The Life History of Stars High Mass Outline

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

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

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

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

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

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

Core Bounce • Eventually, the neutron’s degeneracy pressure kicks in – Core slams to a stop in 1 millisecond – Rings like a bell P n 5/3/m Q. 81: Neutron Degeneracy Pressure • 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

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

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

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

Supernovae SN 1994 D

Supernova 1987 a SN 1987 A

Supernova Remnant – Crab Nebula

Supernova Remnant – Crab Nebula

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

Tycho’s Supernova Remnant X-Rays Plus Infrared

Supernova Remnants Veil Nebula Puppis A

Supernova Remnants N 49 W 49 B Kepler SNR

Supernova Remnants Tarantula Nebula

Supernova Remnants – Vela Nebula

Supernova Remnants – DEM L 316

Neutron Stars • • • 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 20 15 10 5 0 • • • Molecular Cloud Protostar Main Sequence Supergiant Stages Massive Star Supernova Neutron Star or Black Hole

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

Pulsars • • 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 Molecular Cloud Protostar Main Sequence Supergiant Stages Massive Star Supernova Neutron Star or Black Hole Q. 82: Pulsars

Pulsars Crab Pulsar Optical and X-ray

Forming a Black Hole Very massive stars (>30 MSun) • 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

Einstein’s Theories of Relativity • Special theory of relativity – Says nothing can go faster than light Singularity • 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 Event Horizon 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