When a Star reaches the end stage of it's life, it runs out of Hydrogen and other elements to fuel it's Fusion reactions. Without the heat pressure to balance out the pull of it's gravity, the core region contracts to an extremely dense state, such as a Neutron Star, or Black Hole. The outer region of the Star sometimes gets blown off in a tremendous explosion called a Supernova, which would outshine all the other Stars in it's Galaxy.
There are 2 general types of supernovas: type 1 and type 2.
Type 1 are white dwarfs that have close-orbiting companion stars that are red giants, and slowly draw their atmosphere onto their surface through tidal interaction. White dwarfs are made mostly of carbon and oxygen, having already depleted their hydrogen and helium, and are kept from collapsing due to electron degeneracy pressure. The red giant's atmosphere, which is mainly hydrogen, accumulates on the surface of the white dwarf. Occasionally it fuses all at once in a chain reaction, creating a nova. However, when enough matter accumulates so that the white dwarf's mass exceeds 1.44 solar masses, the electron degeneracy equilibrium fails and it collapses under gravity. As it collapses, the heat and pressure reach the point where carbon fusion can begin, and the whole white dwarf fuses it's carbon all at once. This destroys the white dwarf star completely.
Type 2 supernovas occur when the core of a large star runs out of nuclear fuel. By this time, the core has fused hydrogen into helium, helium into carbon, that into oxygen, that into neon, that into silicon, and that into iron. Iron is the bottom of the nuclear binding energy curve, which means that no more energy can be achieved by fusing it. The core, by this time, is desperately fighting gravitational collapse by fusing huge amounts of material into heavier ones. Fusion of silicon into iron takes about 2 weeks. When it runs out, the core collapses in less than a second, and reaches the density of an atomic nucleus. This is like bouncing off a brick wall, and the core rebounds and recollapses over and over again. Every collapse produces about 100 million to a trillion degrees K temperature. This is imparted to the rest of the star. The shockwave from the rebounding also is imparted to the rest of the star. The result blows the outer layers of the star to smitherines. The actual energy of a type 2 supernova far exceeds a type 1 supernova, but over 99% of that energy is in the form of neutrinos, which pass harmlessly through matter. The total energy, however, is astounding. It's about as much energy as our sun will produce in 100 times its 10 billion year lifespan, and that in only 10 seconds from an area only 20 miles across.
There is a 3rd type recently discovered, referred to as a pair-instability supernova. That is what is also termed a hypernova, and occurs in stars with huge masses, around 150 or so times the mass of the sun. In those, the core is generating so many gamma rays that it spawns the creation of electron-positron pairs. This stalls the thermal output of the core, and it starts to collapse. As it does, the entire core reaches a temperature where all the nuclear material fuses at once, exploding it. This is one possible source for gamma ray bursts.
Throughout the life of any star there's a struggle going on between its temperature trying to blow it apart and its gravity trying to make it implode (fall in on itself). When a star exhausts its fuel its temperature drops drastically and gravity wins the battle. The outer layers of the star collapse onto its core and a supernova explosion results.
Our sun won't end this way because it takes a star with at least nine times more mass to produce the supernova explosion.
This is only understandable if you know how fusion works, so I'll brake it down a little slowly for you.
Basically a star is made up of gas - Hydrogen gas. It's super hot, and because it's so hot it is constantly "fusing" itself into Helium. This isn't as simple as mixing milk into a coffee, though.
Atoms are made up of three parts, and in hydrogen, they get one of these parts each. One Proton, one Neutron and one electron. Helium (generally) has two of each of these parts.
Generally, if you heat up hydrogen (with no oxygen to 'burn' it) you can't make helium very easily. That's because the atoms of hydrogen are very happy to stay hydrogen. They're perfectly balanced as "one and one and one" and the only way you can say "no! You're getting two of something, and that's that!" is to get it...well as hot as the sun.
But stars are not finite. They only have so much hydrogen (though they've got a TON of it) and eventually, that supply will run out. As the star uses up more and more of it's hydrogen, it expands because instead of having tons of "one and one and one"s running around it gets a huge pile of "two and two and two"s. And the fusion process doesn't end there, either. Eventually, those heliums get turned into other elements which get turned into heavier and heavier things.
The sun puffs up and 'cools' (relatively speaking) as the hydrogen gets used up. (I've heard a theory that the reason that a star expands is due to the hydrogen having more room to move around and collide with other elements and will knock them furhter away because there's no other hydrogens to keep them in place). But just like a bubble when you suck the air out of it, when the hydrogen runs out (or gets low enough), the excitement of the star fades super fast.
This super-fast cooling causes the star to collapse. And there's no where for that matter to go but back to the center of the star. If the process is slow enough you end up with Brown or Red dwarf stars. If it's super fast, you end up with white dwarfs (that are smaller, denser, and manage to restore a strong fusion reaction, though they have less matter to deal with).
But there's a ton of extra energy that gets released from this process. There's lots of extra matter from the star itself that will not head back to the center, but just be released. there's also a ton of matter that will "bounce" from the implosion and explode outwards.
So just like a bubble popping, you end up with a supernova.
Lucky for us, we won't even exist by the time the sun goes supernova.
Answers & Comments
Verified answer
When a Star reaches the end stage of it's life, it runs out of Hydrogen and other elements to fuel it's Fusion reactions. Without the heat pressure to balance out the pull of it's gravity, the core region contracts to an extremely dense state, such as a Neutron Star, or Black Hole. The outer region of the Star sometimes gets blown off in a tremendous explosion called a Supernova, which would outshine all the other Stars in it's Galaxy.
There are 2 general types of supernovas: type 1 and type 2.
Type 1 are white dwarfs that have close-orbiting companion stars that are red giants, and slowly draw their atmosphere onto their surface through tidal interaction. White dwarfs are made mostly of carbon and oxygen, having already depleted their hydrogen and helium, and are kept from collapsing due to electron degeneracy pressure. The red giant's atmosphere, which is mainly hydrogen, accumulates on the surface of the white dwarf. Occasionally it fuses all at once in a chain reaction, creating a nova. However, when enough matter accumulates so that the white dwarf's mass exceeds 1.44 solar masses, the electron degeneracy equilibrium fails and it collapses under gravity. As it collapses, the heat and pressure reach the point where carbon fusion can begin, and the whole white dwarf fuses it's carbon all at once. This destroys the white dwarf star completely.
Type 2 supernovas occur when the core of a large star runs out of nuclear fuel. By this time, the core has fused hydrogen into helium, helium into carbon, that into oxygen, that into neon, that into silicon, and that into iron. Iron is the bottom of the nuclear binding energy curve, which means that no more energy can be achieved by fusing it. The core, by this time, is desperately fighting gravitational collapse by fusing huge amounts of material into heavier ones. Fusion of silicon into iron takes about 2 weeks. When it runs out, the core collapses in less than a second, and reaches the density of an atomic nucleus. This is like bouncing off a brick wall, and the core rebounds and recollapses over and over again. Every collapse produces about 100 million to a trillion degrees K temperature. This is imparted to the rest of the star. The shockwave from the rebounding also is imparted to the rest of the star. The result blows the outer layers of the star to smitherines. The actual energy of a type 2 supernova far exceeds a type 1 supernova, but over 99% of that energy is in the form of neutrinos, which pass harmlessly through matter. The total energy, however, is astounding. It's about as much energy as our sun will produce in 100 times its 10 billion year lifespan, and that in only 10 seconds from an area only 20 miles across.
There is a 3rd type recently discovered, referred to as a pair-instability supernova. That is what is also termed a hypernova, and occurs in stars with huge masses, around 150 or so times the mass of the sun. In those, the core is generating so many gamma rays that it spawns the creation of electron-positron pairs. This stalls the thermal output of the core, and it starts to collapse. As it does, the entire core reaches a temperature where all the nuclear material fuses at once, exploding it. This is one possible source for gamma ray bursts.
Throughout the life of any star there's a struggle going on between its temperature trying to blow it apart and its gravity trying to make it implode (fall in on itself). When a star exhausts its fuel its temperature drops drastically and gravity wins the battle. The outer layers of the star collapse onto its core and a supernova explosion results.
Our sun won't end this way because it takes a star with at least nine times more mass to produce the supernova explosion.
This is only understandable if you know how fusion works, so I'll brake it down a little slowly for you.
Basically a star is made up of gas - Hydrogen gas. It's super hot, and because it's so hot it is constantly "fusing" itself into Helium. This isn't as simple as mixing milk into a coffee, though.
Atoms are made up of three parts, and in hydrogen, they get one of these parts each. One Proton, one Neutron and one electron. Helium (generally) has two of each of these parts.
Generally, if you heat up hydrogen (with no oxygen to 'burn' it) you can't make helium very easily. That's because the atoms of hydrogen are very happy to stay hydrogen. They're perfectly balanced as "one and one and one" and the only way you can say "no! You're getting two of something, and that's that!" is to get it...well as hot as the sun.
But stars are not finite. They only have so much hydrogen (though they've got a TON of it) and eventually, that supply will run out. As the star uses up more and more of it's hydrogen, it expands because instead of having tons of "one and one and one"s running around it gets a huge pile of "two and two and two"s. And the fusion process doesn't end there, either. Eventually, those heliums get turned into other elements which get turned into heavier and heavier things.
The sun puffs up and 'cools' (relatively speaking) as the hydrogen gets used up. (I've heard a theory that the reason that a star expands is due to the hydrogen having more room to move around and collide with other elements and will knock them furhter away because there's no other hydrogens to keep them in place). But just like a bubble when you suck the air out of it, when the hydrogen runs out (or gets low enough), the excitement of the star fades super fast.
This super-fast cooling causes the star to collapse. And there's no where for that matter to go but back to the center of the star. If the process is slow enough you end up with Brown or Red dwarf stars. If it's super fast, you end up with white dwarfs (that are smaller, denser, and manage to restore a strong fusion reaction, though they have less matter to deal with).
But there's a ton of extra energy that gets released from this process. There's lots of extra matter from the star itself that will not head back to the center, but just be released. there's also a ton of matter that will "bounce" from the implosion and explode outwards.
So just like a bubble popping, you end up with a supernova.
Lucky for us, we won't even exist by the time the sun goes supernova.
the answer is actually quite simple just think why a balloon explodes
It's fuel is spent so it collapses and rebounds into a super explosion.