supernovae

Supernovae- Stellar explosion

can outshine an entire galaxy before dimming within several weeks or months. radiate as much energy as the sun does in its entire lifespan Expels much of stars at 1/10 of the speed of light shockwave causes a supernova remnant, an expanding shell of gas and dust can be caused by star turning off or nuclear fusion begining. large stars may turn into black holes or neutron stars white dwarfs have novas, much smaller thermonuclear explosion

occur every fifty years in milky way

play a significant role in enriching the interstellar medium with higher mass elements. CRUCIAL to stellar evolution. Big bang only created helium, hydrogen, and lithium. All other elements created in supernovae.

//supernova// was first used in print in 1926 and was coined by Swiss astrophysicist and astronomer, Fritz Zwicky

Type 1a If a carbon-oxygen white dwarf accreted enough matter to reach the Chandrasekhar limit of about 1.38 solar masses (for a non-rotating star), it would no longer be able to support the bulk of its plasma through electron degeneracy pressure and would begin to collapse. An outwardly expanding [|shock wave] is generated, with matter reaching velocities on the order of 5,000–20,000 [|km/s], or roughly 3% of the speed of light. There is also a significant increase in luminosity, reaching an [|absolute magnitude] of -19.3 (or 5 billion times brighter than the Sun), with little variation.

Type 1b and 1c From larger stars Types Ib and Ic have lost most of their outer (hydrogen) envelopes due to strong [|stellar winds] or else from interaction with a companion 1c may be progenators of gamma ray bursts

Type 2 In the core of the star, hydrogen is fused into helium and the [|thermal energy] released creates an outward pressure, which maintains the core in [|hydrostatic equilibrium] and prevents collapse. When the core's supply of hydrogen is exhausted, this outward pressure is no longer created. The core begins to [|collapse], causing a rise in temperature and pressure which becomes great enough to ignite the helium and start a helium-to-[|carbon] fusion cycle, creating sufficient outward pressure to halt the collapse. The core expands and cools slightly, with a hydrogen-fusion outer layer, and a hotter, higher pressure, helium-fusion center

If the star is sufficiently large, then the iron-nickel core will eventually exceed the [|Chandrasekhar limit] (1.38 [|solar masses]), at which point this mechanism catastrophically fails

the newly formed neutron core has an initial temperature of about 100 billion [|kelvin] (100 GK); 6000 times the temperature of the sun's core