what causes supernova?????

Question

at the end of its life a star becomes a red giant and blows up
with a stellar explosion called supernova. But where does it get the energy for this supernova. YOU CAN SEND MAILS TO MY ID IF U HAVE SOME PICTUTES OR SOME VALUABLE INFORMATION.

Answer 1

Current models :

Type Ia
There are several means by which a supernova of this type can form, but they share a common underlying mechanism. If a carbon-oxygen[a] 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. However, the current view is that this limit is not normally attained; increasing temperature inside the core ignites carbon fusion as the star approaches the limit, before collapse is initiated. Within a few seconds, a substantial fraction of the matter in the white dwarf undergoes nuclear fusion, releasing enough energy (1–2 × 1044 joules) to unbind the star in a supernova explosion. 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.

One model for the formation of this category of supernova is a close binary star system. The larger of the two stars is the first to evolve off the main sequence, and it expands to form a red giant. The two stars now share a common envelope, causing their mutual orbit to shrink. The giant star then sheds most of its envelope, losing mass until it can no longer continue nuclear fusion. At this point it becomes a white dwarf star, composed primarily of carbon and oxygen. Eventually the secondary star also evolves off the main sequence to form a red giant. Matter from the giant is accreted by the white dwarf, causing the latter to increase in mass.

Another model for the formation of a Type Ia explosion involves the merger of two white dwarf stars, with the combined mass momentarily exceeding the Chandrasekhar limit. A white dwarf could also accrete matter from other types of companions, including a main sequence star (if the orbit is sufficiently close).

Type Ia supernovae follow a characteristic light curve—the graph of luminosity as a function of time—after the explosion. This luminosity is generated by the radioactive decay of nickel-56 through cobalt-56 to iron-56.[31] The peak luminosity of the light curve is consistent across Type Ia supernovae (the vast majority of which are initiated with a uniform mass via the accretion mechanism), allowing them to be used as a secondary standard candle to measure the distance to their host galaxies.

Type Ib and Ic
These events, like supernovae of Type II, are probably massive stars running out of fuel at their centers; however, the progenitors of Types Ib and Ic have lost most of their outer (hydrogen) envelopes due to strong stellar winds or else from interaction with a companion. Type Ib supernovae are thought to be the result of the collapse of a massive Wolf-Rayet star. There is some evidence that a few percent of the Type Ic supernovae may be the progenitors of gamma ray bursts (GRB), though it is also believed that any hydrogen-stripped, Type Ib or Ic supernova could be a GRB, dependent upon the geometry of the explosion.

Type II
The onion-like layers of a massive, evolved star just prior to core collapse. (Not to scale.)Stars with at least nine solar masses of material evolve in a complex fashion. In the core of the star, hydrogen is fused into helium, releasing the energy needed to support the overlaying layers against collapse (see hydrostatic equilibrium). Once the core's supply of hydrogen is exhausted, the core contracts until the temperature and pressure rise high enough to allow helium fusion. As the star evolves, it undergoes repeated stages where fusion in the core stops, and the core collapses until conditions allow ignition of the next stage of fusion, temporarily halting further collapse.

Fusion of lighter elements continues to occur in shells surrounding the core at radii where the required conditions and fuel are found. These stars become layered like onions, with the burning of more easily fused elements occurring in larger shells. The outermost shell fuses hydrogen to create helium, which is fused to create carbon in the next lower shell, and so forth.

As increasingly heavier elements undergo nuclear fusion, the binding energy of the nuclei increases and progressively lower levels of energy are produced. This culminates with the production of nickel-56, which does not produce energy through fusion (but does produce iron-56 through radioactive decay). As a result, a nickel-iron core builds up that can only support the overlaying mass of the star through the degeneracy pressure of electrons. When the core's size exceeds the Chandrasekhar limit, degeneracy pressure can no longer support it and a catastrophic collapse ensues.

Core collapse
The core implodes at velocities reaching 70,000 km/s (0.23c), resulting in a rapid increase in temperature and density. Through photodisintegration, gamma rays decompose the iron into helium nuclei and free neutrons. The conditions also cause electrons and protons to merge through electron capture, producing neutrons and electron neutrinos. About 1046 joules of gravitational energy are converted into a ten-second burst of neutrinos. These carry away energy from the core and accelerate the collapse, while some neutrinos are absorbed by the star's outer layers and begin the supernova explosion.

The inner core eventually reaches a density comparable to that of an atomic nucleus, where the collapse is halted. The infalling matter then rebounds, producing a shock wave that propagates outward. Computer simulations indicate that this expanding shock will stall in the outer core as energy is lost through the dissociation of heavy elements, and that a process that is not clearly understood is necessary to allow the shock to reabsorb 1044 joules[b] (1 foe) of energy, producing an explosion.


Within a massive, evolved star (a) the onion-layered shells of elements undergo fusion, forming an iron core (b) that reaches Chandrasekhar-mass and starts to collapse. The inner part of the core is compressed into neutrons (c), causing infalling material to bounce (d) and form an outward-propagating shock front (red). The shock starts to stall (e), but it is re-invigorated by neutrino interaction. The surrounding material is blasted away (f), leaving only a degenerate remnant.
When the progenitor star is below about 20 solar masses (depending on the strength of the explosion and the amount of material that falls back), the degenerate remnant of a core collapse is a neutron star. Above this mass the remnant collapses to form a black hole. (This type of collapse is one of many candidate explanations for gamma ray bursts—producing a large burst of gamma rays through a still theoretical hypernova explosion.) The theoretical limiting mass for this type of core collapse scenario was estimated around 40–50 solar masses.

Above 50 solar masses, stars were believed to collapse directly into a black hole without forming a supernova explosion,[50] although uncertainties in models of supernova collapse make accurate calculation of these limits difficult. In fact recent evidence has shown stars in the range of about 140–250 solar masses, with a relatively low proportion of elements more massive than helium, may be capable of forming pair-instability supernovae without leaving behind a black hole remnant. This rare type of supernova is formed by an alternate mechanism (partially analogous to that of Type Ia explosions) that does not require an iron core. An example is the Type II supernova SN 2006gy, with an estimated 150 solar masses, that demonstrated the explosion of such a massive star differed fundamentally from previous theoretical predictions.

Light curves and unusual spectra

This graph of the luminosity (relative to the Sun) as a function of time shows the characteristic shapes of the light curves for a Type II-L and II-P supernova.The light curves for Type II supernovae are distinguished by the presence of hydrogen Balmer absorption lines in the spectra. These light curves have an average decay rate of 0.008 magnitudes per day; much lower than the decay rate for Type I supernovae. Type II are sub-divided into two classes, depending on whether there is a plateau in their light curve (Type II-P) or a linear decay rate (Type II-L). The net decay rate is higher at 0.012 magnitudes per day for Type II-L compared to 0.0075 magnitudes per day for Type II-P. The difference in the shape of the light curves is believed to be caused, in the case of Type II-L supernovae, by the expulsion of most of the hydrogen envelope of the progenitor star.

The plateau phase in Type II-P supernovae is due to a change in the opacity of the exterior layer. The shock wave ionizes the hydrogen in the outer envelope, which greatly increases the opacity. This prevents photons from the inner parts of the explosion from escaping. Once the hydrogen cools sufficiently to recombine, the outer layer becomes transparent.

Of the Type II supernovae with unusual features in their spectra, Type IIn supernovae may be produced by the interaction of the ejecta with circumstellar material. Type IIb supernovae are likely massive stars which have lost most, but not all, of their hydrogen envelopes through tidal ********* by a companion star. As the ejecta of a Type IIb expands, the hydrogen layer quickly becomes optically thin and reveals the deeper layers.

Answer 2

Well, any supernova that was close enough to cause large numbers of animal die-offs would certainly be detectable by other means, and we'd see an incredibly brilliant light in the sky. Since neither of those things have happened, I think we can rule out a supernova. The 2012 hoax junk is no more plausible than it was before. The vast majority of the hoax bits are simply not possible without ignoring basic laws of physics and orbital mechanics. I did a search for "Russian Pole movement"--nothing on yahoo or google news. Doing a straight google search for the phrase returned zero hits. That's pretty hard to do with a search for three common words. If you can find a link, it would be an interesting read. Yes, the cause of many previous mass-deaths is known. But they're only known because eventually someone figured out a cause, and that can take time. We haven't reached "eventually" yet.

Answer 3

The facts stated as part of your question are not entirely correct. While most stars go through some type of giant phase throughout their life time, only stars exceeding a certain mass will end up as super novas.
The energy comes when the star runs out of nuclear fuel and collapses when gravity takes over and the star implodes. It is during this supernova stage that the star attains temperatures high enough to produce all the heavy elements that it cannot produce during it's normal lifetime. The resultant explosion scatters this material into space where, under the right conditions it can condense and form New Stars and planets like our solar system. It is these supernova remnants that contain all the heavy elements necessary for life. We are literally made from Star Dust.

Adolph

Answer 4

A black hole is produced when a very massive star runs out of fuel. When the energy of fusion stops, the explosive energy keeping the star "inflated" at it's present size ends, and there's nothing but it's immense gravity acting on it's mass. The star collapses, creating a super-dense mass, and a massive explosion - blowing OUT huge amounts of matter, while at the same time, compressing an extremely massive core.

What happens to the core is based on the mass of the star and the force of the explosion. If the core is compressed such that the electrons and protons of it's atoms are merged, you end up with a mass made up of nothing but neutrons - a neutron star. Usually, these spin very rapidly (The Crab Nebula is the end result of a supernova, with a neutron star rotating at about 30 times a second.)

If the force of the explosion and mass is even more powerful, collapse doesn't stop there - it compresses the core down to a dimensionless point in space - a black hole. Surrounding this black hole, is the Event Horizon - a border between the realm of a black hole - where escape velocity is greater than the speed of light, and normal space.

Answer 5

At the end of its life a star becomes a red giant but it does not blow up with a stellar explosion called supernova in the process. A super nova is completely different as described by sb above. The change of a normal star to a red giant star happens rather more slowly and sedately.

Answer 6

From -http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernovae.html <--- this site also contains an image =D

"For Type II supernovae, mass flows into the core by the continued making of iron from nuclear fusion. Once the core has gained so much mass that it cannot withstand its own weight, the core implodes. This implosion can usually be brought to a halt by neutrons, the only things in nature that can stop such a gravitational collapse. Even neutrons sometimes fail depending on the mass of the star's core. When the collapse is abruptly stopped by the neutrons, matter bounces off the hard iron core, thus turning the implosion into an explosion: ka-BOOM!!!

For Type Ia supernova, the energy comes from the run-away fusion of carbon and oxygen in the core of the white dwarf."

P.S. Gravity is the one giving a supernova energy

Answer 7

I think in some suitable conditions the Sun became Supernova and after that the supernova becomes a star or a black hole.

Answer 8

Supernova is how hot a star can get so at the end of its life it would explode as a result of over heating.

Answer 9

when stars became old

Answer 10

http://homepage.mac.com/mrlaurie/btcfolder/astro2002webpages/Period%202/suernova.html

Answer 11

WHen the stars die..