What is a supernova? Does it have to do with a red giant or a super giant?

Question

Is a ring formed as gases are pushed away?
Are Gases and dust packed very tightly together?

Answer 1

A star starts out fusing hydrogen atoms into helium. Once it runs out of hydrogen, it starts fusing the helium. At this point, the star begins to enlarge since the inert helium core has no source of energy of its own, it contracts and heats up, and its gravity compresses the hydrogen in the layer immediately above it, thus causing it to fuse faster. This in turn causes the star to become more luminous (from 1,000 to 10,000 times brighter) and expand, becoming a Red Giant.

At some point, if the star has enough mass, it will begin to fuse the helium into carbon, and continues making heaveir and heavier elements until it hits iron. The iron nucleus is the most tightly bound, and fusing it into heavier stuff takes energy that the star doesn't have.

At this point, supernova occurs when the star in question cannot generate enough pressure from the core because it can't fuse the iron atoms, and it begins to collapse due to gravity. As the collapse begins, it starts to compress the atoms once again, and with a violent explosion, the supernova, the star fuses some of the iron into the heavier elements. This shock wave sends out the dust and debris in a massive explosion that we sometimes see as an illuminated ring of dust, and the pressure wave can cause other stars to form.

Answer 2

A supernova is the explosion of a massive star. A star powers itself through nuclear fusion. First, hydrogen is fused into helium. Then, if the star is massive enough, heavier nuclei are also fused. Eventually, if the star is over 1.4 solar masses, the remaining matter cannot be fused to generate heat and light, so the star collapses in on itself. This results in a burst of uncontrolled fusion where heavy nuclei are created and the outer layers of the star are thrown away violently. Generally, a nebula is formed; it is possible for a nebula to have the general shape of a ring or disk.

For an excerpt from my reference, see the answer below mine.

Answer 3

A supernova (plural: supernovae or supernovas) is a stellar explosion that creates an extremely luminous object. A supernova causes a burst of radiation that may briefly outshine its entire host galaxy before fading from view over several weeks or months. During this short interval, a supernova can radiate as much energy as the Sun would emit over 10 billion years. The explosion expels much or all of a star's material at a velocity of up to a tenth the speed of light, driving a shock wave into the surrounding interstellar medium. This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant.

Several types of supernovae exist that may be triggered in one of two ways, involving either turning off or suddenly turning on the production of energy through nuclear fusion. After the core of an aging massive star ceases to generate energy from nuclear fusion, it may undergo sudden gravitational collapse into a neutron star or black hole, releasing gravitational potential energy that heats and expels the star's outer layers. Alternatively, a white dwarf star may accumulate sufficient material from a stellar companion (usually through accretion, rarely via a merger) to raise its core temperature enough to ignite carbon fusion, at which point it undergoes runaway nuclear fusion, completely disrupting it. Stellar cores whose furnaces have permanently gone out collapse when their masses exceed the Chandrasekhar limit, while accreting white dwarfs ignite as they approach this limit (roughly 1.38 times the mass of the Sun). White dwarfs are also subject to a different, much smaller type of thermonuclear explosion fueled by hydrogen on their surfaces called a nova. Solitary stars with a mass below approximately nine solar masses, such as the Sun itself, evolve into white dwarfs without ever becoming supernovae.

On average, a supernova occurs about once every 50 years in a galaxy the size of the Milky Way and play a significant role in enriching the interstellar medium with heavy elements. Furthermore, the expanding shock waves from supernova explosions can trigger the formation of new stars.