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

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

Stages Go Steadily Faster – 25 M Sun star Molecular Cloud Protostar Main Sequence Supergiant Stages Massive Star Supernova Neutron Star or Black Hole StageFuelTime Main SequenceHydrogen7 Myr CHB/DSBHelium700 kyr Carbon600 yr Neon1 yr Oxygen6 months Silicon1 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 Stages

Core Collapse Iron Core begins to collapse Iron disintegrates P  n 5/3 /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 it B) Neutron is much more massive C) Neutrons are neutral – no electric repulsion Core Bounce P  n 5/3 /m 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

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 Hydrogen Helium Carbon/Oxygen Neon Silicon Iron 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

Near UltravioletFar Ultraviolet Visible X-Rays Supernova Remnant – Crab Nebula

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

Puppis A Veil Nebula Supernova Remnants

W49B N49 Kepler SNR Supernova Remnants

Tarantula Nebula Supernova Remnants

Supernova Remnants – Vela Nebula

Supernova Remnants – DEM L316

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 M Sun Maximum mass 2 – 3 M Sun 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

Pulsars Crab 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 M Sun ) 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

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 v e = c You can’t escape if you are closer than: The event horizon Event Horizon Singularity Help!

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