1ASTR 1040 ASTR 1040 AccelAccelAstroAstro::Stars & GalaxiesStars & GalaxiesProf. Prof. JuriJuriToomreToomreTA: Nicholas NelsonTA: Nicholas NelsonLecture 28 Lecture 28 ThurThur21 Apr 201121 Apr 2011zeus.colorado.edu/astr1040zeus.colorado.edu/astr1040--toomretoomreLargeLarge--scalescalestructurestructureCfACfAsurveysurveyJoys of Joys of ““Observational CosmologyObservational Cosmology””••More on More on Cosmic Microwave BackgroundCosmic Microwave Background••Look further atLook further atmodels for our universemodels for our universe, , and ideas of and ideas of ““dark energydark energy””arising from arising from whitewhite--dwarf supernova data + CMB dwarf supernova data + CMB mappingmapping••Next time: what occurs during Next time: what occurs during bigbig--bangbangbeginning + galaxy structuresbeginning + galaxy structures••Observatory Night # 8 tonightObservatory Night # 8 tonight8:30pm+8:30pm+••Course evaluation at end of class Course evaluation at end of class So what was with this exam?So what was with this exam?RESULTS FROM RESULTS FROM THIRD MIDTHIRD MID--TERM EXAMTERM EXAMTHIRD MIDTHIRD MID--TERM EXAMTERM EXAM••Grade boundariesGrade boundaries, based on 125 points:, based on 125 points:••If 111/125 (89%) or over, If 111/125 (89%) or over, AA’’ss[38%][38%]••102/125 (82%) or over, 102/125 (82%) or over, BB’’ss[40%][40%]••89/125 (71%) or over, 89/125 (71%) or over, CC’’ss[18%][18%]Also +, plain, and Also +, plain, and ––within these rangeswithin these rangesGo through answer sheetGo through answer sheet––and talk to us if and talk to us if do not understand our choices. Keep exam do not understand our choices. Keep exam + answers for future review (comp final)+ answers for future review (comp final)Rebecca Rebecca SeigelSeigel““Collimated Collimated Emission Emission AwardAward””Katherine Katherine ShanahanShanahan““Cosmic Web Cosmic Web AwardAward””2Light from beginning of timeLight from beginning of time••This faint light looks light a solid glowing wallThis faint light looks light a solid glowing wall••Thermal spectrum at 3000 KThermal spectrum at 3000 K, if , if redshiftedredshiftedby factor by factor ~1000 ~1000 microwavesmicrowaves!!COBECOBESpectrum of Cosmic Microwave Background (CMB)Spectrum of Cosmic Microwave Background (CMB)2.73 K `black body2.73 K `black body’’CMBCMBEVOLVINGEVOLVINGUNIVERSEUNIVERSESmall temperature fluctuationsSmall temperature fluctuationsused to used to test models of universetest models of universeone degree scale of bump one degree scale of bump ----> > flat universe with early inflationflat universe with early inflationWMAPWMAPHOT RESEARCH NOWHOT RESEARCH NOWVariations in CMB on small scalesVariations in CMB on small scalesFour models for fates of universeFour models for fates of universeCLOSEDCLOSEDOPENOPENNOWNOW3What is the fate of the Universe?What is the fate of the Universe?••RecollapseRecollapseto to gnaBgnaBgiBgiB::crushing heat, crushing heat, destruction of all matter (Big Crunch) destruction of all matter (Big Crunch) Rebirth ?Rebirth ?••Eternal expansionEternal expansion::cold, galaxies dimmingcold, galaxies dimmingstar formation slowing star formation slowing ••Everything winds up as a brown dwarfEverything winds up as a brown dwarfblack dwarf, neutron star or black holeblack dwarf, neutron star or black holeWhich is it ?Which is it ?Is there enough Is there enough dark matterdark matterto to recollapserecollapsethe universe?the universe?Baryonic matterBaryonic matter: only few % of critical density: only few % of critical densityDark matterDark matter: only about 25 % of what is needed: only about 25 % of what is neededUniverse is between the Universe is between the ““coastingcoasting””and and ““criticalcritical””modelsmodelsUniverse will expand foreverUniverse will expand forever(or so it seems)(or so it seems)New twistNew twistin the new in the new milleniummillenium••White dwarf White dwarf supernovaesupernovae::standard candles standard candles at Z ~ 1at Z ~ 1••Explosions bright Explosions bright enough to be seen enough to be seen very far away very far away (back in time)(back in time)Made especially possible by HST Made especially possible by HST SN Type SN Type IaIa::BIG DISCOVERYBIG DISCOVERYTHAT SHOOKTHAT SHOOKCOSMOLOGYCOSMOLOGYRedshiftsRedshiftsof the supernova of the supernova plot theirplot theirvertical positionvertical position••Z = 1 means Z = 1 means about halfway about halfway down from the down from the ““NOWNOW””levellevel••Expansion Expansion factor factor = 1 + Z = 2= 1 + Z = 2BrightnessBrightnessplots theirplots theirhorizontal positionhorizontal positionDimmer Dimmer = more distant = more distant = longer ago= longer ago••Supernovae are Supernovae are DIMMERDIMMERthan than expected for a expected for a coasting coasting universeuniverse••Universe is Universe is accelerating ??accelerating ??CLOSEDCLOSEDCRITICALCRITICAL(FLAT)(FLAT)OPENOPENTIMETIMESIZESIZENOWNOWModels of universe Models of universe ––and its fatesand its fates4How can universe be How can universe be acceleratingaccelerating????A force that counteracts A force that counteracts gravity?gravity?““Dark energyDark energy””––outweighs every other outweighs every other form of mass/energy!form of mass/energy!Truly an unknown force Truly an unknown force in all of physics!in all of physics!(Read (Read ““EinsteinEinstein’’s Biggest Blunders Biggest Blunder””Cosmological ConstantCosmological Constant--p 666)p 666)Clicker QuestionClicker Question••Which model predicts Which model predicts the the greatest agegreatest agefor for the universe today?the universe today?••A.A.RecollapsingRecollapsing(closed)(closed)••B.B.CriticalCritical(flat)(flat)••C.C.CoastingCoasting(open)(open)C.C.••C.C.CoastingCoasting••Age of universe Age of universe is how far to left is how far to left curves hit curves hit horizontal axis horizontal axis (distance (distance between between galaxies = 0)galaxies = 0)DoubleDouble--header clickerheader clicker••If there was really If there was really ZERO ZERO dark matterdark matterin the universe, in the universe, which model would which model would be the closest to be the closest to