Intro To Stars And Galaxies
Intro To Stars And Galaxies PHYS 1060
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Date Created: 09/30/15
Tuesday 23 September 2008 PHYS 1060 1 Fall 2008 330 445pm Tu Th 1 104 Rood Dr Philip Edward Kaldon Western Michigan University Unit 1 Powers of 10 magnitudes 1 ME You The Sun 10 planets in our solar system 100 years of life 1000 miles to New York or Florida years of Civilization 10000 kilometers size of Earth 100000 miles to the Moon 1000000 10000000 100000000 population of US miles to Sun 1000000000 pop of world 10000000000 years ever 100000000000 stars in Milky Way Speed of Light 186000 miles per second 300000000 meters per second corrected number 7 there was a typo The Astronomical Unit The distance from the Earth to the Sun 93000000 miles 150000000 km or 150000000000 meters Constellations and Asterisms 88 recognized Constellations as seen from the Earth Angular Size The circle is divided into 360 Each 1 is divided into 60 minutes Each 1 is divided into 60 seconds 3600 1 and 1296000 360 Same Angle Hipparchus c190 120 130 First Magnitude the brightest stars Sixth Magnitude the faintest stars we can see Apparent Magnitude Seen From Earth Absolute Magnitude From Standard Distance 10 parsecs 326 LY Apparent Magnitude is based on our observations Brighter lower number means Closer and or More Powerful in Actuality Magnitude is a Logarithmic Scale A Simple Log Scale Might Be Powers of 10 091 1910 29100 391000 15 a 1000000000000000 mB mA 2510g1AIB 1A NB 2 2512m3m mB mA difference gtltbright 6 6 0 same 1 6 5 1 2512 6 4 2 6310 6 3 3 1585 6 2 4 3982 6 1 5 1000 6 525 075 200 6 450 150 400 Eclipses Some Models of the Solar System Universe Sun 93 000 030 miles away Earthcentric Model with Mercury amp Venus locked with Sun Seasons 01 a e c g b Heliocentric Suncentered Model with epicycles 2312 angle of inclination Kepler s Model with exaggerated ellipses Kepler s Laws 1st Law Planetary orbits about the Sun are ellipses and the Sun lies at one of the foci of the ellipse 211d Law A line connecting the Sun and planet sweeps out equal areas in equal times 3 1 Law p2years a3AU p period time to go around once a semi major axis half of the long side of an ellipse An Ellipse The Eccentricity of an ellipse tells you how stretched out it is A circle is a special case of an ellipse With an eccentricity 1 Planetary orbits turn out to be pretty close to circular but just elliptical enough to matter Because orbits are Elliptical there are two important points in an orbit apogee and perigee apogee ap ej noun 1 a The point in the orbit of the moon or of an artificial satellite most distant from the center of the earth b The point in an orbit most distant from the body being orbited French apogee from New Latin apogaeum from Greek apogaion from neuter of apogaios far from the earth apo apo gaia earth ap39oge an je en adjective perigee p r eje noun 1 The point nearest the earth39s center in the orbit of the moon or a satellite 2 The point in any orbit nearest to the body being orbited French perigee from Medieval Latin perige39um from Late Greek perigeion Greek perL peri Greek ge earth per39ige39al j el or per39ige an je en adjective About the Sun aphelion and perihelion a phe H on ere39ieen erei39yen noon piuraa phe li a ties The point on the orbit or a celestial body that is farthest from the sun From New Latin apneiiorn Greek eon aoo Greek news sun per i he H on p r eeh i en hei39yen noun piuraiperi hell ahe39ieehei39 e The point nearest the sun in the orbit or a oianet or other celestial body Aiteration ofNeW Latin perineiiom pen Greek tieins sun per39i he li al he39ieeihei39yei adjective Motion Position where you are Speed a change in position Direction where you are heading Acceleration a change in speed and or direction Mass how much stuff you are Weight mass under gravity Momentum mass times speed The only way to change your momentum is to use a Force Newton s Laws The Zeroeth Law There is such a thing as mass The First Law An object in motion tends to stay in motion or an object at rest tends to stay at rest unless acted upon by a net external force The Second Law F m a Force mass gtlt acceleration The Third Law For every action force there is an equal and opposite action acting on the other object A pushes on B so B pushes on A How Do We Know It Is So Observation Hypothesis Theory Testing Re nement Most people don t use the word theory to mean what it means in science As a result many arguments about theories don t make any scientific sense Forces Contact Forces Action at a Distance Gravity Newton s Law of Universal Gravity FG GigiI2 G universal constant M1 and M2 are masses of 2 objects r distance between their centers Inverse Square law 1 r2 Yet Again Double the distance 14th the force Double one mass twice the force Falling Near The Earth f Falling Around The Earth or Sun Orbits v In Either Case if v 0 Then Falls Straight Towards Earth or Sun Kepler was right Elliptical Orbits for Bound orbits Newton showed that there were two kinds of Unbound orbits parabolic and hyperbolic Grazing orbits which pass by and never come back hyperbollc paiapolic elllptlcal Energy Kinetic Energy motion Potential Energy stored Radiative Energy light Orbital Energy KE PE Conservation Laws momentum energy Angular Momentum m X V X r Ice Skating spinning Conservation of angular momentum Gravitational Encounters 0 Change orbits o Slingshot effect Escape Velocity the speed at which gravity cannot bring you back For Earth 1 1000 ms or 25000 mph Voyager 2 Probe has reached solar escape velocity it is leaving the solar system and is not coming back Chapter 5 on Light We ve discussed some parts of Chapter 5 but will pick it up again after Exam 1 and then go into Unit 2 Thursday 30 October 2008 PHYS 1060 1 Fall 2008 330 445pm Tu Th 1 104 Rood Dr Philip Edward Kaldon Western Michigan University Unit 2 The E M Spectrum con t The Nature of Light Wave Particle Duality Light as a Particle photon E h f h Planck s Constant 663 X 103934 J39s Light as a Wave c f 7 f frequency Hz 1 sec 7 wavelength meters c speed of light 300000000 ms in vacuum light is slower in other materials Matter Matter and Light 0 emission 0 absorption o o protons charge 0 neutrons neutral 0 electrons charge Classic Electrons Whirling Around Nucleus J Bohr Hydrogen Atom Ground State Energy Released as Light E t d qt t N M Add 39 When Dro in to a Lower m e 3 93 ee 0 8126 Of a Hydrogen atom Level pp 9 Energy to Ground State 1X10391Om 1 l0000000000 rn size of the nucleus 1 100000th of an atom a transmission goes through 0 re ection 85 scattering bounces o Stefan Boltzman law more photons of all wavelengths than lower T and new photons at higher energiesshorter wavelengths than from lower o Wein s law higher T means higher average energy shorter wavelengths Spectra 0 continuous 0 emission 0 absorption like fingerprints combine with Doppler shift Temperature Scales 212 100 373 1142 vl39wata39 986 37 310 Human mrmal as 20 293 Room Temp 32 o 273 MP or ice 40 40 233 only 400 r110 779 194 dry ice 7321 7196 77 liq ninogen 460 7273 o Absnlme Zem Black Body Radiation objects radiate light 81 energy based on their temperature For Sun T 5777 K blackbody Main Sequence Stars Exam 1 Scores X1rraw 30 X1raw 150 X1curved 150 O B A F G K M X1rraw X1raw X1curved 17 85 104 16 so 100 Oh Be A Flne Guy chk Me 29 145 150 15 75 96 27 135 144 14 7o 92 26 130 140 12 60 86 Our Sun IS a G type star 25 125 136 11 55 82 24 120 132 9 45 76 actually a G2 star 23 115 128 22 110 124 n 110 110 110 median 21 105 120 hi 29 145 150 mean 20 100 116 lo 9 45 76 19 95 112 ave 2054 1027 1182 18 90 108 sd 4105 2052 1611 Little tiny red dwarfs are M types To get Percent Grade find X1curved 15 So O types must be really large and hot A Minor Issue in Quiz 5 a Brightness Amount of Light Intensity LightArea Luminosity the rate at which energy of all types is radiated by a star in all directions A star s luminosity varies approximately as the square of its radius and the fourth power of its absolute surface temperature I probably should ve labeled the graphs Brightness not Intensity More De nitions Atom a neutral object with equal numbers of electrons and protons Ion a charged atomic system with either extra electrons negative ion or missing electrons positive ion Element atoms with the same number of protons Z atomic number Isotope same element but different number of neutrons N atomic mass A Z N Hydrogen a Unique Case of Isotopes H Z 1 NO regular old hydrogen doesn t need a neutron to stabilize the nucleus The most common material in the universe D Z 1 N 1 heavy hydrogen has one neutron also called deuterium Stable but uncommon Twice the mass of regular hydrogen but still has same chemistry Heavy water is D20 not H20 T Z 1 N2 super heavy hydrogen has two neutrons also called tritium Radioactive so it will eventually decay into another element Also behaves like H in chemistry Telescopes More aspects of angular resolution 1 Light Gathering Area Telescope size generally given in diameter D 2 Angular Resolution Remember the 3rd Dimension 39milar angular size could be larger star further away The Sun The Earth R 695000 km RE 6378 km M 330000 ME ME 594x1024 kg 98 H and He z5940000000000000000900000kg 1 1 year Sunspot Cycle The Butter y Pattern 1645 1715 The Maunder Minimum The Little Ice Age Chapter 1 1 1 Apparent Brightness vs Stellar Luminosity Luminosity Power Output Power Energy Time Watts 100 W 100 Jsec Apparent Brightness Luminosity 47 cl2 Double the distance the area of the spherical shell of expanding light is 4 times as big so the apparent brightness is A Luminosities of the stars seems to range from 10394 Lsun to 105 Lsun or about 00001 ofthe Sun s Luminosity to 1 000000 times the Sun s Luminosity Table 111 p 306 Hertzsprunge Russ e11 diagram Moving Exam 2 from Tuesday to Thursday 30 October 2008 Things We Can Learn From The HeR Diagram Main Sequence Distribution an Those bands NOT Main Sequence The H R Diagram plots Luminosity vs Temperature Color But we can also see patterns in 0 Size Solar radii 0 Mass Solar masses 0 Lifetimes Millions or Billions of Year The Most Luminous Stars in the Main Sequence are also the largest and have the most mass but also the shortest lifetime Their mass means more gravity to compress them which means higher temperatures which means ultimately they burn their fuel faster All of the properties we see on the H R Diagram can be boiled down to MASS Our Sun is Spectral Type G2 Luminosity Class V G2 LC V Giantsa Sugerg ants and White Dwarfs Giants Aldebaran K5 III 350 Lsun 30 Rsun not nearly as large as even the orbit of Mercury Supergiants M2 1 38000 Lsun 500 Rsun past the orbit of Mars Mercury Venus Earth and Mars would all be inside this star Since these giants and supergiants are NOT hot but very luminous their brightness comes from SIZE large surface area Old stars Stars which used to be on the Main Sequence and have gotten old Mid life crisis Really really big ones deviant stars White Dwarfs are essentially the exposed cores of stars The Old Retirement Home Star Clusters Open and Closed Globular Clusters Star clusters are Localized The stars are all about the same distance from Earth and all about the same age Open clusters in the at plane of the galaxy Where the dust and gasses are Globular clusters are in the halo or sphere around the galaxy and are very old Stellar nurseries Age of Star Clusters Chapter 5 on Light We ve discussed some parts of Chapter 5 but will pick it up again after Exam 1 and then go into Unit 2 Thursday 20 November 2008 con39ected PHYS 1060 1 Fall 2008 330 445pm Tu Th 1 104 Rood Dr Philip Edward Kaldon Western Michigan University Unit 3 median mean Exam 2 Scores X2rraw 30 X2raw 150 X2curved 150 X2rraw X2 raw X2curved 15 75 14 70 13 65 27 135 150 12 60 26 130 147 11 55 25 125 142 10 50 24 120 137 8 40 23 115 132 22 110 127 21 105 122 n 110 110 20 100 117 hi 27 135 19 95 112 lo 8 40 ave 1888 9441 18 90 107 sd 4105 2052 17 85 102 16 80 97 To get Percent Grade find X2curved 15 110 150 1114 2042 Things We Can Learn From The HeR Diagram Our Sun is Spectral Type G2 Main Sequence Distribution Luminosity Class V an Those bands NOT Main Sequence G2 V quot 1 Solar Radius Star Clusters Open and Closed Globular Clusters Star clusters are Localized The stars are all about the same distance from Earth and all about the same age Open clusters in the at plane of the galaxy where the dust and gasses are Up to a few thousand stars loosely held together by gravity Globular clusters are in the halo or sphere around the galaxy and are very old Up to a hundred thousand stars tightly bound by gravity No dust or gas Low metal stars Stellar nurseries The HiR Diagram for an Open Cluster is cut off at the high mass end 0 B A and though it has a strong Main Sequence line there is some spread outward Age of Star Clusters The Main Sequence Turnioff occurs because the stars in a cluster are roughly of the same age m the high mass stars have shorter lifetimes So as the star cluster ages a 39 ss stars will end their hydrogen burning life and leave the Main Sequence HiR Diagram for two clusters M67 and NGC 188 Recall that the Main Sequence stars have age estimates based on their mass So NGC 188 is older than M67 Stellar Lives Cloud 7 Protostar 7 collapsed down to a spinning object but not enough yet for thermonuclear ignition in the core When the core reaches 10000000K 7 hydrogen fusion g f cient enough for the star to ignite Stabilization takes time 0 star maybe 1000000 yeaIs G2 star maybe 30000000 years Perhaps not so strange when you consider that for our G2 star it takes several million years for light to get out to the surface from the core Main Sequence high end about 150 solar masses but this number is nder debate low end for mass 008 solar masses or about 80 Jupiters The Sun s Life Life cycle of the Sun M Grams Walmmq 0 mm W 12 13 u 1 u thonsal mus laupmx Hydrogen ignition 7 10000000 K Helium ignition 7 100000000 K uires 05 solar masses and u requires mass pressure gravity to reach that temp What is so surprising about stars is the link between these large objects and quantum mechanics 7 the study of the very smallest of things inside the atom AN IMPORTANT NOTE The current Quiz 7 mismarked as Quiz 6 in some handouts is about drawing an H7R diagram The scale of absolute magnitudes SHOULD go from 20 at the bottom to 75 at the top because we want the most luminous stars at the top The scale says 5 to 720 which es no sense I really wish someone who had noticed this had sent me an email alerting me to the error A corrected handout can be downloaded at the website if you wish l 7 condensing phase 2 7 protostar 3 7 Main Sequence 4 7 Red Giant 5 7 White Dwarf Because of this confusion we will extend the Q7 deadline to Tuesday 18 November 2008 A Comparison of Main Sequence Stars color and size Note the puny little yellow G star towards the left There is tremendous variety in star classifications because each star has its own composition and age A young G star is different than an older G star ome stars are Variable stars Giant stars build up carbon and other elements Wolf Rayet stars W or WR Helium rich or are they late stage supergiants which have blown away their hydrogen shell exposing their helium cores Br wn dwarfs L 1300 2000 K T 700 1300K Y lt 700K Fig 12717 Number ufnucleons m nucleus Mass per nucleon The Iron Minimum Isotopes on the left can use fusion to reach honess and release energy Isotopes on the right can use ssion to reach honess aha release energy During the death ofa massive star the energy of the collapse can drive the fusion reactions past Iron756 but cannot sustain the energy Fig 12718 COSMIC ABUNDANCES of the elements 01 7 H9 001 rare earth elements oddyeven effect l LNWWJ 000000000001 e Be l l l l l l l l l 10 20 30 40 50 60 7O 80 90 atomic number Z For every 1 Hydrogen atom there is a tenth ofa Helium Other elements are even more rare This is a log plot 7 the vertical axis is not evenly spaced but each division is 10 times smaller going down Note that Carbon is MUCH more plentiful than Beryllium Be is made from 2 He while C is made from 3 He Shells of Fusion Layers Prior to Stellar Collapse of Large Stars M gt 8 MSun Why Iron Fe at the center Mass to Energy Conversion E mc2 411H gt24He 2 neutrinos energy If core T exceeds 10000000 K 107 K 4 Hydrogen nuclei fuse into 1 Helium nucleus energy gamma rays 2 neutrinos at a rate suf cient to balance off the loss of energy in the form of light at the star s surface ie it s luminosity In our Sun the central temperature is at present about 157 million K and 6138 million metric tons ofH are fused into 6095 million metric tons of He each second By the way What happens to the other 43 million tons of matter processed per second The Pressure Gravity Balance in Larger Stars Higher Core Temperatures Larger Size and More Mass But Lower Density mass to Volume ratio If all Main Sequence stars had the same density then R M1 3 But it is more like R M06 And the Luminosity goes as L R2 T4surface So the larger hotter stars are also more luminous To be more luminous requires more fusion at the core burning through the hydrogen fuel at a much faster rate Figure 1222 Protostar 25 Msun Blue Main Sequence star CNO cycle Red Supergiant Helium burning Supergiant core expands hydrogen burning shell shrinks Multiple Burning Supergiant Supernova Neutron Star or Black Hole Protostar 1 Msun Yellow Main Sequence star proton proton chain Red Giant hydrogen burning around inert helium core Helium burning star Double shell burning inert carbon core Planetary Nebula White Dwarf Fun with Fusion Z of protons N of neutrons A ZN of nucleons neutrons amp protons If we fuse two nuclei together our nuclear reaction looks something like XZY Energy Etc 12 Carbon l2 6C has 6 protons and 6 neutrons and a mass of 12000 amu But each proton by itself has a mass of 1007825 arnu and each neutron has a mass of 1008665 amu So is the Whole greater than the sum of its parts Well as you can see 6 p s and 6 n s have more mass than that of the Carbon 12 nucleus Since you can tjust hide mass forming the Carbon l2 nucleus must have some freed that excess mass as the binding energy for the nucleus or the energy that holds it together 6 protons gtlt 1007825 amuproton 6046950 amu 6 neutrons gtlt 1008665 amuneutron 6051990 amu Total mass of6 p 6 n 12098940 amu Carbon12 made of6 p and 6 n 12000000 amu Excess mass of pieces 0098940 amu Nova and Supernova A Nova is a potentially recurring explosion in a star typically caused when hydrogen from a companion star is pulled into the strong gravity of a white dwarf and ignites Supernovas are massive explosions as when a large mass supergiant reaches the iron minimum and is unable to continue multiple shell burning in the usual way or when hydrogen from a companion star falls into a white dwarf and suf ciently raises the temperature for the inert carbon core of the white dwarf to suddenly begin fusion Neutron Star Degenerate matter remnant from a supernova explosion of a supergiant star The gravitational force is suf ciently large to crush the neutrons protons and electrons of the atoms into a large 39 block of neutrons neutronium Black Hole Supernova remnant with enough gravity to prevent light from escaping Hence it looks black like a hole in space
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