1ASTR 1040 ASTR 1040 AccelAccelAstroAstro: : Stars & GalaxiesStars & GalaxiesProf. Prof. JuriJuriToomreToomreTA: Nicholas NelsonTA: Nicholas NelsonLecture 14 Lecture 14 ThurThur24 Feb 201124 Feb 2011zeus.colorado.edu/astr1040zeus.colorado.edu/astr1040--toomretoomreStellar windsStellar windsfrom hot starfrom hot starTodayToday’’s s ““BizarreBizarre””EventsEvents••Helium flashHelium flashgoes off in shrinking degenerate core of red goes off in shrinking degenerate core of red giant: giant: horizontal branchhorizontal branchstar with He core burningstar with He core burning••Double shell burning (H and He) yields Double shell burning (H and He) yields red supergiantred supergiant(RG (RG II),II),blows off blows off planetary nebulaplanetary nebula••What doesWhat does““electron degeneracyelectron degeneracy””mean ?mean ?••Look at properties of Look at properties of white dwarfs white dwarfs as end of life cycle for as end of life cycle for low mass stars low mass stars ••Observatory Night #4 tonight, Observatory Night #4 tonight, Part BPart Bon spectroscopyon spectroscopy; ; writeupswriteupsdue Tues March 1 from due Tues March 1 from Part A observingPart A observing••Planet FinderPlanet Finderhelp sessionhelp sessionin computer lab Gin computer lab G--116 today, 116 today, 1pm1pm--3pm, by Nick Nelson; overview later in lecture3pm, by Nick Nelson; overview later in lecture••ReadRead17.317.3Life as HighLife as High--Mass StarMass Starand and 17.4 17.4 Roles of Mass Roles of Mass Exchange and Exchange and 18.118.1White DwarfsWhite DwarfsClicker Clicker ––Stellar EvolutionStellar Evolution••Which is correct order for some Which is correct order for some stages of stages of lifelifein a lowin a low--mass star? mass star? ••A.A.protostarprotostar, main, main--sequence star, red giant, sequence star, red giant, planetary nebula, white dwarfplanetary nebula, white dwarf••B.B.protostarprotostar, main, main--sequence star, red giant, sequence star, red giant, supernova, neutron starsupernova, neutron star••C.C.mainmain--sequence star, white dwarf, red giant, sequence star, white dwarf, red giant, planetary nebula, planetary nebula, protostarprotostar••D.D.protostarprotostar, main, main--sequence star, planetary sequence star, planetary nebula, red giant nebula, red giant A.A.MS MS Red Giant I Red Giant I HorizHorizBranch Branch Red Giant IIRed Giant II(or Supergiant)(or Supergiant)MSMSRG IRG IRG IIRG II““Life trackLife track””of of solarsolar--mass starmass starREMINDERREMINDER2:2:SubgiantSubgianttotoRed GiantRed Giant(first visit)(first visit)H burning in H burning in shell,shell,makes much moremakes much moreenergyenergyVast expansion,Vast expansion,RG phase lastsRG phase lasts~ 500 MY~ 500 MYHuge convectiveHuge convectiveenvelopeenvelopeREMINDERREMINDERMS MS subgiantsubgiantred giantred giantContracting core in red giant gradually becomes Contracting core in red giant gradually becomes ““electron degenerateelectron degenerate””----what does that mean?what does that mean?MSMSred giantred giant2ThermostatThermostatis is missingmissinginindegenerate gasdegenerate gasCould beCould bemore thanmore thanexciting!exciting!REMINDERREMINDER3:3:Helium Helium FlashFlashHe He corecoreburning burning ----removes electron removes electron degeneracydegeneracy••He core burningHe core burningnow with thermostat !now with thermostat !••““horizontalhorizontalbranch starbranch star””4:4:HorizontalHorizontalbranch starbranch starHe core burning,He core burning,H shell burningH shell burningShort phase,Short phase,lasts ~50 MYlasts ~50 MYTripleTriple--alpha alpha fusionfusion: : 3 He 3 He CCHelium flash Helium flash He fusion to CHe fusion to Cin core in core (horizontal branch)(horizontal branch)HH--R diagram ofR diagram ofglobular clusterglobular clusterDiscussionDiscussion::““City of StarsCity of Stars””::What does itWhat does ittell us? Why istell us? Why isit useful?it useful?5.5.RedRedSupergiantSupergiantDoubleDouble--shellshellburningburningofofH and HeH and HePhase could bePhase could bevery short if very short if He He burning is erraticburning is erratic(unstable)(unstable)----then lasts onlythen lasts onlya few MY, anda few MY, andblows off outerblows off outershellsshells3Sun in itsSun in its““far futurefar future””~5+ BY~5+ BYThermal pulses inThermal pulses inred supergiantred supergiantblowblowoff outer shellsoff outer shellsradiusradiusluminosityluminosityLife trackLife trackin in HH--R diagramR diagramof of solarsolar--massmassstarstarMany meandersMany meanders,,but MS phasebut MS phaselongestlongest, , red giantred giantphase(sphase(s) shorter) shorter,,finally white dwarffinally white dwarfleft to cool slowlyleft to cool slowlyprotostarprotostarblow lovely shellblow lovely shellZAMSZAMSwhite dwarfwhite dwarfRed Giant IRed Giant IRG IIRG II??Brightness / Distance Brightness / Distance Clicker Q Clicker Q ••Leonardo and Guinevere are two stars Leonardo and Guinevere are two stars that have the that have the same apparent brightness.same apparent brightness.Leonardo has a Leonardo has a larger parallax anglelarger parallax anglethan Guinevere. Which star is more than Guinevere. Which star is more luminous?luminous?••A.A.LeonardoLeonardo••B.B.GuinevereGuinevere••C.C.Cannot determine from data givenCannot determine from data givenB.B.••Leonardo has a Leonardo has a larger parallax anglelarger parallax angle----thus he is closer to usthus he is closer to us••They both have the same APPARENT They both have the same APPARENT brightness, but Leo is closerbrightness, but Leo is closer••B.B.GuinevereGuineveremust be more luminousmust be more luminousBrightness / DistanceBrightness / DistanceClicker Poll of Advice Clicker Poll of Advice ••How do you take notes (or listen) during How do you take notes (or listen) during lectures?lectures?••A. I get most of it by just listeningA. I get most of it by just listening••B. I write down some notes, then go back to B. I write down some notes, then go back to book to look things upbook to look things up••C. I listen, take some notes, then get copies of C. I listen, take some notes, then get copies of lecture slides from course websitelecture slides from course website••D. I enjoy talking with my buddies, and they tell D. I enjoy talking