The Life History of Stars – High Mass

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

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

4. Stages Go Steadily Faster – 25 MSunstar Late Stages • Molecular Cloud • Protostar • Main Sequence • Supergiant Stages • Massive Star Supernova • Neutron Star or Black Hole StageFuelTime 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 • Iron can’t burn – it is completely “burned” • When it hits the Chandrasekhar limit, it will collapse under its own weight

5. Core Collapse • Molecular Cloud • 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 + +

6. Core Bounce • 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 P n5/3/m How come the neutron’s degeneracy pressure doesn’t support the core from collapse? A) Neutrons don’t have it B) Neutron is much more massive C) Neutrons are neutral – no electric repulsion

7. 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

8. 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

9. 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

10. Supernovae SN1994 D

11. Supernova 1987a SN1987A

12. Supernova Remnant – Crab Nebula

13. Supernova Remnant – Crab Nebula

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

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

16. Supernova Remnants Veil Nebula Puppis A

17. Supernova Remnants N49 W49B Kepler SNR

18. Supernova Remnants Tarantula Nebula

19. Supernova Remnants – Vela Nebula

20. Supernova Remnants – DEM L316

21. Neutron stars 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 mass2 – 3 MSun • Size • Typically 25 km • More massive smaller 15 10 5 0

22. Neutron stars • Molecular Cloud • Protostar • Main Sequence • Supergiant Stages • Massive Star Supernova • Neutron Star or Black Hole

23. 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

24. Pulsars Crab Pulsar Optical and X-ray

25. 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

26. 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

27. 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