Supernovas?

Question

What's a supernova and how does it happen?

Answer 1

A supernova (pl. supernovae) is a stellar explosion which produces an extremely bright object made of plasma that declines to invisibility over weeks or months. A supernova releases more than about 1017 times the Sun's energy output, briefly outshining its entire host galaxy

Answer 2

In order to supernova, the mass of a dying star must be at least about 1 1/2 times the mass of the sun, known as the Chandrsekar Limit. This figure was calculated by an Indian scientist as the point at which the mass of a dead star would produce such a strong gravitational field that the atoms within the core would be pushed against each other so forcefully that they could no longer remain intact.

Once a dead star cools down, it starts to collapse. Our sun will collapse into what is called a white dwarf. A star that has a core greater than the Chandrsekar Limit but less than about three times the mass of the sun will become a Neutron Star. In this case, the atoms within the core will be forced so close together that the electrons will be forced out of their shells and the neutrons of these atoms will be side by side. The expulsion of the electrons releases a huge amount of energy, causing a supernova.

If the star's core is greater than three times the mass of the sun, it undergoes another, more dramatic collapse. Here, even the forces that keep together the protons and neutrons within the core can't compete with the gravity produced by such a large mass, and the star collapses into a singularity, AKA, a black hole.

The time that a dead star goes from a neutron star to a black hole is, for all intents and purposes, immediate. There isn't any measurable latent period between the two collapses.

As a star supernovas, the outer portions of its shell can't keep up with the collapse of the core. The supernova not only releases a huge amount of energy, but also produces an unimaginably powerful shockwave. As this shockwave strikes the material in portions of the star that didn't shrink with the core, it creates all of the heavier elements that can't be fused within the core of a shining star, and the material is blasted into space.

A supernova is so bright that they easily outshine the galaxy they are in by thousands of times.

Answer 3

Under the Hood :
The solution has come from an unexpected quarter: the physics of car engines. Mixing and igniting gasoline and oxygen in an engine generates turbulence. Turbulence, in turn, increases the surface area of the flames by wrinkling and stretching them. The rate of fuel consumption, proportional to flame area, goes up. A star, too, is naturally turbulent. Because the gas moves vast distances at high velocities, even a slight disturbance quickly turns a smooth flow into a turbulent one. In a supernova, the rising hot bubbles should stir up the material, causing the nuclear burning to spread so fast that the star has no time to compensate.


TYCHO'S SUPERNOVA, a thermonuclear explosion observed by renowned Danish astronomer Tycho Brahe in 1572, left behind a cloud of silicon, iron and other heavy elements glowing in x-rays (green, red). The shock front (thin blue shell) expands outward at 7,500 kilometers a second.
In a properly working internal-combustion engine, the flame propagates at a subsonic speed limited by the rate at which heat diffuses through the material--a process called deflagration. In an engine suffering from knocking, the flame propagates at a supersonic rate, driven by a shock wave passing through the fuel-oxidizer mixture and compressing it--a process known as detonation. Thermonuclear flames can spread in the same two ways. Detonation, being the more violent, would incinerate the star more thoroughly, leaving behind only the most highly fused elements, such as nickel and iron. Observationally, however, astronomers detect a wide variety of elements in these explosions, including silicon, sulfur and calcium. That pattern suggests the nuclear burning propagates, at least initially, as deflagration.
In the past few years, thermonuclear deflagrations have finally been convincingly modeled by our group as well as teams at the University of California, Santa Cruz, and the University of Chicago. The computer code we have honed draws on methods developed for the study of chemical combustion and even of weather. Turbulence is inherently a three-dimensional process. In a turbulent cascade, kinetic energy shifts from large length scales to small ones, where ultimately it dissipates as heat. In other words, the flow becomes ever more finely patterned. Therefore, the simulations have to be three-dimensional, too. That has become feasible only very recently.

Simulating supernovae in their full dimensionality has revealed complex mushroomlike structures--hot bubbles rising in a layered fluid, wrinkled and stretched by turbulence. The increase of the fusion reaction rate wrought by turbulence leads to the disruption of the white dwarf in just a few seconds. The debris expands at about 10,000 kilometers a second, in fair agreement with what the observations show.

Answer 4

A supernova is when a star dyes, it runs out of fuel, implodes and collapses in on itself. Either a neutron star, or black hole (if star was really big) is then instantly formed.