds 0 Cutaway of Jupiter s interior1 Internal Heating 0 Jupiter has a lot of internal heat but loses a small fraction because it is so big o Accretion differentiation and radioactive decay are not enough to explain its large heat reserves 0 1t heats up by contracting 2 cmyear 0 Convert gravitational potential energy to thermal energy 1http enwikipediaorgwikilmageJupiterjnteriorpng Lecture 25 November 18 2008 Ju pitar 395 atmosphere first lir39Iect measurement 2 from Salilea probe I ammonia G39II TLIS wig g I ammon Ia39sulfur clouds H In L N d w III In 3 VI Ill L Q 2 L ll u VI 15 E 14 Iquot Figure 1 Strati cation of Jupiter s atmosphere Weat her 1Inu EIJU DD a Iml l o Rememloer7 next to H and He7 C7 07 and N are the most common elements7 that s Why atmospheres typically have compounds like CH47 NH37 and H20 0 Atmosphere is somewhat similar to Earth s temperature strati cation o Gases rise by convection and condense into clouds in 3 layers in the troposphere 7 Lowest layer cooler water droplets 7 Then ammonium hydrosul de 7 Top layer ammonia Jupiter7s Atmosphere Source Of Figure 12 httpWWWbritanninacornEBcheckedtopiceart30840371526Pro leofeJupiterseatmosphere as deducedefrome ace elerometere dat a and Storms 0 Fast rotation and Coriolis effect creates many cells or hands of circulating air Lecture 25 November 18 2008 3 6 o North south bands turn into east west stripes o The reddish colors are deeper ammonium sul de and the upper clouds are white ammonia and these rise and fall to drive global wind patterns 0 Figure 119 o The Great Red Spot is a high pressure hurricane gt 3 centuries oldll o No seasons on Jupiter because no axis tilt and strong internal heating Magnetosphere o Jupiter s magnetic eld is 20000 times stronger than Earth s has all the ingredients 0 Very effective at blocking the solar wind and trapping charged particles 0 Gives bright auroras 0 Also has effects for the moons of Jupiter Rings 0 These are so much fainter than Saturn s that it took 400 years longer to discover them 12 Saturn Overview 0 Similar interior to Jupiter 0 Thicker layer of outer gas because not as much pressure as Jupiter Saturn loses more heat than it gains from the Sun7 so it must be generating a lot of heat like Jupiter 0 But it s not shrinking7 it is differentiating helium liquid rain Same atmospheric properties as Jupiter7 but since its colder the 3 layers are closer to the surface 0 Similar rising and falling bands of air with winds faster than Jupiter s Big axis tilt but no real seasonal changes because of internal heating 0 Weaker magnetic eld so smaller magnetosphere Rings SourceofFigure 2 http an norm lleCassinieC P M 1quot N Saturn Discoveries V html Lecture 93 Nougmbn 18 008 4 6 Figure 2 An image of Saturn s rings from the Casslnl spacecraft Details of Rings 0 The rings look continuous but there are many concentric individual rings 0 Mostly water ice very reflective 0 Made up of tiny to boulderrslze particles each one following Kepler s laws 0 Frequent collisions take place and keep the rings in a very thin plane a few 10s of meters thick 0 Cap rnoons create some space in between rings Pan and Daphnis2 0 Also some extra force from real rnoons creates gaps Cassini division and wavelike features Why Are There Rings 0 Around the zone of the rings the balance between selfrgravitatlonal forces and tidal forces would rim 394 rt 1 r m H 39 39 39 moons o Orwhen the Jovian planets were born leftover ice and dust planetesirnals never accreted but remained in the ring region 7 but they are too small to have lived that long 0 So the ring material must constantly be renewed and supplied 7 likely by numerous small gap rnoons that get grinded down 0 Figure 1131 thtp photooumaljpl nasa govipegvledPlhoammedest Jpg Lecture 25 November 18 2008 5 6 13 Uranus Overview 0 Image3 0 Pressure not high enough to form liquid or metallic hydrogen 0 Gaseous outer layer with hydrogen compound mantle rock and metal core 0 No internal heat production since it does not emit any 0 Very cold atmosphere so we are not sure if the 3 layers exist they are buried in the opaque atmosphere 0 Strange weather no clouds or banded structures like the others but possibly storms in the atmosphere because of seasons weird axis tilt 0 Weak eld but largish magnetosphere because the solar wind is weaker this far away 0 Rings are slightly tilted and eccentric discovered in 1977 14 Neptune Overview 0 Pressure not high enough to form liquid or metallic hydrogen 0 Similar to Uranus 0 Very blue because of methane in atmosphere4 0 Emits a lot of energy so it might be contracting like Jupiter still a mystery 0 Very cold atmosphere so we are not sure if the 3 layers exist they are buried in the opaque atmosphere 0 Similar banded atmosphere with high pressure storm The Great Dark Spot775 0 Large axis tilt but no seasons because of internal heating 0 Weak eld but largish magnetosphere because the solar wind is weaker this far away 0 Rings appear as partial rings due to dust For next time 1 Malynda will teach us more about Mars than you ever thought you7d know 2 We will talk about the Jovian moons 3httpuploadwikimediaorgwikipediaCommons11bUranusJoyagerjjpg 4httppdsjplnasagovplanetsimagesfullneptunefullnepjpg 5httpuploadwikimediaorgwikipediaCommonsEVS1Neptunedarksp0tjpg
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