The Life History of Stars – High Mass Outline Molecular Cloud Protostar Main Sequence Supergiant...
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Transcript of The Life History of Stars – High Mass Outline Molecular Cloud Protostar Main Sequence Supergiant...
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
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
Supergiant Stages
HydrogenHeliumCarbon/OxygenNeonSiliconIron
•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
Supergiant Stages
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
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
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
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
Massive Star Supernova
HydrogenHeliumCarbon/OxygenNeonSiliconIron
•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
Supergiant Stages
•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
Supernovae
SN1994 D
Supernova 1987a
SN1987A
Supernova Remnant – Crab Nebula
Supernova Remnant – Crab Nebula
Near Ultraviolet Far Ultraviolet
VisibleX-Rays
Supernova Remnant – Crab Nebula
X-RaysX-Rays Plus Infrared
Tycho’s Supernova Remnant
Puppis AVeil Nebula
Supernova Remnants
W49B
N49
Kepler SNR
Supernova Remnants
Tarantula Nebula
Supernova Remnants
Supernova Remnants – Vela Nebula
Supernova Remnants – DEM L316
0
5
10
15
20
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
Neutron stars•Molecular Cloud•Protostar•Main Sequence•Supergiant Stages•Massive Star Supernova•Neutron Star or Black Hole
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
PulsarsCrab Pulsar Optical and X-ray
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
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!
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