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General Astronomy Stars and Galaxies

by: Stephan Kuvalis

General Astronomy Stars and Galaxies ASTR 1120

Marketplace > University of Colorado at Boulder > Astronomy > ASTR 1120 > General Astronomy Stars and Galaxies
Stephan Kuvalis

GPA 3.89


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Class Notes
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This 11 page Class Notes was uploaded by Stephan Kuvalis on Thursday October 29, 2015. The Class Notes belongs to ASTR 1120 at University of Colorado at Boulder taught by Staff in Fall. Since its upload, it has received 24 views. For similar materials see /class/231961/astr-1120-university-of-colorado-at-boulder in Astronomy at University of Colorado at Boulder.


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Date Created: 10/29/15
ASTR 7120 General Astronomy 391 5 Tars amp Galaxies axMWMfmm Midterm 3 next Thursday 0424 covering lect 1521 and corresponding reading in Ch 1922 last part of class today will be review next review with Abhishek tomorrow Wed 0423 6730pm Duane G125 HW 9 last and very short due Fri 0425 by 5pm ALTERNATE FINAL on Friday May 2nd 1000am 1230pm in the JILA auditorium Lessons from Imaginary Universes Cold Slow dark matter works better than hot fast dark matter Neutrinos are too fast structure would be smeared out What is slow and dark enough We don t know yet Particle experiments under way T39 RVIEW Ybillion lighbyears 5 c 39 i 35 million lightyears 39 9 1 og nnon lightwears 500 milliinightyears 1 Numerical simulations of structure formation Clicker Question What do we mean by largescale structures Massive central dominant elliptical galaxies Massive spiral galaxies with star birth rates more than 100x that in the Milky Way Supermassive black holes that reside at the centers of galaxies Huge walls of galaxies and clusters of galaxies The giant architectural monstrosity that is the engineering building on CU s campus Clicker Question What do we mean by largescale structures A Massive central dominant elliptical galaxies B Massive spiral galaxies with star birth rates more than 100x that in the Milky Way C Supermassive black holes that reside at the centers of galaxies D Huge walls of galaxies and clusters of galaxies E The giant architectural monstrosity that is the engineering building on CU s campus Some say the world will end in re Some say with ice From what I ve tasted of desire I hold with those who favor re But if I had to perish twice I think I know enough of hate To say that for destruction ice Is also great And would suf ce Robert Frost 18741963 Dark Matter and the Fate of the Universe Expansion begins with the Big Bang we ll talk about this next Tuesday At that point everything in the universe is flung apart at outrageous speeds Several different models for Past and Future depending upon the amount of dark matter Predictions of General Relativity Theory GTRl Einstein in 1917 realized GTR predicted universes in motion but preferred steady state added cosmological constant CC as repulsive force in spacetime to counteract attractive force of gravity A fudge factor Willem de Sitter A Dutch 1917 solves GTR equations with no CC and low density of matter showed universe must expand Alexander Friedmann M Russian 1920 solves GTR with no CC but any density of matter universe can expand forever or collapse again depending on mean matter density Georges Lemaitre P Belgian 1927 rediscovers Friedmann solutions told Hubble observing redshifts since 1924 that cosmic expansion suggests more distant galaxies should have greater redshifts Hubble publishes V Hod in 1929 Einstein visited Hubble in 1932 said CC was the greatest blunder of his career l Very important diagram l The expansion rate of the universe is not necessarily constant for all time quotAverage distance LL Nl Different models for different amounts of dark matter HUbbe COHStant NOW i i i Let s ignore aoceleratingfor sets how fast now i l l past D universe IS past lime billions or years future expanding NOW Big Bang when distance zero between 39 a gaaXIes GRAVITY should SLOW v measure of E expansion rate 9 expansion factor E deceleratlon of Universe ll D average distance between galaxies Critical Universe Slnce graVIty Is what pulls everythlng Flawnlverse back in there must be a magic number Density of Just the right amount of mass in our current matter universe to slow down expansion but not critical Eb enough to cause recollapse density g We call this exact amount of matter the Will expand CRITICAL DENSITY forever but 9 103929 gramscm3 a few atoms in a closet more and 4g more slowly Y I with time quot0 past time billions of years future imam Was Recollapsing Universe Coasting Universe Closed Universe Ogen Universe Dark matter density is 499quot i The universe 9quot greater than has always g critical density expanded at the same rate no deceleration Expansion will due to gravity average distance between galaxies average distance between galax stop in the future will collapse back 39 Th 899 0fthe in I Universe 1Ho Big Crunch i i ii 3 i i ii i 39f Oscillations 4 time billions of years future time billions of years future epvnelii amuse viiislay Clicker Question Three models for fates of universe Which model predicts the largest age for the universe today A Recollapsing closed B Critical flat C Coasting Open average distance between galaxies C Coasting Age of universe is how far to left average distance between galaxies curves hit E 5 horizontal axis distance 3 between 39 l galaxies0 past time billions of years future Which is it Is there enough dark matter to recolapse the universe Baryonic matter only a few of critical density Dark matter only about 25 of what is needed 7 Universe should be in between the coasting and critical models The Universe will expand forever and with an unexpected twist What is the fate of the Universe Recollapse to big crunch Crushing heat Destruction of all matter Rebirth Eternal expansion Cold galaxies dimming Star formation slowing Everything winds up as a brown dwarf black dwarf neutron star or black hole A New Twist for the 21st Century Host Galaxies of Distant Supernovaa Scientists using white dwarf supernovae to measure distances discovered something quite strange NASA ESA andA Riess ljSTScl Supernovae are not consistent even with USIng SUpemovae to determine the expectations of a coasting universe the fate of the Universe Redshifts of the supernovae gives their vertical position Space has stretched since they gave off their supernova data based on redshift based on redshift average distance belweeri galaxies average distance between gaIaXies light Apparent brightness gives 1 ng 40 i I 0 1 0 39 39 their horizontal 30 88 44pasw we quot3390 8 8 quot1394 pasts iame I gme ib mogowear v timein billlonsolyears Dimmermore b22833quotaggs en gi 22383 Sg ii i39iiig il39i i i i d39 t t h39 h lgif ack 399 Universe is accelerating HOW can the universe be our models for fates of universe accelerating A force that counteracts gravity 39e n lli iiiig 123539 33522 Dark energy outweighs every other form of massenergy Truly an unknown force in all of phvsics The Cosmological Constant actually exists Check out Einstein s Greatest Blunderquot p 679 Clicker Question Clicker Question What is meant by dark energy What is meant by dark energy A The energy associated with dark matter through A The energy associated with dark matter through Emc2 Emc2 B An unknown form of energy that counteracts B An unknown form of energy that counteracts gravity and causes the expansion ofthe gravity and causes the expansion ofthe universe to accelerate universe to accelerate C Any unknown force that acts like gravity C Any unknown force that acts like gravity D Highly energetic particles that are believed to D Highly energetic particles that are believed to constitute dark matter constitute dark matter E The total energy in the universe afterthe Big E The total energy in the universe afterthe Big Bang but before the first stars Bang but before the first stars Disk Bulge amp Halo Disk includes spiral arms REVIEW FOR MID TERM In young newstar to follow formation 4 globular clusters Bulge amp Halo older stars globular clusters halo Vspiral arms I Artist 3 sketch halo star orbits green Disk iS very thin bulge sfar39orbitsqed 1 39disk 39Sun s bulge halo location 1000lightyears A I Iglobular 28000 light years clusters disk star orbits 39 yellow lt39 39 100000 lightyears Galaxies Ultimate Recying Plants Summary of Galactic Recycling From HOT to COLD atomicrhydrogcn d 7 2 51 A Stars make new elements by fusion E j bbles m39mewmm w Dying stars expel gas and new elements producing m m m M 73 hot bubbles 106 K A Slar Gas Slar Hot gas cools allowing atomic hydrogen clouds to CV 5 form 100 10000 K ramming gas spupgmovaexand siariovmaim Further cooling permits molecules to form making stelldi Wlndb w my rig sicllarlives 39 nuclear lusion heavyreiem loinialloil molecular clouds 30 K Gravity forms new stars and planets in molecular clouds E 39 enl Ln We observe star gas star cycle operating in Milky Way s disk using many different wavelengths of light a 27min radii goings on iron39 atlzjr39m l iu39r3r39rggequotl 433 5 I W 4quot quotruJ39 4 n 39 391 r 39 ww 0 g Germs rajquot common lror39i CC I 313quot 1quot cosmc rays mtl o Tom c quotllJClD 11 quotMetre lnr C Duds CV 801 302 0 304 305 0 3016 0 3019 0 3020 KeckchA Galactic Center G 19952006 orbiting something massive but invisible a black hole Orbits of stars indicate a mass of about 3 4 million Msun within 600 RSchwarzchild Dark matter halo for galaxies Dark matter extends beyond visible part of the galaxy mass is 10x stars and gas dark matter luminous matter Probably not normal mass that we know of protons neutrons electrons Most likely subatomic particles as yet unidenti ed weakly interacting massive particles WIMPs Summary Distance Ladder to measure universe Q h l Tully FiShel l l relation if I 5 39 l 1 quot I l 39 l l n y m 5 white dwa 39 l l supernovae l4 MUM quot 1r l U o l S quot iS Different standard candles are useful for different distances Balloon analogy for expanding universe Hubble s Law reoessionai velocity kms ll elocity of Hubbleas Distance EaCh dot on the ecesswn Doppler Shift mm balloon can be kmsec kmsecMpc Mpc of a S a 39 galaxy 3 x I0 7 0 1 Best current Assivgdzvxqo values for As the balloon 0 W i f expansion expands galaxies tquot move farther away 0 Ho 4 from each other 3 distance kmSMpc Ooj II I Inion I I I2OI I I Iatiml I I I4iJOI I I I500 apparent distance Mpc Forming a M with spiral As more material collapses angular momentum spins it into a disk Making ellipticals 1 Higher density much faster star formation uses up all the gas Nothing left to make a disk or 2 Lower spin Gas used up before angular momentum took over Stars now formed in dense spiral m disk stars are younger Now we see a sphere of old stars An ular momentum of roto alactic important in spiral galaxy formation 39 39 Or perhaps a different scenario AGNS Central Engines SQiral galaxy collisions destroy disks leave behind elliQtical HOW d0 AGNS emit so much light in so little space Burst of star formation uses up all the gas They are powered by accretion disks around supermassive black holes Leftovers train wreck Ellipticals more common in dense galaxy clusters centers of clusters contain central dominant galaxies In some AGNs huge jets of material are shot i out at the poles These jets are strong radio sources Central Engine artist s prototypical Accretion disk radio galaxy around super massive black Ole Giant elliQtical ga x NGC 5128 Disk itself may or with dust lane may not be obscured by dust fromspiral galaxy W If bright nucleus is radio source visible looks like a color lobes guasar if not then its a radio galaxy


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