1. The Life History of Stars – High Mass
Outline
Mommy
Molecular Cloud
Protostar
Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole
Fetus
Adult
Old Man
Heart Attack
Corpse

2. 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

3. Supergiant Stages Supergiant Stages Hydrogen Helium Carbon/Oxygen Neon
Molecular Cloud
Protostar
Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole
Hydrogen
Helium
Carbon/Oxygen
Neon
Silicon
Iron

4. Stages Go Steadily Faster – 25 MSun star
Molecular Cloud
Protostar
Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole
Stage Fuel Time
Main Sequence Hydrogen 7 Myr
CHB/DSB Helium 700 kyr
Carbon 600 yr
Neon 1 yr
Oxygen 6 months
Silicon
Supergiant Stages
Late Stages
Q. 80: Extrapolating the Length of Stages

5. Stages Go Steadily Faster – 25 MSun star
Molecular Cloud
Protostar
Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole
Stage Fuel Time
Main Sequence Hydrogen 7 Myr
CHB/DSB Helium 700 kyr
Carbon 600 yr
Neon 1 yr
Oxygen 6 months
Silicon 1 day
(Collapse) Iron (?) 1 second
Supergiant Stages
Late Stages
Iron can’t burn – it is completely “burned”
When it hits the Chandrasekhar limit, it will collapse under its own weight

6. Core Collapse + + Molecular Cloud Iron Core begins to collapse
Protostar
Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole
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 + +

7. Core Bounce P  n5/3/m Q. 81: Neutron Degeneracy Pressure
Eventually, the neutron’s degeneracy pressure kicks in
Core slams to a stop in 1 millisecond
Rings like a bell
Temperature soars 1 trillion K
Over next 10 seconds, energy pours out in the form of (invisible) neutrinos
More than rest of Universe!
Shock wave expands outwards and destroys star
P  n5/3/m
Q. 81: Neutron Degeneracy Pressure

8. Massive Star Supernova
Protons, Neutrons, Electrons
Molecular Cloud
Protostar
Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole
Iron Core
Neutron Star
Core Bounce
Shock Waves

9. Massive Star Supernova
Molecular Cloud
Protostar
Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole
Supergiant Stages
Hydrogen
Helium
Carbon/Oxygen
Neon
Silicon
Iron

10. After the Supernova Molecular Cloud
Protostar
Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole
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

11. Supernovae
SN1994 D

12. Supernova 1987a
SN1987A

13. Supernova Remnant – Crab Nebula

14. Supernova Remnant – Crab Nebula

15. Supernova Remnant – Crab Nebula
Near Ultraviolet
Far Ultraviolet
Visible
X-Rays

16. Tycho’s Supernova Remnant
X-Rays
X-Rays Plus Infrared

17. Supernova Remnants
Veil Nebula
Puppis A

18. Supernova Remnants
N49
W49B
Kepler SNR

19. Supernova Remnants
Tarantula Nebula

20. Supernova Remnants – Vela Nebula

21. Supernova Remnants – DEM L316

22. Neutron Stars Molecular Cloud Structure Protostar Pure neutrons5 10 15 20
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 mass 2 – 3 MSun
Size
Typically 25 km
More massive smaller

23. Neutron Stars Molecular Cloud Protostar Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole

24. Pulsars Q. 82: Pulsars Molecular Cloud Protostar Most stars spin
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
Q. 82: Pulsars

25. Pulsars
Crab Pulsar Optical and X-ray

26. Forming a Black Hole Very massive stars (>30 MSun) Molecular Cloud
Core gets too heavy and collapses to neutron star
Outer layers not completely blown away – 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
Molecular Cloud
Protostar
Main Sequence
Supergiant Stages
Massive Star Supernova
Neutron Star or Black Hole

27. Einstein’s Theories of Relativity
Singularity
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
Help!
Event Horizon

28. 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