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ASTR 1040 Accel ASTR 1040Accel AstroAstro:: Stars & GalaxiesStars & Galaxies
Prof.Prof. JuriJuri ToomreToomre^ TA: Kyle AugustsonTA: KyleAugustson
Lecture 17Lecture 17 Tues 11 Mar 08Tues 11 Mar 08
zeus.colorado.edu/astr1040-zeus.colorado.edu/astr1040-toomretoomre
CasCas A SNRA SNR VLAVLA -- radioradio
Today in BizarreToday in Bizarre--LandLand
- •^ Turn to evolution ofTurn to evolution of^ massive starsmassive stars^ throughthrough^ giantgiant and supergiant phasesand supergiant phases:: fusion occurs infusion occurs in
successive layers of onion’successive layers of onion’ - •^ End life asEnd life as^ supernova explosionsupernova explosion, leaving behind, leaving behind eithereither neutron starneutron star oror black holeblack hole
- • PulsarsPulsars – – fast spinning neutron stars with fiercefast spinning neutron starswith fierce magnetic fields; gradually slow downmagnetic fields; gradually slow down
- • Synchrotron radiationSynchrotron radiation makes the light seen asmakes the light seen as pulses –pulses– and thus Crab nebula + pulsar shinesand thus Crab nebula + pulsar shines (and pulses) brightly in many wavelengths(and pulses) brightly in many wavelengths
- • ReadRead 18.2 Neutron Stars18.2Neutron Stars andand 18.3 Black Holes18.3Black Holes
- •^ RecallRecall^ Second MidSecond Mid--TermTerm^ Mon 17 Mar;Mon 17 Mar;^ ReviewReview Thur 13 Mar 7 Thur13 Mar 7--9pm;9pm; ObservatoryObservatory # 4# 4 Wed 12 MarWed 12 Mar 8- 8 -10pm (signup)10pm (signup)
Binary Systems: TheBinary Systems: The AlgolAlgol ParadoxParadox
- •^ AlgolAlgol is ais a binary systembinary system consisting of a 3.7consisting of a 3.
solar masssolar mass main sequence starmain sequence star and a 0.8and a 0.
solar masssolar mass red giantred giant. Why is this strange?. Why is this strange?
- • A.A. A 3.7 star should have become a red giant before a 0.8 solar mass star
- • B.B. Binary stars usually have the same mass
- • C.C. 0.8 solar mass stars usually never become red giants
A.A.
Clicker Puzzle: AlgolClicker Puzzle: Algol Binary SystemBinary System
- •^ A.A.^ Binary stars canBinary stars can have different masseshave different masses but usually AREbut usually ARE formed at the sameformed at the same time.time.
- • More massive starMore massive star should have had ashould have had a shortershorter mainmain sequence lifetimesequence lifetime
What happened?What happened?
- • The 0.8 solar mass star onceThe 0.8 solar mass star once was more massive (3.0), withwas more massive (3.0), with a 1.5 mass companiona 1.5 mass companion
- • (^) As it became aAs it became a red giantred giant, it, it swelled and poured materialswelled and poured material onto its companion (lost 2.2)onto its companion (lost 2.2)
- • (^) TheThe red giantred giant (0.8) is now(0.8) is now less massive than itsless massive than its companion (3.7)companion (3.7)
- • (^) FutureFuture: when the other star: when the other star becomesbecomes red giantred giant, it may, it may pour gas backpour gas back……??
Binary Mass Exchange Binary Mass Exchange 3.03.0 1.51.
0.80.8^ 3.73.
early MSearly MS
nownow
Overview reminder:Overview reminder: Life track of lowLife track of low--mass starmass star
ClickerClicker ---- Paths in HPaths in H--R DiagramR Diagram
• •^ Star movesStar moves upwards and to the rightupwards and to the right on theon the
HH--R diagram. What is probably happeningR diagram. What is probably happening
in thein the corecore??
A.A. Core has just started to burn a newCore has just started to burn a new
elementelement
B.B. Inner core is contracting and heating up;Inner core is contracting and heating up;
shell burning is increasingshell burning is increasing
C.C.^ All nuclear burning is slowing downAll nuclear burning is slowing down
D.D.^ The inner core temperature is coolingThe inner core temperature is cooling
B. B.
HR diagram shiftsHR diagram shifts
• • B.B. Core is contracting and heating; shellCore is contracting and heating; shell
burning is increasingburning is increasing
• •^ Moving upwards on HR diagram meansMoving upwards on HR diagram means
more luminositymore luminosity ÆÆ more nuclear fusionmore nuclear fusion
• • This is usually due to the inner coreThis is usually due to the inner core
heating due to gravitational collapseheating due to gravitational collapse
potentialpotentialÆ Æ thermalthermal ÆÆ faster burningfaster burning
Upward and to the right in H- Upward and to the right in H-R:R:
Giant phases in life track of lowGiant phases in life track of low--mass starmass star LuminosityLuminosity
(solar units)(solar units)
ÅÅ^ TemperatureTemperature
1010 - -4^4
Now considerNow consider evolution ofevolution of massive starsmassive stars after MSafter MS
Evolution ofEvolution of
massive starsmassive stars
Clock runs fasterClockruns faster,,
can burn heaviercan burn heavier elementselements
First 4 stepsFirst4 steps prettypretty familiar, but nofamiliar, butno helium flashhelium flash
SuccessiveSuccessive core & shellcore & shell fusion burningfusion burning of C, O, Ne, Si ..of C, O, Ne, Si ..
all withall with ““alpha capturealpha capture”” (or He)(or He)
stars make manystars make many shallow Hshallow H--R loopsR loops
5.5.
6.6.
MassiveMassive red giantred giant or supergiant:or supergiant:
Fierce hotFierce hot winds andwinds and pulsedpulsed ejectaejecta
Hubble STHubble ST
Wildest of all !Wildest of all!
ETA CARINAEETA CARINAE
SupermassiveSupermassive star (100 Mstar (100 M SUNSUN )) late in life,late in life, giant outburstgiant outburst 150 yr ago150 yr ago
Violent bipolarViolent bipolar ejectaejecta + disk+ disk at equatorat equator
Star V838 Star V MonocerotisMonocerotis HST-HST-ACSACS
Light EchoLight Echo’’ from pulsefrom pulse
Red GiantRed Giant or SG withor SG with intenseintense brighteningbrightening
Evolution of V838 Light Echo (HST)Evolution of V838 Light Echo (HST)
““OnionOnion--shell fusion burningshell fusion burning”” stops withstops with
IRON (Fe, 26 protons )IRON(Fe, 26 protons )
Iron does NOTIron does NOT release energyrelease energy when it fuses !when it fuses!
FUSIONFUSION FISSIONFISSION
CARTOONCARTOON
Actual “Actual“mass / nuclear particlemass / nuclear particle””
FUSION FUSION FISSIONFISSION
Iron does NOTIron does NOT release energyrelease energy when it fuses !when it fuses!
Several fatesSeveral fates for massive starfor massive star
1.1. Strong winds shrinkStrong windsshrink star, may end asstar, may end as WHITE DWARFWHITE DWARF
2.2. Or core burns to Fe,Or core burns to Fe, eventually suddeneventually sudden CORE COLLAPSE !CORE COLLAPSE!
SUPERNOVASUPERNOVA
““Core Collapse SUPERNOVACore Collapse SUPERNOVA””
- • Exploding remnantExploding remnant ofof massive starmassive star disperses heavydisperses heavy elements throughelements through the galaxythe galaxy
- • Inside may be aInside may be a neutron starneutron star –– aa remnant core ofremnant core of pure neutrons!pure neutrons!
Crab Nebula (M1),Crab Nebula (M1), first seen as SUPERNOVAfirst seen as SUPERNOVA on 4 July 1054 from Chinaon 4 July 1054 from China ---- visible in daytimevisible in daytime
““Core collapseCore collapse”” (massive star)(massive star) SUPERNOVASUPERNOVA
“Rapid disassembly“Rapid disassembly”” of elements in coreof elements in core Æ Æ neutronsneutrons
Neutron degeneracyNeutron degeneracy pressurepressure stiffensstiffens collapsing corecollapsing core ------ ++ push of neutrinospush of neutrinos
ÆÆenvelope bounces’envelopebounces’ !! ÆÆSHELL BLOWS OFFSHELL BLOWS OFF
SNR:SNR: CrabCrab NebulaNebula M1M
4 July 10544 July 1054
Crab SNRCrab SNR compositecomposite Oct 06:Oct 06: Spitzer (IR),Spitzer (IR), Chandra (X),Chandra (X), Hubble (V)Hubble (V)
Observing SupernovaeObserving Supernovae
- • About 1 per century perAbout 1 per century per galaxy (none in Milkygalaxy (none in Milky Way since 1604Way since 1604 –– KeplerKepler)) [1572[1572 –– Brahe; 1054Brahe; 1054 –– Crab; 1004Crab; 1004 –– brightest]brightest]
- • BrightBright explosionexplosion visiblevisible for weeks/monthsfor weeks/months -- somesome visible in daytime!visible in daytime!
- •^ RemnantRemnant visible forvisible for 10,000+ years as huge10,000+ years as huge bubbles andbubbles and ““veilsveils”” –– longer inlonger in radioradio
Pulsars and Neutron StarsPulsars and Neutron Stars
Pulsars are lighthousesPulsars are lighthouses in our Galaxy!in our Galaxy!
Why pulsars spin so fast:Why pulsars spin so fast:
Vast shrinking conserves angular momentumVast shrinking conserves angular momentum
- • Collapse to a neutronCollapse to a neutron starstar increases bothincreases both rotation and magneticrotation and magnetic fieldsfields
- •^ Newly collapsedNewly collapsed neutron stars canneutron stars can rotaterotate hundreds tohundreds to thousands of timesthousands of times per secondper second !!
Mystery resolved when Mystery resolvedwhen
pulsar discovered inpulsar discovered in Crab Nebula (knownCrab Nebula (known to be supernova remnant)to be supernova remnant)
---- Messier 1 or M1 !Messier 1 or M1!
The Crab pulsar alsoThe Crab pulsar also pulses in visual lightpulses in visual light
