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ASTR 1040 ASTR 1040 AccelAccel AstroAstro: : Stars & GalaxiesStars & Galaxies

Prof. Prof. JuriJuri ToomreToomre TA: Nicholas NelsonTA: Nicholas NelsonLecture 14 Lecture 14 ThurThur 24 Feb 201124 Feb 2011

zeus.colorado.edu/astr1040zeus.colorado.edu/astr1040--toomretoomre

Stellar windsStellar windsfrom hot starfrom hot star

TodayToday’’s s ““BizarreBizarre”” EventsEvents•• Helium flashHelium flash goes off in shrinking degenerate core of red goes off in shrinking degenerate core of red

giant: giant: horizontal branchhorizontal branch star 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 B on spectroscopyon spectroscopy; ; writeupswriteups due Tues March 1 from due Tues March 1 from Part A observingPart A observing

•• Planet FinderPlanet Finder help sessionhelp session in 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

•• ReadRead 17.317.3 Life as HighLife as High--Mass StarMass Star and and 17.4 17.4 Roles of Mass Roles of Mass Exchange and Exchange and 18.118.1 White DwarfsWhite Dwarfs

Clicker Clicker –– Stellar EvolutionStellar Evolution•• Which is correct order for some Which is correct order for some stages of stages of

lifelife in 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 HorizHoriz Branch Branch Red Giant IIRed Giant II(or Supergiant)(or Supergiant)

MSMS

RG IRG I

RG IIRG II““Life trackLife track”” of of solarsolar--mass starmass star

REMINDERREMINDER

2:2: SubgiantSubgiant totoRed GiantRed Giant(first visit)(first visit)

H burning in H burning in shell,shell,makes much moremakes much moreenergyenergy

Vast expansion,Vast expansion,RG phase lastsRG phase lasts~ 500 MY~ 500 MY

Huge convectiveHuge convectiveenvelopeenvelope

REMINDERREMINDER

MS MS subgiantsubgiant red giantred giant

Contracting core in red giant gradually becomes Contracting core in red giant gradually becomes ““electron degenerateelectron degenerate”” ---- what does that mean?what does that mean?

MSMS red giantred giant

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ThermostatThermostatis is missingmissing inindegenerate gasdegenerate gas

Could beCould bemore thanmore thanexciting!exciting!

REMINDERREMINDER

3:3: Helium Helium FlashFlash

He He corecore burning burning ----removes electron removes electron degeneracydegeneracy

•• He core burningHe core burningnow with thermostat !now with thermostat !

•• ““horizontalhorizontalbranch starbranch star””

4:4: HorizontalHorizontalbranch starbranch star

He core burning,He core burning,H shell burningH shell burning

Short phase,Short phase,lasts ~50 MYlasts ~50 MY

TripleTriple--alpha alpha fusionfusion: : 3 He 3 He CC

Helium flash Helium flash He fusion to CHe fusion to C

in core in core (horizontal branch)(horizontal branch)

HH--R diagram ofR diagram ofglobular clusterglobular cluster

DiscussionDiscussion::““City of StarsCity of Stars””::What does itWhat does ittell us? Why istell us? Why isit useful?it useful?

5.5. RedRedSupergiantSupergiant

DoubleDouble--shellshellburningburning ofofH and HeH and He

Phase 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 outershellsshells

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Sun in itsSun in its““far futurefar future””

~5+ BY~5+ BY

Thermal pulses inThermal pulses inred supergiantred supergiant blowblowoff outer shellsoff outer shells

radiusradius

luminosityluminosity Life trackLife track in in HH--R diagramR diagramof of solarsolar--massmassstarstar

Many meandersMany meanders,,but MS phasebut MS phaselongestlongest, , red giantred giantphase(sphase(s) shorter) shorter,,finally white dwarffinally white dwarfleft to cool slowlyleft to cool slowly

protostarprotostar

blow lovely shellblow lovely shell

ZAMSZAMSwhite dwarfwhite dwarf

Red Giant IRed Giant I

RG 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 given

B.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. GuinevereGuinevere must be more luminousmust be more luminous

Brightness / DistanceBrightness / Distance

Clicker 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 with my buddies, and they tell

me later if I missed anythingme later if I missed anything

6.6. PlanetaryPlanetaryNebulaNebula

Outer shellsOuter shellsof red supergiantof red supergiant““puffed offpuffed off””

Great pictures!Great pictures!

““NakedNaked””white dwarfwhite dwarfemergesemerges

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Discussion for Tues:Discussion for Tues: ShapesShapes of Planetary Nebulaeof Planetary Nebulae

SpirographSpirographNGC 6751NGC 6751

CatCat’’s Eyes Eye Etched HourglassEtched Hourglass

NGC 7027NGC 7027 Ant Nebula Ant Nebula MzMz 33

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What is likely to account for the vast range What is likely to account for the vast range of shapes (many beautiful) of these of shapes (many beautiful) of these ejectaejecta? ?

Discussion for next TuesDiscussion for next Tues

Ring NebulaRing Nebula

Life after brief Life after brief ““planetary nebulaplanetary nebula””stage stage ……..

Hot central coreHot central coreemerges asemerges as

WHITE DWARFWHITE DWARF

7.7. White White DwarfDwarf

Inert C core,Inert C core,He & H shellsHe & H shells

electron degeneracyelectron degeneracypressure holds it uppressure holds it up

Very dense,Very dense,size of Earthsize of Earth

max mass ofmax mass of1.4 M1.4 MSUNSUN

Sizes of white dwarfsSizes of white dwarfs

More massive white dwarfs are More massive white dwarfs are SMALLERSMALLER !!

Final stage:Final stage:

CoolingCoolingwhite dwarfwhite dwarf------ snooze snooze ……..

MSMS

RG IRG I

RG IIRG II

NEBULANEBULA

WHITEWHITEDWARFDWARFBut if WD hasBut if WD has

binarybinarycompanioncompanion,,much fun canmuch fun canbegin !begin !

Overview reminder:Overview reminder: Life track of lowLife track of low--mass starmass star

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LuminosityLuminosity(solar units)(solar units)

TemperatureTemperature

101066

1010--44

40,00040,000 2,0002,000

Tues considerTues considerevolution of evolution of massive starsmassive starsafter MSafter MS

Hunting for ExtraHunting for Extra--Solar PlanetsSolar PlanetsDirect Imaging, Transiting, Direct Imaging, Transiting, Radial VelocitiesRadial Velocities

PLANET FINDER PROJECTPLANET FINDER PROJECT

Read Chap 13, Other Planetary SystemsRead Chap 13, Other Planetary Systems

Doppler wobble of central starDoppler wobble of central star

Radial velocity of 51 Radial velocity of 51 PegasiPegasi Doppler wobbles of other starsDoppler wobbles of other stars