Stel Gal AstrCoReq ASTR 1211S
Stel Gal AstrCoReq ASTR 1211S ASTR 1020
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Popular in Astronomy
This 83 page Class Notes was uploaded by Dr. Deion Conroy on Monday October 12, 2015. The Class Notes belongs to ASTR 1020 at Georgia Southern University taught by Sarah Higdon in Fall. Since its upload, it has received 36 views. For similar materials see /class/222012/astr-1020-georgia-southern-university in Astronomy at Georgia Southern University.
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Date Created: 10/12/15
Lecture 1 Overview Prof Sarah Higdon I Q I I I I I I IDIIIII Lecture 2 Profs H gdo 1 Lecture 1 Overview Course Structure Astr 1020 WebSite Lectures Tues amp Thurs Cover Essential course material quizzes Textbook Universe Stars amp Galaxies Roger Freedman amp William Kaufmann III Freeman 3rd Edition Well Written amp tied to lectures Lecture 2 vas Hl dun Last Time I What is Astronomy What is Science I The night sky overview l Why the sky changes I During the night I From night to night I Eclipses I Seasons why is winter coldsummer hot i I IIIQIQII Lecture 2 vas Hl dun 1 Lecture 1 Overview Free Physics and Astronomy Tutoring Room 2023 in MathPhysics Building I MonTuesWed 5pm7pm I Thur 6pm8pm I I I is I I I I LeotureZProfS Higdon I H I 39J I It I Today Electromagnetic Radiation Goals of this section 1 understand what EM radiation is amp how it transports energy across space 2 understand the different portions of the EM spectrum Xray ultraViolet optical infrared radio 3 understand how they are different 4 Blackbody radiation 7 what it is and how it gives temperatures 5 Doppler Shift 7 what it is and how it gives speed I I I I I I I I IIIQIII Lecture 2 Profs Higdon 1 Lecture 1 Overview The Universe is big amp life is short Leciuve 2 vas Hi dun Warning We assume that physical laws in distant objects the same ones we observe on Earth I I i U I Uniformity of Nature I Leciuve 2 vas Hiudun E 1 Lecture 1 Overview l Many examples of waves can be found in Nature ex Sound waves ocean waves Lecture 2 Prof S Higdon Propertiesiof Waves Waveiengm A Iri xmphmde Undistwbed Trough State Direction of wave motion 1 Wavelength A 7 distance between two creststroughs 2 Amplitude A 7 how high wave is 3 Speed v 7 how fast the wave moves 4 Period P 7 time for passage of two crests or two trouggs 5 Frequency f 7 number of crests or troughs that pass by in one second eg 20 per second I Lecture 2 Prof S Higdon 1 Lecture 1 39 Overview Properties of Waves Wave B Leduvez F39VDVS Hlmlun ElectroMtighetic Waves II quotgm All charged particles modify space by creating an Electric Field E This E eld extends through all space strongest near the particle H F m weakens the further away you are H m All charged particlesfeel the E elds of each other 5312 chargedparticles communicate 39 electric forces this way I l I mam 239 Wm V we mng Leduvez F39VDVS Hlmlun 12 I I I 1 Lecture 1 Overview flecti oMagn etic Waves III Distant Vibrating arge charge iquot J Wave Lecture 2 Profs Higdon How fast are ElectraMagnetic waves a ElectrOmagnetic radiationwaves travel at the speed of light 7 c Lecture 2 Profs Higdon 1 Lecture 1 Overview Light is ElectraMagnetic Waves Skin feels Eyes see Damages Damages this range this range skin T155119 mule Inhaled Visible Ultraviolet x ray Gamma my I l 39 43x10 75110 Frequency Hz I Wavelength lnm mo 4039 I I I I Lecture2 Profs ngdon I I I I I I I I 4m 5n m amy Aimmnvam rumle l ppm Lecture 2 Prof S H 1 Lecture 1 Overview Some wavelengths of EM radiation pass through Earth s atmosphere eg optical amp radio 9Atmosphere is transparent to these wavelengths 1 I Much of the EM spectrum is absorbed by the atmosphere eg ozone other molecules This is a good thing Lecture ZProfS ngdon I i I Q 17 LightEM radiation can travel through the vacuum of space amp atm0sphere mostly water ever beenscuba divingsnorkeling yglass esh X rays amp gammarays m buildings radio waves Q What medium does EM use Lecture 2 Prof S ngdon A Nothing 18 IIIQIQI 1 Lecture 1 Overview Bi Particlelike Energy of A Photon The energy of EM radiation is related to its frequency E h f Where h is a small number called Planck s Constant h 663 X 103934 I s Because frequency amp wavelength are simply related speed fX A we can also write the energy as Ehx speed hc A T IllMll Lecture 2 Profs Higdon iQiampiAi Time Consider two EMWaves A and B A has A 2000 nm while B has A 500 nm 1 Which photon carries has more energy a A b B c same 2 By what factor a 025 b2 c4 d8 3 Which photon could you see with your eyes a A b B c both d neither 1T IllIIII Lecture 2 Profs ngdon I I I I4 I I I I 1 Lecture 1 Overview Radio Photons amp Snowflakes Compare the energy of a falling snow ake to the energy ofa 21cm radio photon emitted from the Andromeda Galaxy Answer One way is to collide them together Lecture 2 vas Hman 1 Lecture 1 Overview Temprature and Motion T 10 degrees 1 0 Q 0 I I I in I I I I IIIIJIII Lecture 2 Profs ngdon Temperature is a measure of average speed T 100 degrees T 400 degrees O a 0 0 Q 94 0 Y is m in IIIQIIII Lecture 2 Profs ngdon 1 Lecture 1 39 Overview EM spectrum and Temperature the resulting spectrum of EMradiation has a special shape Blackbadfv Radiation mm lt ii in mm mm erl MrNVHH I Nate explaining the shape of this curve Blackbadfv curve was thefirst success ofquantum mechanics in the late 1890 s Max Planck won the Nobel prize for this Leduvez vas H Edun I I I 394 I I 25 I Blackbody curves and temperature Consider four Blackbodies with different temperatures but same size mm SPcmNm A mumme 3 I I I Leduvez vas Higdun I I I I 1 Lecture 1 Overview Wien s Law There is a simple relationship between T and A of peak 39 Wie Law Lemme IPvuvs H gdun I I I II I I I I m 71 Temperatures using Wien s Law ma a F ruzx L I w mesa 39 H 7 mx I I m I I Lemme IPvuvs H gdun I I I I I I I I 1ltgt Lecture 1 Overview ll F Wien s Law in Practice I What is the maximum wavelength in Angstroms wavelength where Planck spectrum is at its peak that the sun radiates at I Compare this wavelength to your maximum wavelength assuming you are a perfect blackbody I What part ofthe EM spectrum do you radiate at Does the sun radiate at I I I I I I I 29 ll 39 Stephan s Law The Total Energy A Blackbody Radiates I I I Example Double the temperature iJ Flux Wm 9 24 2x2x2x2 I 16 times greater Lecture szis Hludun I I I I I I I I an 1 Lecture 1 Overview Stefan s Boltzmann s Law I raise the temperature in the filament of a 100W light bulb by a factor 3 how many watts is it now radiating I This is equivalent to how many 100W bulbs IIIIEIII Lecture 2 vas Hl dun Lecture 2 vas Hludun 1 Lecture 1 Overview I I I I I I I I Lemmeszvs ngdun I I I I I I I Astronomers Use The Kelvin Temperature Scale Lemmeszvs ngdun I I I I I I I 1 Lecture 1 Overview The Doppler Effect recall your experiences with passing retrucks with sirens or trains 9 39siren s pitch goes up ie higher frequency as it approaches 9 siren s pitch goes down lower frequency as it moves away This is the Doppler E ect therchanging of pitch frequency due to motion of the Source I I II m a WWW I I n I 35 IIIIIIUI Doppler Effect 0 Lemma szis gun 1ltgt Lecture 2 vas H Edun Lecture 1 Overview The Doppler Effect 37 IIIIIII gtWquotJ Lecture 2 vas H Edun 4 True ofFalse EM radiation can travel through a vacuum Sound waves can travel through a vacuum UV radiation has larger A than radio radiation UV waves carry more energy thanradio waves 3 IliOIII 1 Not the National Geographic photo of the year remember to be skeptical Lec 5 Prof Sarah Higdon 1 u walk lawn 1quot mmmid Previously Telescopes Part 1 Telescopes have two primary inctions 1To collect and concentrate weak signals from ace ie optical photons Xray photons radio photons etc 2 Allow us to see structure in astronomical objects 3 Refracting telescopes use lenses to bring light to a focus 4 Re ecting telescopes use mirrors to bring light to a focus 5 Chromatic aberration is the inability of a lens to bring light of different colors to a single focus 6 Nearly all modern telescopes used by astronomers are re ectors Advantages of Re ectors 39 Ve large mirrors can be built and supported with no distortion 39 Segmented Mirrors Build big mirrors out ofmany smaller mirrors 39 fewer light losses 39 no chromatic aberration Lec 5 Prof Sarah Higdon Telescopes part II 7 Light gathering power is proportional to the collecting area mirrorlens diameter2 8 The Angular Resolution AR is the smallestf eature that can be distinguished on an image measured in arcseconds AR 000025 A dm 9 The earth s atmosphere limits AR to N1 in the optical for most observatories 10 Adaptive optics A0 is a technique that tries to correct for the loss of AR due to turbulence in e atmosphere by rapidly deforming a exible mirror 11 AO works best in the infrared easier and generally works over small regions of sky 12 Better yet is to put your telescope above the atmosphere but it is very expensive 13 The eye is ofvery limited use in astronomy not designed for faint light levels cannot integrate a signal limitedwavelength coverage the eye can be fooled 14 Photographic plates were a big improvement over the eye 39ntegrate for hours to build up a faint image image large region of sky not very efficient only N2 of photons are captured narrow wavelength range 15 Photographic plates have been largely replaced by CCDs ry efficient N70 of photons are captured wide wavelength range easy to put into computers limit to small regions of sky Lec 5 Prof Sarah Higdon TABLE 51 Astronomy at Many Wavelengths General Considerations Common Applications Chapter Reference Radio Infrared Visible Ultmvialet X my Gamma my Can penetrate dusty regions of interstellar space Earth s atmosphere largely transparent to these wavelengths Can be detected in the daytime as well as at night High resolution at long wavelengths requires very large telescopes or interferometers Can penetrate dusty regions of interstellar space Earth s atmosphere only partially transparent to infrared radiation so some observations must be made from space Earth s atmosphere transparent to visible light Earth s atmosphere is opaque to ultraviolet radiation so observations must be made from space Earth s atmosphere is opaque to X rays so observations must be made om space Special mirror con gurations are needed to form images Earth s atmosphere is opaque to gamma rays so observations must be made from space Cannot form images Radar studies of planets 2 9 Planetary magnetic elds 11 Interstellar gas clouds and molecules 18 Galactic structure 23 24 Galactic nuclei and active galaxies 23 24 Cosmic background radiation 27 Star formation 1920 ec stars 20 Center of the Milky Way galaxy 2 3 Active galaxies 24 Large scale structure of the universe 25 27 Planets 7 14 Stars and stellar evolution 17 20 21 Normal and Active Galaxies 237 24 Large scale structure of the universe 25 Interstellar medium 19 Hot stars 21 Stellar atmospheres 16 Neutron stars and black holes 22 Active galactic nuclei 24 Hot gas in galaxy clusters 2 5 Neutron stars 22 Active galactic nuclei 2 4 Copyright 2005 Pearson Prentice Hall Inc Today Our Nearest Star The Sun Lec 5 Prof Sarah Higdon Lec 5 Prof Sarah Higdon Mercury Lec 5 Prof Sarah Higdon Satu rn Lec 5 Prof Sarah Higdon HM in quotw H i 34L 4 Lec 5 Prof arah Higdon Earth vs the Sun What Powers The Sun The Sun generates a large amount of energy Le 39 x 1025 Watts At a distance of lSOmillion km from the Sun ie l AU each square meter of space receives 1400 J of energy each second equivalent to 14 lOOWatt bulbs Fact Studies of the fossil record of life on Earth indicates that the Sun s energy output has remained nearly constant for at least 3billi0n yrs if the Sun were grew significantly hottercolder Earth s climate would be drastically different leading to large scale extermination Lec 5 Prof Sarah Higdon Gravitational Collapse KelvinHelmholtz Contraction huge weight of Sun s outer layers causes Sun to contract and heat up ie compress gas gt Temperature rises eg pumping up a bicycle tire Problem only last for 25 million years Lec 5 Prof Sarah Higdon Chemical Burning Ordinary burning involves chemical reactions that re arrange the outer electrons of the atom but do not effect the atom s nuclei Not much energy released per atom 103919 J per atom Is this suf cient to power the Sun Luminosity of Sun 39 X 1026 Js How many atoms per second need to be burned The mass of the sun is 2 X 1030 kg assume it is made entirely of Hydrogen mass Hydrogen atom 1 7X103927kg How many atoms are there How long would this energy supply last Lec 5 Prof Sarah Higdon 13 Chemical Burning Lec 5 Prof Sarah Higdon 14 Energy Generation in Stars The high pressure amp temperature at the Sun s center mean that particles will be colliding very violently i e high speea This realization provided the main clue to what powers the Stars Proton 0 M Proton Lec 5 Prof Sarah Higdon 15 Energy Generation in the Sun Neutrino Proton Positron o Proton Deuteron Lec 5 Prof Sarah Higdon 16 Fusing Hydrogen to Helium The ProtonProton Chain 3 y rays Eiectron A W W Positron Wm Neutrino Proton Ii Deuteron Protons quotl Helium3 o u 1 5 Helium4 ii w a N E m Deutemn Neutrino y rays awquot Proton a ways Electron Copyrighl 2005 Pearson Prentice Hall inc Step 1 twice 1H 1H 9 2H v et e r e 92 highenergyphatans Step 2 twice 2Hdeuteron 1H 9 3He highenergyphatan Step3 3He 3He 9 4He 1H 1H Net Reaction 41H 9 4He photons energy 2 neutrinosescape Lec 5 ProfSarah Higdon 17 Nuclear Fusion Albert Einstein 1905 Special Relativity see later in course E ch E energy in joules M mass in kg 0 The speed of light 3 x108 ms Coupled with Arthur Eddington s theory that the center of the sun is very hot and Robert Atkinson suggestion that under these extremely hot and dense conditions Hydrogen could fuse to Helium Lec 5 ProfSarah Higdon 18 Hydrogen Fusion 4 X1 H gt 4He neutrinos gammarays Difference in Mass 4 hydrogen atoms 6693 X 1027 kg 1 Helium atom 6645 X 10 kg Mass lost 0048 X 1027 kg 07 E mc2 48X1029kg X 3x103 ms3 43 X 103912 J Lec5 ProfSarah Higdon 19 How Many Tonnes of Hydrogen are fused to Helium per second For every kg of Hydrogen 07 ofthis mass is converted into energy during the fusion to Helium E mc2 0007 kg X 3 X 103 ms2 63 X 1014 J Amount of H 39 X 10 63 X 1014 Jkg 6 X 1011 kgs 600 million metric tonnes of hydrogen fused to Helium every second Lec5 ProfSarah Higdon 20 How Long could The Sun Fuse Hydrogen at this rate Fuses 6 x 1011 kgs Mass Sun 2 x1030 kg Could fuse hydrogen for yrs Lec 5 Prof Sarah Higdon 21 Applying The Scientific Method To The Sun Can not send a probe so need to Observation Theory construct a model t Copyri eeeeeeeeeeeeeeeeeeeeeeeeeeeeee 0 Lec 5 Prof Sarah Higdon 22 11 The Sun is Constant The Sun s diameter has not changed appreciably over the 4OO years we ve been observing it with telescopes Records of solar eclipses goes back 4000 years Egypt Sumer China Greece MesoAmerica This implies that the Sun has had the same angular size as the Moon 12 degree during this time The fossil record shows that over very longer timescales the solar radiation has been roughly constant Pressure out Gravity in The Sun is in a state of Hydrostatic Equilibrium at every point gravity is balanced by the outward pressure of the hot gases 23 Hydrostatic Equilibrium Pressure from water above the fish Sun is not undergoing any drastic changes Fossil Record This means the sun is in both hydrostatic and thermal equilbrium I I 1 l quot 3 quotquotquoty quot 1 5 L 7 Pressure Xr eight of the sh l Pressure from water out beneath the fish Gravity b A sh oating in water is in hydrostatic equilibrium so forces balance in F h I Pressure from gases H d abo e the lab SINK MW 39 material 1 Equilibrium P sssss re from gases Weight of the slab below the slab a Material inside the sun is in hydrostatic equilibrium so forces balance Lec 5 Prof Sarah Higdon 24 12 Thermal Equilibrium Sun is hot and gaseous Gas more compressed at greater depth so Density amp temperature increases with depth Thermal Equilibrium Temperature at each depth approx constant Energy generated by fusion at core must be transported to the surface to maintain equilibrium eg too little and core temperature will rise too much and core will coo both bad news for us Lec 5 Prof Sarah Higdon 25 The Sun Is A controlled fusion reactor built in thermostat If the core temperature suddenly drops The Sun s pressure drops as the rate of fusion reactions decreases The Sun contracts As the Sun contracts it gets hotter again This increases the fusion reactions until pressure and gravity are in 39 balance again Hydrostatic Equilibrium gt ium Ium Lec 5 Prof Sarah Higdon 26 13 Energy Transport Given the basic properties of the Sun s composition Hydrostatic Equilibrium produces detailed temperature distribution within the Sun Photosphere Convection Temperature millions of K Distance from center km Journey of a Thermonudear Radiative Zone Core 07 Rsun enersycorc Radiative diffusion 39 Convective Zone T 2 x 106 K hydrogen recombination e hydrogen atoms ef cient absorbers of photons so medium becomes opaque Energy transport now via convection Conve ctive zone Slow progress radiative zone 696x105km takes 170000 Yrs 50cmhr Sungt Earth 150 million km takes 8 minutes Lec 5 Prof Sarah Higdon 28 Solar Model a My Center 01 39Jun Surface of Gun cult of Gun rm Sun39s rcn39cr mzrlar radii 0 r 04 06 08 10 0 Dimnm from Sun s time solar rad 08 10 is solar mini 01 4 lel niic from Su o h Center olSun outlaws wt Sun Center of Sun 3 of Sun Using the equations from hydrostatic and thermal equilibrium and energy transport we construct a scienti c model Core density 160000kgm3 14 x Lead Core Temperature 10 million K Core Pressure 34 x 1011 atm 1 atm in the class room Lec 5 Prof Sarah Higdon 29 Solar Interior Helioseismology 1960 Robert Leighton Caltech highprecision Radiativezone Convectivezone Doppler shift measurements of solar surface patches risefall 10 m every 5 mins Sun can oscillate in millions of ways Strongest tone 003hertz 13 octaves below our audible range Observations used to set limits on amount of He in the Sun and dEtermine the Computer simulation of sound wave thickness of the transition resonating in Sun red inward blue outward region between radiative and motion convective zones Lec 5 Prof Sarah Higdon 30 Solar Neutrinos direct evidence of fusion 1033 neutrinos per second leave the Sun 1012 pass through your head every second Hard to detect no charge and very low mass can pass through the Earth without interacting with matter but occasionally they do interact and can be detected Three types of neutrinos electron much and tau Sun only produces one type but the neutrinos can undergo an neutrino oscillation and change type before arriving at Earth Lec 5 Prof Sarah Higdon 31 The Sun is very Active We ve shown that the Sun s luminosity has been fairly constant over the last few billion years Now we will look at the outer layers ofthe Sun which are far from constant Lec 5 Prof Sarah Higdon 32 The Photosphere sphere of light Sun s visible light originates in this hot thin amp opaque layer of gas 400 km Temperature profile hot at bottom cooler at top Evidence Absorption lines Lower layer 5800 K cooler upper layer 4400 K Limb Darkening line of sight through limb only sees cooler dimmer upper layer Granules convection cells the size of Texas amp Oklahoma 1000 km again due to hotter lower layer An obsewcr team at the Sun s so v artwaymto the relatively cool photosphere rncc t is regmn appears era nge nd dtm What this observe Q 5655 What this v observer 5 An ohmm looking at the Top of photosphere To observe a m a V 0 appears yellow and bug L Lec 5 Prof Sarah Higdon Supergranules Lower contrast than granules hard to see Doppler Image shows supergranules giant convection cells 35000 km few hundred granules Churns at 04 kms 110 speed in granules lasts day Lec 5 Prof Sarah Higdon E Blue areas of Using gas Red areas of sinking gas 2quot t x t w 39 a life 3 gt huthwy I a team5133 1 ut ti551 538 l F3s if ft lt t 4quot r a quot if 11P 1 I V h iua lgtkl h h 39 i rquot 39 34 17 The Chromosphere sphere of color Spicules Normally invisible seen here during an eclipse which blocks the light from the photosphere The red gas is Halpha emission from the tenuous gas density is 10394 that of photosphere 10398 that of our atmosphere 2000 km thick and temperature RISES bottom is 4400 K top is 25000 K Note can see chromosphere at any time notjust eclipse if use a narrow Halpha filter Lec 5 Prof Sarah Higdon Cllronxlmpller 35 Spicules Jets of rising gas lasts 15mins rises few 103 km Spicules found above edges of Supergranules Spicules rising gas at supergranule boundary gas is cool and falling Not thermal motion gases pulled by Sun s magnetic field Lec 5 Prof Sarah Higdon Distance above top of photosphere km Corona Tmnsxuo n Chromosphete Interior 36 Solar Corona crown Hot thin gas 10396 x as bright as photosphere extends for few 106 km T 2 x 106 K see FeXIV emission line But compare densities corona 1011 atomsm3 photosphere 1023 Our atmosphere 1025 106 Energy density in photosphere much higher than in the Corona M Chromosphere J l 103 l I 103 104 105 Heght above photosphere km 4 Lec 5 Prof Sarah Higdon OI Solar Wind Corona s high temperature translates to high speeds 106 kmhr Some of the gas can escape the Sun s gravitational pull Composed mainly of electrons hydrogen and helium nuclei some heavier ions Winds stream out through coronal holesgas thinner Million tonnes 109 kg every second is lost as wind Is this a lot Given the Sun s mass 2 x 1030 kg And it will fuse hydrogen for 1010 yrs False color UV image What percentage of its mass will be lost as wind Lec 5 Prof Sarah Higdon 38 19 Aurora Electrons and ions from solar wind enter Earths Upper atmosphere spiral down magnetic field lines near poles Collisionally excite atoms in our atmosphere remember the photon firing range and the emission line spectra Lec 5 Prof Sarah Higdon Sunspots Lower temperature region in photosphere huge Earth and Jupiter sized spots Appear darker as lower flux StefanBoltzmann b Near sunspot maximum c Near sunspot minimum Flux from umbra 4300 K 5 03 Flux from photosphere 5800 K4 30 of the light compared to same size patch of photosphere Groups of spots like bar magnets leading group have SAME magnetic polarity to that of the nearest pole at Le N if closest to N pole following group have OPPOSITE magnetic polarity as nearest pole Lec 5 Prof Sarah Higdon 40 20 11 Year Sunspot Cycle Solar laltlude V 1380 1890 1900 1910 1910 1910 1940 1950 10 1970 19839 1990 1000 IOlO Date Butterfly diagram at begining of 11 year cycle spots found near latitudes 30 N amp 8 end of cycle nearer to equator Remember leading spots in a group have the same polarity N or S as the suns magnetic pole in that hemisphere Lec 5 Prof Sarah Higdon 41 Magnetic Dynamo model Afar 1 rotation Aft 2 rotations After 3 rotations many reunions Differential rotation measured by observing sun spots causes magnetic field lines to be wrapped and concentrated near equator Convection creates tangles amp kinks Sunspots appear where kinks protrude through surface of photosphere Differential rotation eventually undoes the kinks The leadingproceeding spots migrate to the equator polarity cancels as meets another proceeding group from the other hemisphere The following spots in the group migrate to the poles They have the opposite polarity of the pole and first cancel and eventually reverse the polarity Lec 5 Prof Sarah Higdon 42 21 Sunspots Produced by 22 Year Cycle in Sun s magnetic Field It is thought that the Sun s magnetic eld originates in thin layer between the convective and radiative zones The magnetic dynamo model successfully predicts Polarity of preceding and following spots preceding spots in a group have the same polarity N or S as the suns magnetic pole in that hemisphere Reversal of polarity of Sun s magnetic eld Formation of greater numbers of sunspots initially at high latitudes and at the end ofthe cycle in greater numbers closerto the equator Sun s magnetic poles reverse every 11 years so whole cycle repeats every 22 years Lec 5 Prof Sarah Higdon 43 Prominences Flares and Coronal Mass Ejections Promhlulces LeftHalpha image of chromosphere during sunspot maximum Bright plages beaches appearjust prior to new groups of sunspots Filaments appear dark cooler parts of chromosphere pulled upwards along magnetic field lines Seen side on they are called prominences can last for mere hours or months most energetic erupt as flares SOHO UV image Hell filter Lec 5 Prof Sarah Higdon 44 22 Solar Flares 1030 J 1014 one megaton nuclear weapons Brief eruption of hot ionized gas from a sunspot group Hazardous to astronauts and satellites Lec 5 Prof Sarah Higdon 45 Coronal Mass Ejection huge magnetic bubble of plasma e39ected from the Sun Coronal Mass Ejection is much 39 39 39 much larger than a solar flare rs 1012 kg a billion tonnes of high temperature coronal gas ejected into space at 100 s kms in the space of a few hrs Caused by magnetic reconnection See Fig 16 25b in book C l R P5 a A coronal mass ejection b Two to four dayslater Above SOHO X ray image of coronal mass ejection Sun s image is UV Takes a few days to reach Earth thank goodness for our magnetosphere Left TRACE falsecolor UV image 1 Showing glowing gas trapped along magnetic field lines Image of the Earth superimposed for smiel 46 23 Lecture 3 Previously in ASTR1020 I To study the universe we observe the electromagnetic radiation from stars gas dust galaxies comets planets etc Every object that has T gt 0K radiates and we try to observe it I Use physics to understand the physical mechanisms behind the observed radiation eg when objects collide their temperature increases I Electromagnetic Radiation I Charges set up E elds through all space I Disturbances ripples travel at c I Carry energy E hf E hcA I Electromagnetic Spectrum I Visible light 400700 mm only a tiny part radio 7 Gamna rays I Earth s atmosphere allows only some to reach surface I Blackbody Radiation Thermal Radiation I Smooth distribution of emission with or f I Depends only on T I Two simple Laws give temperature and total energy ux I Le 3 Prof Sarah Hidden 2 f Wien s Law There is a simple relationship between T and A of peak Wien s Law As T A peakquot As T me WM mu m 2 mm LE a PM Sarah H gdun a S t ephan s Law The Total Energy A Blackbody Radiates wquot quotru r5 Quadruple the temperature Flux Wm 9 44 4x4x4x4 256 times greater I Le a PM Sarah Hrgdun Lecture 3 r What is The Ring Nebula continuum emission arises from blackbodys eg stellar photospheres But we also see emission lines I Nitrogen red I Oxygen green I Helium blue IIIGIII LE 3 Pmr Saran ngdun 5 Today Spectroscopy Radiation amp Matter IIIDIII LE 3 Prof Sarah ngdun e Lecture 3 Reminder Free Physics and Astronomy Tutoring Room 2023 in MathPhysics Building I MonTuesWed 5pm7pm I Thur 6pm8pm IIIIJIII Lec 3 Prof Sarah Higdon 7 A Simple Spectrograph Spectrum sltt 650 nm White Light Y 500 nm II B KchmefYork J Gave Battle In Vain V 400 nm I White light is a mixture of all visible wavelengths I I I Q I I I Lec 3 Prof Sarah Higdon 8 Lecture 3 Blackbody radiation depends 600 nm only on Temperature 500 um I I 400 nm a I Sen ding Blackbody emission through a Spectrograph gives a continuous spectra I I I J I I I I Let 3 Prof Sarah Higdon 9 1 Hot gas in a glass tube aw 0 t Lec 3 Prof Sarah Higdon 10 Lecture 3 I I I Light comes out in a number of discrete wavelengths E 9 Emission Line Spectrum This pattern or spectrum is the same for any set onydrogen atoms I I I Q I I I I Le a PM Sarah ngdun M Each gas gives a distinct pattern of lines um I I l I MW 4 l M m 0 t t t I I I Lesa Pruf sarahmgdun 12 I I I I I I I I Lecture 3 Lecture 3 Absorption Line Spectra What happens to Blackbady radiation passing through coal gas 600 nm 500 nm 400 nm You get a continuous spectrum from the 6000 K Blackbody except that light is absent at discrete wavelengths The pattem of missing light depends on the gas between the source amp pn39sm As ifthe gas absorbed the missing light Le 3 WM Sarah ngdnn 13 The Sun s Spectrum Stacked salar 51mm 700400 nm A raz39nbowis a spectmm ofthe Sun 39 A closer look shows absorption lines my stmn lines ofiron calcium fairly weak lines ofhydrogen 9Earth is rich in iron and calcium little free hydrogen This sug ests composition Lagical hutwrang I mystery hnes present that couldn t be associated with any element on Ear 1 68 Given the 939 helium a er Gre name for Sun I 1295 Heliumamid on Earth It as the I most abnaaaat element a er Hydrogen l I Le 3 WM Sarah ngdnn M 39 ih made of Iron NO But there are trace amounts in it s atmosphere Ht t ll t t t n Illlmillllllllltllllllllllltlt Emissionspectrum ofiron I I I I I m the laboratory on Earth I II For each emission 1me of Iron there is a corresponding absorption Lec 3 Prof Sarah Higdon 15 Emissiori amp Absorption Line Spectra It was noticed in the laboratory that for any given gas the A of the absorption lines matched the A of the emission lines For example here s the emission top and absorption bottom line spectra of Calcium Lec 3 Prof Sarah Higdon 16 Lecture 3 Lecture 3 Kirchho s Laws The German physicist Kirchhoff summarized these observations I I I i I I I Let 3 Prof Sarah Higdon 17 I I I I I I I I I I El During this crisis physicists were determining basic structure of matter I I Let 3 Prof Sarah Higdon 18 I I I ll I I I I Lecture 3 Rutherford s Experiment 1910 Itwas like firing a 15 inch shell at a piece of tissue paper and it came back and hit youquot Radioactive substarice 39 Most alpha particles emits a1pha parades I pass throught e oi 1 With Very little de ection V Direct evidence 1 1 ofa massive 39 amp compact 7 atomic nucleu r39 x B Gold ci1 1 seen edgecri Occas onally ari a1pha partic1e rebounds like A or B1nd1cat1ng that it has collided With the massive nucleus of a go d atom Lees F39er Sarah ngdun 19 I Q I I Rutherford s Atomic model All matter composed ofatoms All atoms composed of3kinds ofpanicles prawns heavy17x10 g c arge neutrons heavy17x1077kg neutral 1e 0 charge electrons light 91x1031 kg charge MpMe 2000 Mostly empty space nucleus 1O3914 m atom 103910 m imagine a bean on the 50 yard line I I I I I I at the Rose Bowl Stadium I I Le 3 F39er Sarah Higdun 2E1 More Correct Picture of an Atom m chm up mmwhdsww umm My mm Akmd V m If 5 IQ u m c cum quoton mavon m mam mu m xcnm an n L253 Prur Sarahngd n IIIQIIII I I I I I I I I Atomic Structure I Helium 271 7er 2e h n H m a 751 SN 6e 3 I e j a g E l wnwnwrmu In a 1 mr u a a Nutmxcam IIIEIII Lecture 3 Lecture 3 Atomlc Structure II Energy Diagram for Hydragequot 5 4w excitcd 4 3quotI excitcd 121 cV 3 2nd cxcitcd 102 6V 112 15 excitcd m I I I I o n1 Ground I I I Let 3 Prof Sarah Higdon 23 39 J 134 3 Ionization 5 4111 391 d 127 eV Lg E3quot ii tid 121 eV 113 2 cxcited a 102 2 1st excitcd is H I I i I Exam 2 g 0 cv 7 n71 Ground I Let 3 Prof Sarah Higdon 24 q Absorption of a Photon by Hydrogen Input photons lllll Lec 3 Prof Sarah Higdon 136 127 eV 121 eV 102 eV 115 439 excited 114 3quotI excited 113 2quot excited 112 15 excited 111 Ground Output photons llll IIIHIII IIIIJIII Emission of Photons after Absorption MW 127 31 121eV 102 eV 1 115 439 excited j39 quot1 mm 113 2mI excited 4 1st excited 111 Ground Lec 3 Prof Sarah Higdon IIIZIIII I I I 394 I I I I Lecture 3 Lecture 3 Incident photons IIIIJIII Lec 3 Prof Sarah Higdon 27 Ionization of Hydrogen Atom 136eV Ian atian 5 4 excited 127 eV 4 3m excited 121 W7 3 2mI excited 102 Ni 71 1 excited I I Photon with E gt 136 eV a 0 39 El I 0 eV 7 n71 Ground Let 3 Prof Sarah Higdon 28 a T rangitions in Hydrogen Atom Lec 3 Prof Sarah H gdon 29 K irchhoff s Laws Revisited Hm blmkbod g dark line nspmmnn nu usspt rum r 39slighnn I y med um mm m same wmlmums at which my ah vrbrd in I I I I I I I Lec 3 Prof Sarah H gdon 30 Lecture 3 Photon Firing Range 1 jun man 7 31mm mun U mm W73 I 39l I I I I u I W WW5 IIIIII Galaxy Spectra Galspec on my laptop or see web link httQIl39wwwastrowashington eduIabsh ubblelawspectrahtml I I I I I I I IIIIIIII LE a PM Sarah ngdun 32 Lecture 3 Lecture 3 39 Molecules are more complicated than single atoms P and so have much more complicated energy levels 15 llquot I 39 Molecules can do something atoms cannot do I otate amp ibra e I 39 Rotational amp Vibrational energies are quantized quotJ molecules rotatevibrate at discrete ire uen Rotation amp Vibrational transitions give lines in IR I I IIIQIII Lec 3 F39er Sarah ngdon 33 Transitions in simple molecules M m whrzmon h i v Fast2 yunanon 9 my ma Lena w Sarah ngdun 34 mow mam Lecture 3 Polycyclic Aromatic Hydrocarbons PAH Very Important Astronomically Found in many objects Comets to Starburst Galaxies 15 ofinterstellar carbon Polycyclic Carbon Rings Note Benzene has only 1 ring so not really polycyclic Aromatic really Hydrocarbon made of Hydrogen and Carbon Lec 3 Prof Sarah Higdon 35 Snake biting its tail The electrons float above and below the ring and the electromagnetic fields they generate keep the ring flat 06W IIIIIIIII Lec 3 Prof Sarah Higdon 36 Polycyclic Aromatic Hydrocarbons Napthalene Chrysene C10H8 C18H12 Pyrene Coronene Ovalene C16H1o C24H12 032H14 I I I it I I I I IIIQIII LE 3 WM Sarah ngdan 37 PolyCyclic Aromatic Hydrocarbons Complex molecules in the Infrared 1 gm 5 e m 12 Wave e m pm IIIt IIIEIII r44 warm um Lecture 3 Lecture 4 Previoust in ASTR1020 A prism is a simple spectrograph sons incomingEM radiation by A or v 3 kinds of spectra continuous spectm absorp on line spectra amp emission line spectra Kircho Laws ahot dense gas or solid emits acontinuous spectrum ruiaenbody 39 39 39 t39 quot 39 a cool gas m r lines Atom tiny nucleus protons amp neutrons plus a cloud of electrons Atomic energy levels are quantized An electron can only occupy discrete energy levels t i i t t a phown E i t tn opp ii iorifitis sufflclent Lo lonlze the atom l e the electron leaves the atom 39 u The electron can only emit a photon IF the energy othe photon aiactly matches Hi l andLhel ll luldtul electron moves to I Each atomic species egHHe cFe si has its own energy level diagraul I Molecules are bound groups of atoms coz H20 They can rotate amp vibrate similar rules for absorptionemission ofEM radiation apply I i n carbon LEEA Pruf Sarahngdun 2 I Lecture 1 39 Overview 1t Lecture 4 Lecture 1 39 Overview I Emission of Light after Absorption n5 am excited n 3d excited 1 2quot n3 2quot excited 1n 2v an mini quot 2quot Gmum l aim1m a M u llll lll 1 Photon Flrlng Range For a fun tutorial to help you learn about the Hydrogen atom go to 1 z 32 L 2 E lquot 391 1 2 L I quotM J L Lab rm mamww 1 Lecture 4 Lecture 1 Overview Molecular spectra more complex than atomic spectra I Electron transitionsvisible amp ultraviolet lines I Vibrational transitions infrared lines I Rotational transitions radiowave lines a molecular hydrogen b atomic hydrogen Illauni L254 Prur Sarahngdun 5 WaveParticle Duality of Light We have been thinking of light as a kind of wave Also light behaves like bunches of particles eg Kirchoffs Laws I I I I I I I I L254 Prur Sarah ngdun 6 1 Lecture 4 Lecture 1 Overview InClass Quiz 2 I Use your text book and talk over your answers with your neighbor L254 Pmr Sarahngdun 7 Todayisjlectu re Telescopes 1 Lecture 4 Lecture 1 Overview Telescopes JEHJN H V quotox lbwquot ml quot110 L854 F er Sarah H gdnn 9 T Astronomical Detectors The rst astronomical detector was the human eye M 33 drawmg by LordRosse L854 F er Sarah H gdnn 10 1lt Lecture 4 I Astronomical Detectors Modem image ofM 51 Lord Rosse 5 Sketch of M 5 1 L254 Prur Sarahngdun M Limitations of the Human eye vi 1 amm l i L254 Prur SarahH gdun 12 Lecture 1 39 Overview 1 Lecture 4 L254 Pmr Samh Htguun 13 Refraction Refraction is the bending of light as it passes from one medium air into another glass tmw I Keypoint ltght travels slightly slower in glass than it does in the air mmtgmmmm L254 Pmr Sarah Htguun M Lecture 1 Overview 1 Lecture 4 Bringing Light to a Focus Rtlnmml ernlnon L254 Prur Sarahngdun 15 Refracting Telescopes Lenses Re actjng telescopes have a large lens called the nbjet ve at one enol It serves to collect light from stats galaxies etc and hnng that light to one pointr the tux or focal point lacommo hgh lays Focal cnqlh The Fucal Ungth is just the distance from the lens to the fncux L254 Prur Sarahngdun ls Lecture 1 39 Overview 1 Lemma 4 The World is upside down AnuLha39lens called Lhaeyepieaz xsusedtu ma wthe suurce bmugm the0cm mu m m mmquot Problem Chromatic Aberration mu m m mmquot Lemma 7 Ovenyew 774m Lecture 4 Problem Chromatic Aberration Suns fncusad m ml light 39 havehluz amp gum halns L254 Prur Sarahngdun 19 L254 Prur SarahH gdun 2n Lecture 1 39 Overview 1 Lecture 4 F T ypes of Telescopes Re ectors Re ecting telescopes use a curved mirror to collect light from an object and bring it to a focus where it can be analyzed An image of the object is formed at the prime focus 9 Note that it is turned upsidedown Lec 4 Prof Sarah Higdon 21 Incoming light rays Mirror axis Focal length Lec 4 Prof Sarah Higdon 22 The primary mirror is typically made of a special glass that doesn t expand or contract as temperature changes The curved side is coated with a thin layer of aluminum that is highly re ective Lecture 1 Overview 1 Lecture 4 All Modern Optical Telescopes are Re ectors Advantages 3f Re ectors Much Greater Light Gathering Power Lenses can only be supported by the sides A big lens will sag in the middle under its own w 9 This reduces the ability to focus light amp distorts im 9 Practical limit on the size oflens to N 1 meter ght ages N rrors can be supported on their sides amp bottom a Very large mirrors can be built and supported L254 Prur Sarahngdun 24 Lecture 1 39 Overview 1 Lecture 4 Lecture 1 OveM39ew L224 Pm Savah Higdun Big Mrrars Anotha approach 15 to build up big mirrors out of many smaller mirrors These are called Szgmzntzzl Mirmrs and are used by the Keck helescope Nu real limit in the size at telescupe mirmrs NOAO39SVEry Large Talescuper rm m meme am L224 Pvu18avahHigdun 14 Lecture 4 I Advantages of Re ectors Compact Designs Since they can be easily supported mirrors with deep bowls can be polished resulting in short focal lengths Much more compact re ectors can be built 9 Save money on telescope building a big chunk of change Ham 6quot mm mun refmcmr largesthuilt L254 Pmr Sarahnguun 27 Advantages of Re ectors Simplicity Alens must be accurately shaped amp polished on both sides Il it is a Compound Objective lens on at least four sides 9 This takes time and money to do correctly Mirrors only have to be shaped amp polished on one side 9 Easier and cheaper to fabricate a big mirror L254 Pmr Sarahngdun 28 Lecture 1 39 Overview 1 Lecture 4 LEE 6 PM SavahHludun 9 Advantages of Re ectors No Chromatic Aberration To Correct A lens sends red light and blue light tn 2 different l39ucus Objects stars have colored halos around them gt Can be corrected but 15 aipmslve at complicated Mimirs bring all culnrs tn the same l39ucus No colored halos IDIJI I III39JIIII Cannot be c LEE 6 PM SavahHludun 3 Advantages of Re ectors No Light Losses In a Rmzaing telescupe light has tn pass Lhmugh the lenss The Glass W111 absorb light especially at infrared ths and ultmmlet wavelen meted or adjusted casting reflect UV thnmgi IR ligIt wiLh Mirror essentially 100 39 ciency gt Some re ective coatings are better in the UV silver me are better In the IR go gt Aluminum has the best Wlde spectrum re ectivity I I 394 I I I Lectule7 Ovevew 774w Lecture 4 Lecture 1 Overview 7 There are many types of Re ecting Telescopes anr rim Summary mmquot t 7 o 39 u n u 131va m mus Lec 4 Prof Sarah Higdon 31 a Al Schmidt Telescope Mirrors amp Lens T39sl rr39w Schmidt telescopes allow photographs to be made over very wide elds of view with no distortion Curved imaging surface Designed for surveys ofthe sky In 1948 Palomar Observatory with the National Geographic Society started a photographic atlas of the Northern sky 936 photographic plates each 6 wide 12x the moon s diameter were exposed 98million objects detected and cataloged U I I 15 I Lec 4 Prof Sarah Higdon 32 Q 1 Lecture 4 Lecture 1 Overview Survey extended to Southern hemisphere UK Schmidt Telescope A random example This is third cluster found by Shapley in Centaurus1936 Pederson et al 1978 optical knots extragalactic Hll regions Longmore et al 1979 deep Schmidt plates approximating B and U bands found 24 Knots dwarf galaxies Lec 4 Prof Sarah Higdon 33 Lec 4 Prof Sarah Higdon 34 1 Lecture 4 I Angular Resolution of a Telescope In Theory mm m L254 Prur Sarahngdun Lecture 1 39 Overview a Angular Resolution Glian u AR6 n AR5n AR11 Andromeda Galaxy 25 million lightyearsdistant L254 Pruf sarahHgdun 1 Lecture 4 L254 Prur Sarahngdun n name my Angular Resolution of a Telescope In Practice In reality turbulence in the Earth s atmosphere limits the smallest detailwe can see in objects to AR 1arcsecond L254 Pmr Sarathgdun fr tm g39For The Earth s Atmosphere Adaptive Optics With A Laser Guide Star Telescope shunts a laser ham tuned m an arti cial guide 5131 Small exible minur is adjusted un st timescalesll umesa secund to current atrnusphenc distumuns un guide star de zras small gm 5 E39 tar a u may greatly lmpmve the angular resulutmn Stamveommal 39anueat manumvrmsasss m A hummus Newmch Lecture 1 39 Overview 1 Lecture 4 Adaptive Optics Dealing with the Earth s Atmosphere m 1 a We 0 quotJam Adaptive 0pm mrnedan L254 Pruf Sarah mgan 39 I I I tvnnkle39 umescalg GreatestProgress has been made m ths wavelength band I age on le shows agood opaea1 image lt1quot ofa star cluster NGC 6934 Image on ngm I a a a 1 I I I I I I I I L254 Pruf Sarah mgan 4n Lecture 1 Overview 1 Lecture 4 Avoiding The Earth s Atmosphere Space Go above the Earth s atmosphere altogether HST L254 Pruf Sarahngdun M IIIrole Making an Image Photographic Plates p cially polished glass plates coated with photographic emulsion Advantage over eye 1 can photograph my wide eldx nfvim up to several degrees acrossl 2 can integrate or collect photons to build up an image L rl r l rmmute ex usure L254 Pruf Sarahngan Lecture 1 39 Overview 1
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