Astronomy 113 Dr. Joseph E. Pesce, Ph.D.
Stellar Deaths/Endpoints
13-2 Low Mass Stars ³ Like the Sun (< 2 M ) ² Live about 10 billion years (sun is middle aged) ² Create elements through Carbon, Nitrogen, and Oxygen through fusion ³ Core uses up He, C & O left, reactions stop ³ Core collapses, shells of He and H ignite ³ Envelope expands (T down L up) ³ Becomes an Asymptotic Giant Branch star (AGB), very bright and enormous ³ Pulsations in core fusion rate (every ~300,000 years) blow away bloated atmosphere ³ Outer atmosphere cools, dust forms, shell of atmosphere ejected and hot core exposed, ionizing gas, causing it to glow ² A Planetary Nebula is formed q Expands to low density in ~50,000 yrs
13-3 Low Mass Stars AGB Planetary Nebula H He C,O L * He Flash C,O He T H He
13-4 Low Mass Stars ³ Matter is returned to ISM (it is enriched) ³ C-O core is never ignited, it s a left-over ember (white dwarf) ²Degenerate electrons, the size of the Earth ²Just cools thermally ²Very high density ²White dwarfs can t be more massive than 1.4 M = Chandrasekar Limit
13-5 The Life Cycle of a Low-Mass Star (After 10 billion years) ²Expands into a Red Giant (radius to ~Earth s orbit) ²Outer atmosphere blows off to become a Planetary nebula ²Burned out core left as a White dwarf
13-6 The Evolution of a Low-Mass Star
Red Giant & Planetary Nebula 2007-2014 Joseph E. Pesce, Ph.D. = Earth s orbit Not to scale
2007-2014 Joseph E. Pesce, Ph.D.
2007-2014 Joseph E. Pesce, Ph.D.
2007-2014 Joseph E. Pesce, Ph.D.
2007-2014 Joseph E. Pesce, Ph.D.
13-13 High Mass Stars ³5-50 times the mass of the sun ²Last about 1 million years (very short!) ²Create elements through iron (fusion) ² Onion skin ²Expand into Red Supergiant ²Explode as a supernova ²Leave behind neutron stars or black holes
13-14 High Mass Stars ³ Mass high enough after He fusion finishes that compression ignites: ² Carbon (T = 600 million K) ² Neon (T = 1.2 billion K) ² Oxygen (T = 1.5 billion K) ³ Fuses all of these at ever-increasing rates ² For 25 M C - 600 yrs Ne - 1 yr O - 6 months Si - 1 day (at 2.7 billion K)
13-15 High Mass Stars ³ Fusion in shells (onion skin) leads to High L and Large R ³ Supergiants (radius is out to orbit of ~Mars) ³ Fuses through IRON, but iron in core is a problem ² Because iron requires more energy to fuse than it produces ³ Fusion in core stops, core collapses ³ At first, degeneracy holds, but then it exceeds Chandrasekar limit (from shell-fusion ash)
Onion-skin nature of High Mass Stars Outer Atmosphere - Hydrogen Core - Fe Ca Si Ar Ne C Not to scale 2007-2014 Joseph E. Pesce, Ph.D. He
2007-2014 Joseph E. Pesce, Ph.D.
13-18 Type II Supernova ³ Core collapses catastrophically ² 1/10 sec, T~5 billion K ² g-rays tear apart iron atoms ² Neutrinos formed but can t escape tremendous pressures ² Material falling into core bounces back out, burning and blasting everything in it s way ² Extremely high T and densities in the shock wave ² Outer atmosphere blasted, fused, neutrons create elements heavier than iron ² Radioactive decay creates other elements ² Extremely bright (outshining all other stars in galaxy briefly (200 billion) ³ TYPE II supernova
13-19 Type I Supernova ³ Begins as white dwarf ³ If in binary, mass transfer can take place (see binaries above) ³ White dwarf mass exceeds Chandrasekar limit and it explodes ³ TYPE I supernova
Nova ³Non-disruptive explosions of material falling onto a White Dwarf from the accretion disk ³Object brightens for a short time, then fades ³Periodic
2007-2014 Joseph E. Pesce, Ph.D.
Inside the Supernova - 1a Massive Outer Atmosphere Time = 0 sec Core - the size of Earth Orbit of Mars 2007-2014 Joseph E. Pesce, Ph.D. Not to Scale
Inside the Supernova - 1b Massive Outer Atmosphere Time = 0 sec Core - the size of Earth 2007-2014 Joseph E. Pesce, Ph.D. Not to Scale
Inside the Supernova - 2 Massive Outer Atmosphere Time = T+1/4 sec Core collapses Neutron Star forms - 10km; or Black hole! Matter falls in at near light speed 2007-2014 Joseph E. Pesce, Ph.D. Not to Scale
Inside the Supernova - 3 Time = T+1 sec Collapsing material hits central object and bounces Neutron Star forms - 10km; Or Blackhole! High Temperature and Pressure lead to extreme fusion, massive quantities of protons, neutrons, & gamma-rays 2007-2014 Joseph E. Pesce, Ph.D. Matter falls in at near light speed Massive quantities of neutrinos form - try to escape but can t!!!! Not to Scale
Inside the Supernova - 4 Massive Outer Atmosphere Time = T+10 sec Blast wave, propelled by neutrinos and gamma-rays, fuses material as it goes Not to Scale
Inside the Supernova - 5 Time = T+10 min Blast wave continues to destroy stellar atmosphere Neutrinos and gamma-rays finally fly free 2007-2014 Joseph E. Pesce, Ph.D. Not to Scale
The Aftermath - 6 Time = T+1 hour A chaotic, hot environment full of extremely high speed neutrons, protons, and electrons, gamma/xrays, leading to the formation of elements heavier than Iron by neutron bombardment and radioactive decay. Supernova remnant The central object--blackhole or neutron star--heats the remnant and eventually is all that remains of the once-mighty star. The remnant continues to expand and dissipate over the next 10s of thousand years, adding material for the next generation stars. 2007-2014 Joseph E. Pesce, Ph.D. Not to Scale
2007-2014 Joseph E. Pesce, Ph.D.
Supernova: The Animation Time Time = T+1-10,000 > = 10,000 T 0 T+1/4 T+10min sec > 1 sec hour years sec Black hole or neutron star remains 2007-2014 Joseph E. Pesce, Ph.D.
2007-2014 Joseph E. Pesce, Ph.D.
2007-2014 Joseph E. Pesce, Ph.D.
2007-2014 Joseph E. Pesce, Ph.D.
Vela - ~10,000 yrs old
2007-2014 Joseph E. Pesce, Ph.D. The Crab From 1054
2007-2014 Joseph E. Pesce, Ph.D. The Crab From 1054 Chaco Canyon, NM
13-34 End States of Supernovae: Pulsars ³ Collapsed core of high mass star/supernova ³ 10km diameter, extremely high density ³ Some are highly magnetized ³ All spin rapidly ³ Beam of particles squirted from Magnetic axes If toward us, see regular pulses Can be 100s of pulses per second
Rotation axis Magnetic Poles View From Earth: To Earth
13-36 Pulsars in radio: B0329+54: 0.714519s (1.4 rot/sec) Vela: 89ms (11x / sec) Crab: (30x/sec) Youngest 89.3ms = 11/sec B1937+21: (642x/sec) ; rotating 14% c! 2 nd fastest
13-37 Endstates of Supernovae: Blackholes 2007-2014 Joseph E. Pesce, Ph.D.
13-38 Blackholes ³3 times mass of the sun to billions of times ³Small ones among stars in galaxies ³Large ones, apparently at center of every galaxy ³Matter falling in heats up and we see it ³Consumes locally, but has effect on larger scales (jets) ³What goes in can t come out ³Don t know anything about interior (physics doesn t work )
13-39 Evolution of High-Mass Stars
13-40 Importance of High Mass Stars We ARE star stuff!! ³Create all elements though Fe internally ³Create all heavier elements in explosion ³Explode and disperse elements to next generation stars ³Stimulate star formation ³We wouldn t be here but for high mass stars!!
Thank You!