Supernovae

The Crab Nebula is located in the constellation of Taurus. It is about 6,500 light-years away from Earth and is the result of a supernova explosion that was observed in the year 1054.

This is NOT true. Black holes are formed when massive stars explode in supernovas, blowing much of the star into space and crushing the core into a black hole.

One of the things that WILL happen is a massive pulse of x-rays and gamma rays.

There aren't really any comparisons to be made to a supernova. Let's try one; a supernova is as much brighter than the Sun is as the Sun is to a flashlight.

A supernova will release as much energy in an hour as a regular star does in its entire 10-billion year life.

A supernova occurs when a high mass star dies and becomes a neutron star. As the core collapses because fusion burns out and radiation pressure can no longer hold it up, then degenerate electron pressure can not hold it up, the electrons are forced into the nucleus and combine with protons to form neutrons, the strong force causes the nuclei to merge into one ball of neutrons: a neutron star. The surface of the neutron star is very hard and as additional matter from the original star continues to fall in and merge into the neutron star, a "traffic jam" occurs and the shockwave resulting from this reflects off the super hard surface of the neutron star, driving the supernova explosion. Suddenly everything falling in is now rushing out. This can only occur once.

Most stars are dimmer than our sun (intrinsic brightness), and thus we cannot see them. However, most of the stars that we can see are actually quite a bit brighter than our sun. Some of them are exceedingly bright.

Yes and No. White dwarfs generally form from stars that have too low a mass to become supernovae. However, if the white dwarf has a companion star, it is possible for the white dwarf to accrete additional fuel from the neighboring star and then it can explode as a nova {See Link} or a Supernova type La [See link]

Betelgeuse is expected to end its life in a supernova explosion, likely as a Type II supernova due to its massive size and age. This type of supernova occurs when a massive star exhausts its nuclear fuel and collapses under its own gravity.

Unlikely. it has been proposed to explain away the Star. Some stars are unstable and explode in this way with a bright blaze. However, historical records do not indicate a supernova at this time.

Who knows. It may have already happened!!! but because of the distances between stars, we may not know for thousands or millions of years.

Within the Milky Way, possible supernovae are Rho Cassiopeiae, VY Canis Majoris, Betelgeuse, Antares, and Spica. Many Wolf-Rayet stars and those in the Quintuplet Cluster,are also considered possible. The nearest supernova candidate is IK Pegasi (HR 8210), located at a distance of only 150 light years. This closely orbiting binary star system consists of a main sequence star and a white dwarf. The dwarf has an estimated mass equal to 1.15 times that of the Sun. It is thought that several million years will pass before the white dwarf can accrete the critical mass required to become a Type Ia supernova.

Yes and no.

For a nuclear explosion to produce an EMP of enough strength to do damage beyond the range of the blast, thermal flash, prompt radiation, etc. it must occur in the ionosphere, where it can push large amounts of ionized gas large distances through the earth's magnetic field, causing an induced current of billions of amperes in that gas. This EMP can affect an area 1000 miles or more in radius around surface zero. It has been calculated that 3 properly placed nuclear explosions of the right yield in the ionosphere over the continental US would kill the entire US power grid and all solidstate electronics.

Ordinary air or surface bursts do not produce enough EMP for it to even be included in nuclear effects calculations.

No. There are two ways of generating a supernova: a star at least 8 times the mass of the sun collapsing and exploding or a white dwarf interacting or colliding with a companion star. Our sun is not massive enough to explode when it dies and does not have a companion star.

The remnant core of a star that becomes a supernova will normally be a neutron star, or possibly a pulsar (a rapidly spinning neutron star). The largest of stars would theoretically create a black hole, a singularity containing all of the core's mass at a single point and preventing even light from escaping its massive gravity.

Nebula.

Some nebulae are formed as the result of supernova explosions. The material thrown off from the supernova explosion is ionized by the supernova remnant. One of the best examples of this is the Crab Nebula, in Taurus. It is the result of a recorded supernova, SN 1054, in the year 1054 and at the centre of the nebula is a neutron star, created during the explosion.

An excellent question, but without a good answer. Eta Carina is one of the most massive stars that we know of (yet), with a mass upwards of 100 solar masses.

Very massive stars live fast and die young, so we expect it to become a supernova "relatively soon", but "relatively soon" to an astronomer means "Between 10,000 years and 1,000,000 years from now". There is no indication that this event is going to happen within our lifetimes, although at 8,000 light years away, it's possible that we just didn't notice. At that mass, its ultimate fate is most probably to become a black hole.

Depending on the mass of the original star, a supernova explosion may cause a neutron star (for medium to large stars) or a black hole (for large or very large stars). If the original star was rotating fairly rapidly, the neutron star may be a "pulsar", the name given to a rapidly spinning neutron star that emits pulses of X-rays. "Rapidly" spinning in this case is upwards of three revolutions per second.

In a high mass supernova, the outermost layer consists of hydrogen and helium, followed by layers of heavier elements such as carbon, oxygen, silicon, and iron. At the core of the supernova, neutron-rich elements like gold, platinum, and uranium are formed through nucleosynthesis processes during the explosion.

An interesting question and a complicated one to answer. You will have to do some reading and understand the basics of nuclear reactions, to be able to grasp the details. The main difference between stars of the sun's size and larger stars is the temperature of the interior and this makes different reactions predominate. In the sun it is the proton-proton reaction which is most important. In larger stars with higher temperatures a more complicated chain results which includes a carbon-nitrogen-oxygen cycle. In both cases the starting point is nuclei of hydrogen and the end point is nuclei of helium, with energy being released.

You can find out more in Wikipedia entries 'Proton-proton chain reaction' and 'CNO cycle', but be warned, you will have to concentrate hard!

A "pulsar" is a rapidly-rotating neutron star, with a core of collapsed matter. The pulsar rotates because the original star rotated.

If\\ WHEN a massive star becomes a supernova, the force of the explosion will crush the core of the star into either a neutron star or a black hole, if the original star was massive enough. The angular momentum (the "spin energy") of the original star doesn't disappear; like a figure skater pulling in her arms to spin faster, the neutron star will spin more rapidly because it has collapsed in size. If the neutron star's axis is pointed somewhere close to Earth, we detect the pulsating x-rays and we call it a "pulsar".

So to answer the question, all supernova remnants contain either neutron stars or black holes, but they are pulsars only if they spin rapidly.

A Chandrasekhar mass is the maximum mass limit (about 1.4 times the mass of the Sun) that a white dwarf star can have before it collapses under its own gravity and triggers a supernova explosion. When a white dwarf accretes matter from a companion star or merges with another white dwarf, exceeding the Chandrasekhar mass, it can collapse and explode as a Type Ia supernova.

The rapid collapse of the star compresses atoms together and may cause nuclear fusion and make heavier elements.

A supernova is a powerful stellar explosion that occurs at the end of a star's life cycle, leading to a burst of radiation and the creation of heavy elements. A nebula is a vast cloud of gas and dust in space, often formed from the remnants of dying stars or regions where new stars are being born.

about 27 thousand

by Kenny cheung

That is a rediculous answer.

The current Guide Star Catalogue (GSC-II) contains 945,592,683 stars out to magnitude 21. That's almost a billion.

supernovae are classified by the lines in their spectra (which indicate which elements are present). type I supernovae have no hydrogen lines, having been caused by the explosion of a star with no hydrogen envelope. type II supernovae have hydrogen lines, indicating that the exploding progenitor star had retained a significant amount of its hydrogen before its supernova.

type I supernovae are further classified based on the presence of silicon lines, which are present in type Ia supernovae but not types Ib and Ic.

A Supernova explosion will seed the surrounding space with all of the elements created by nuclear fusion in the various layers of the star that preceded the explosion. Nuclear fusion produces less and less energy the heavier the elements used. Once a supergiant star develops a core of Iron and Nickel 56 there is little or no energy being produced by fusion and the star collapses under its own gravitational force causing extreme heat and pressure and then a rebound explosion. This happens in seconds or less. Other products of this supernova are radiation and sub-atomic particles. The heaviest elements produced (Iron and Nickel) accrue neutrons thereby increasing their atomic weight and number and producing heavier and heavier elements. The heavier an element (or metal), the more rare it is. Neutron acquisition can be be either rapid (R-process) or slow (S-process).