The Life History of Stars – High Mass Outline •Molecular Cloud Mommy
advertisement
The Life History of Stars – High Mass Outline •Molecular Cloud Mommy •Protostar Fetus •Main Sequence Adult •Supergiant Stages Old Man •Massive Star Supernova Heart Attack •Neutron Star or Black Hole 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 Supergiant •Protostar Stages •Main Sequence •Supergiant Stages •Massive Star Supernova Hydrogen •Neutron Star or Helium Black Hole Carbon/Oxygen Neon Silicon Iron Stages Go Steadily Faster – 25 MSun star Time 7 Myr 700 kyr 600 yr 1 yr 6 months 1 day 1 second Supergiant Stages Stage Fuel Main Sequence Hydrogen CHB/DSB Helium Carbon Late Neon Stages Oxygen Silicon (Collapse) Iron (?) •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 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 Core Bounce •Eventually, the neutron’s P n5/3/m degeneracy pressure kicks in How come the neutron’s •Core slams to a stop in 1 degeneracy pressure doesn’t millisecond support the core from collapse? •Rings like a bell •Temperature soars 1 trillion K A) Neutrons don’t have it •Over next 10 seconds, energy B) Neutron is much more massive pours out in the form of C) Neutrons are neutral – no (invisible) neutrinos •More than rest of Universe! electric repulsion •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 •Molecular Cloud Supergiant •Protostar Stages •Main Sequence •Supergiant Stages •Massive Star Supernova Hydrogen •Neutron Star or Helium Black Hole 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 SN1994 D Supernova 1987a SN1987A 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 X-Rays Plus Infrared Supernova Remnants Veil Nebula Puppis A Supernova Remnants N49 W49B Kepler SNR Supernova Remnants Tarantula Nebula Supernova Remnants – Vela Nebula Supernova Remnants – DEM L316 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 •Molecular Cloud •Most stars spin •Protostar •Shrinking core spins faster •Main Sequence •Magnetic fields, trapped, get concentrated •Supergiant Stages •Whirling strong magnet •Massive Star •Charged particles get whipped around by Supernova magnet - they radiate •Neutron Star or •Lighthouse effect Black Hole 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 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 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: Event 2GM 2GM 2 R 2 Horizon ve R ve •You can’t escape when ve = c •You can’t escape if you are closer than: •The event horizon 2GM M Re c 2 Re M 3 km 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
