The Life History of Stars – High Mass
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Transcript of The Life History of Stars – High Mass
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The Life History of Stars – High MassOutline
•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
MommyFetusAdultOld Man
Heart AttackCorpse
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Supergiant Stages•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
Variety of fuels burned in massive stars:•Main Sequence: Hydrogen Helium•CHB/DSB: Helium Carbon/Oxygen•More stages:•Carbon Neon•Neon Silicon, Oxygen•Oxygen Silicon•Silicon Iron
•Each stage produces less energy than the last•Each stage goes faster than the last
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Supergiant Stages
HydrogenHeliumCarbon/OxygenNeonSiliconIron
•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
Supergiant Stages
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Stages Go Steadily Faster – 25 MSun star
•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
Stage Fuel TimeMain Sequence Hydrogen 7 MyrCHB/DSB Helium 700 kyr
Carbon 600 yrNeon 1 yrOxygen 6 monthsSilicon 1 day
(Collapse) Iron (?) 1 second
Late Stages
•Iron can’t burn – it is completely “burned”•When it hits the Chandrasekhar limit, it will collapse under its own weight
Supergiant S
tages
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Core Collapse•Iron Core begins to collapse•Iron disintegrates•P n5/3/m
•Electron degeneracy pressure enormous•Will do anything to get rid of electrons
•Electron + proton neutron + neutrino
•Electrons (and protons) disappear•Pure neutrons
+ +
•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
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How come the neutron’s degeneracy pressure doesn’t support the core from collapse?A) Neutrons don’t have itB) Neutron is much more massiveC) Neutrons are neutral – no electric repulsion
Core Bounce
P n5/3/m•Eventually, the neutron’sdegeneracy pressure kicks in
•Core slams to a stop in 1millisecond•Rings like a bell
•Temperature soars 1 trillion K•Over next 10 seconds, energypours out in the form of(invisible) neutrinos
•More than rest of Universe!•Shock wave expands outwards and destroys star
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Iron Core
Protons, Neutrons, Electrons
Core Bounce
Shock Waves
Neutron Star
Massive Star Supernova•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
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Massive Star Supernova
HydrogenHeliumCarbon/OxygenNeonSiliconIron
•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
Supergiant Stages
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•Expanding shock wave slams through the rest of the star
•Takes several hours•Every other element is produced
•Most of the mass of the star – including many heavy elements – get recycled back into the Universe – a Supernova Remnant
•The Earth is made of star stuff•The ball of neutrons – a neutron star – remains at the center
After the Supernova•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
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Supernovae
SN1994 D
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Supernova 1987a
SN1987A
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Supernova Remnant – Crab Nebula
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Supernova Remnant – Crab Nebula
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Near Ultraviolet Far Ultraviolet
VisibleX-Rays
Supernova Remnant – Crab Nebula
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X-RaysX-Rays Plus Infrared
Tycho’s Supernova Remnant
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Puppis AVeil Nebula
Supernova Remnants
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W49B
N49
Kepler SNR
Supernova Remnants
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Tarantula Nebula
Supernova Remnants
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Supernova Remnants – Vela Nebula
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Supernova Remnants – DEM L316
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Neutron stars•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
•Structure•Pure neutrons•Held up by neutron degeneracy pressure
•Mass•Most around 1.4 MSun
•Maximum mass2 – 3 MSun
•Size•Typically 25 km •More massive smaller
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Neutron stars•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
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Pulsars•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
•Most stars spin•Shrinking core spins faster
•Magnetic fields, trapped, get concentrated•Whirling strong magnet
•Charged particles get whipped around by magnet - they radiate
•Lighthouse effect
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PulsarsCrab Pulsar Optical and X-ray
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Forming a Black Hole•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
Very massive stars (>30 MSun)•Core gets too heavy and collapses toneutron star•Outer layers not completely blownaway – they fall back towards the star•Mass exceeds maximum mass•Gravity exceeds pressure•Star collapses again
•Once it reaches its event horizon, nothing can stop it•It becomes a black hole
•Infinite density
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Einstein’s Theories of Relativity•Special Theory of Relativity
•Says nothing can go faster than light•General Theory of Relativity
•Describes gravity•Using Newton: Escape velocity:
•You can’t escape when ve = c•You can’t escape if you are closer than:
•The event horizon
2 2e
GMv
R
2
2e
GMR
c
2
2
e
GMR
v
3 kme
MR
M
Event Horizon
SingularityHelp!
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Gamma Ray Bursters•There are intense bursts of gamma rays
•Typically last about 30 seconds•Brighter than a supernova
•Followed by “fireball” of visible light•Followed by a massive star supernova explosion•Cause is probably very massive star death and creation of black hole
•They occur in galaxies•Typically, galaxies have lots of young stars in them