| Term | Definition |
|---|
| Type I supernovae | no evidence for hydrogen in spectrum |
| Type II supernovae | definite evidence for hydrogen in spectrum |
| Common elements formed from "building blocks" of helium | carbon, oxygen, neon, magnesium, silicon, calcium |
| Type Ia | brightest, no hydrogen or helium, avoid spiral arms, occur in elliptical galaxies, origin in lower mass stars. Observe silicon early on, iron later. Unregulated burning, explosion in quantum pressure supported carbon/oxygen white dwarf of Chandrasekhar mass. Expected to occur in a in a binary system so white dwarf can grow. Star is completely disrupted, no neutron star or black hole. Light curve shows peak lasting about a week. |
| Type II | explode in spiral arms, never occur in elliptical galaxies, normal hydrogen, massive stars, recently born, short lived. Observe H early on, O, Mg, Ca later. Probably core collapse in iron core of massive star. Light curve often shows month's-long "plateau." Characteristic of explosion in a red giant. |
| Type Ib Supernovae | no hydrogen, but observe helium early on, O, Mg, Ca later. Occur in spiral arms, never in elliptical galaxies. Probably core collapse. |
| Type Ic Supernovae | no hydrogen, little or no helium early on, O, Mg, Ca later. Occur in spiral arms, never in elliptical galaxies. Probably core collapse. |
| Light curves of Type Ib and Ic are similar to Type Ia, | but dimmer at maximum brightness |
| Massive star binaries | Explosions of massive stars in close binary systems are expected to occur in a bare thermal pressure-supported core from which the outer layers of hydrogen have been transferred to the companion star. The core will continue to evolve to iron, in the absence of the hydrogen envelope. This is probably the origin of Types Ib and Ic. |
| To burn a thermonuclear fuel | the star must get hotter to overcome the charge repulsion. This happens automatically in massive stars supported by the thermal pressure that regulates their burning. These stars produce shells of ever-heavier elements and finally a core of iron |
| Iron | (with 26p and 30n) is endothermic, absorbing energy. This will reduce the pressure in the core and cause the collapse of the iron core to form a neutron star. |
| The collapse of the core | gravitational collapse, causes essentially all the protons to be converted to neutrons, releasing a flood of neutrinos and forming a neutron star |
| Repulsive nuclear force between compressed neutrons and neutron quantum pressure | halt the collapse and allow the neutron star to form |
| Neutron star | mass of Sun, but size of a small city. Huge density, surface gravity. Maximum mass of about 2 solar masses |
| Forming a neutron star by core collapse | produces about 100x more energy than needed to create an explosion, but most of that energy is carried off by neutrinos |
| The core collapse explosion of the outer layers of the star may occur in one of three ways: | 1. Prompt mechanism: The neutron star rebounds, driving a shock wave into the outer parts of the star. The bounce shock occurs, but is insufficient to cause an explosion. 2. Delayed mechanism: Neutrinos stirred out by the boiling neutron star deposit heat behind the shock and reinvigorate it. Not clear this is sufficient. 3. Jet mechanism: the collapsing rotating neutron star squeezes the magnetic field and sends a jet up the rotation axis. Naturally makes asymmetric explosion, but not yet clear sufficiently strong jets are produced. |
| Core-collapse structure | Type Ib, Ic, and II, are not spherical.They may be "breadstick" shaped or "bagel" shaped or some combination of elongation and flattening. |
| Jet mechanism | rotation will produce a dynamo amplifying magnetic fields. Computer calculations show that rotation wraps up magnetic field "lines of force" causing the magnetic field and trapped matter to be expelled up (and down) the rotation axis. The generic phrase for this jet mechanism is the "tube of toothpaste effect." |
| Jet-induced explosions | The jets plow up and down along one axis creating a "breadstick" shape and driving bow shocks. The bow shocks propagate away from the jets toward the equator where they collide. The result of this collision is to blow much of the star out along the equator in a torus or "bagel" shape. The final configuration is far from spherical, but has jets in one direction and a torus expanding at right angles to the jet. |
| Jet-induced asymmetry | in addition to producing the jet/torus shape, the jet model predicts that iron is blown along the jet and other elements in the outer layers, O, Mg, Ca, are ejected in the equatorial torus. |
| Failed explosion | if there is no core collapse explosion, outer layers fall in, crush neutron star (maximum mass ~2M) to form a black hole |
| if there is no core collapse explosion, outer layers fall in, crush neutron star (maximum mass ~2M) to form a black hole | must generate explosion in old (1 to 10 billion years) stellar system. Most plausible mechanism mass transfer onto white dwarf |
| Spectra of Type Ia | reveal intermediate elements (O, Mg, Si, S, Ca) on outside and iron-like material on inside. Consistent with models of Chandrasekhar mass carbon-oxygen white dwarfs that begin with a subsonic deflagration and then ignite a supersonic detonation |
| Detonation alone | turn whole white dwarf to iron. |
| Betelgeuse | red giant 427 light years away, 15 to 20M, is expected to explode within 10,000 years, maybe tonight, as core collapse Type II supernova |
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