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Why a stars collapses when iron is the only element left in the core?
TansuTukhvatulina
When hydrogen fuses into helium, extra energy is released, causing more fusion. When helium fuses into carbon, extra energy is released, causing the reaction to continue. When each element fuses into heavier ones, energy is released - until you get to iron.
When iron fuses into heavier elements, or when anything fuses into elements heavier than iron, it sucks energy OUT of the reaction, slowing it down. This is like poison to a nuclear reaction; sucking the energy OUT of a star rather than releasing it. The star dies instantly, and the collapse causes a titanic explosion in which even MORE energy is sucked out of the core of the star, as heavy elements fuse into heavier ones, until the heavy elements like Uranium and thorium are so massive that they cannot hold together and begin to fall apart.
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The above answer isn't exactly right. An over simplification.
Normal stars, like our sun, live just long enough to begin fusing helium into carbon. At that stage, they generate so much energy that they essentially boil off their outer layers, in a stellar nova. Eventually they boil off everything but their inner carbon core, leaving a white dwarf. But giant stars, like Betelgeuse, have enough mass to hold together. This mass, and the immense force at the stars core, provides enough energy to fuse carbon into heavier elements.
Nuclear fusion is not easy. So far we have only achieved it through a two step reaction, beginning with a nuclear fission explosion. You have to put energy in to get energy out. The reason is the electromagnetic charge of the atomic nucleus. The nucleus is made of positively charged protons and neutrally charged neutrons. It takes a lot of force to overcome these charges. The bigger the nucleus, the more force required to fuse it.
So, after fusing all of its available helium into carbon, the star is on borrowed time. Each stage in the star's fusion cycle is shorter than the last, simply due to the availability of the fuel. After billions of years of fusing hydrogen, millions of fusing helium, time quickly runs short. Carbon fusion last about 600-1000 years. Carbon fusion produces neon, neon fusion lasts roughly 1 year. Next is oxygen fusion, lasting maybe 6 months, producing silicon. But then, something strange happens. In every previous step of the fusion cycle, fusion produces more energy than it consumes, but iron is the other way around. Silicon fusion produces iron, but iron fusion requires too much energy, effective ending all nuclear fusion at the core. Silicon fusion lasts 3-5 days, and at that time there is not enough energy left in the core to fuse anything, and the core collapses under the weight of the stars mass. This collapse goes until protons an neutrons are crushed together so tight the the entire mass becomes pure neutrons. This stops the collapse momentarily, sending enormous shock waves through the stars outer layers, causing massive runaway nuclear reactions, blasting the star apart in a type II super nova. The runaway nuclear reactions produce elements heavier than iron through neutron accumulation. At the core, one of two things happens: Either the nuclear forces stop the collapse, forming a neutron star, or the force of the collapse overpowers the nuclear forces, and the core collapses into a black hole.
On a related note, the star Betelgeuse, mentioned earlier, is a red super giant, and is believed to be rapidly supernova. In fact, given its distance of over 800 light years away, it is likely that it already has gone supernova. When it does, or rather when the supernova's light reaches earth, it will outshine even the full moon in the night sky, and be easily visible in broad daylight. The supernova will last about 6 mouths, before fading away for good. It should produce a neutron star.
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The above statement "Nuclear fusion is not easy. So far we have only achieved it through a two step reaction, beginning with a nuclear fission explosion." is not completely true, referring to the "so fare we have only" part. We have achieved cold fusion by using super conducting magnets to drive hydrogen particles into each other. They reach speeds near light speed, then clash into each other. If the collision is direct enough they will fuse into helium. This produces far more energy than the energy used to crash them into each other. Once we find a way to harvest that energy we can create cold fusion reactors.
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Well, just a small addition. Fusion has been accomplished with lasers also. Work at the National Ignition Facility Lawrence Livermore Laboratories, has produced small fusion reactions and they hope to create a sustained reaction at some point.
Wiki User
∙ 10y ago
Wiki User
∙ 14y agoFusion of heavier and heavier elements requires greater and greater density to start. Over time a star runs out of lighter elements as it fuses them into heavier ones. However if the star is not massive enough it will not be able to achieve the density necessary to fuse the heavier elements. Other forces besides fusion counteract the gravity trying to collapse the star dense enough to start fusion of heavier elements.
Wiki User
∙ 13y agoAn active star is a balance between the outward force of the energy released by fusion in its cor and the inward force of gravity. For most of its life a star fuses hydrogen into helium. When the star runs out of hydrogen in its core it starts fusing heavier elements, but fusing these produces less energy.
Eventually the star gets to iron. Fusing iron actually takes energy rather than releasing it. At this point there is no longer any outward force to counteract gravity and the star essentially crushes itself.
Wiki User
∙ 13y agoBasically when there is no more fuel - when all, or most of, the lighter elements are used up.
Wiki User
∙ 13y agoIt explodes within a matter of Seconds! Iron absorbs the energy created in the fusion cycle.
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What do blue super-giant and red or yellow dwarf stars evolve into?
The endgame for any star depends upon its mass. Blue stars, typically class O, are very massive, and will eventually nova (supermassive stars that nova with exceptional violence are termed supernovas, again, a function of the star's mass) after all or most of the hydrogen has been fused into helium. A large chunk of mass is blown off during the nova stage, and the star collapses. The collapse heats the core and triggers the fusion of helium. This can continue a considerable number of times, until the star is actually forming iron. All elements above iron on the periodic table can be be fused with themselves to form the next element in an exothermic reaction, meaning it generates energy in addition to the new element. Iron fused to iron is endothermic, it takes more energy to make it fuse than the fusion produces. The final nova will then see the core collapse yet again, but without a new fusion reaction to stop the collapse, the core will collapse to for "degenerate matter", a neutron star, or potentially a quasar. Extremely massive stars may, theoretically, form black holes instead, as the core collapse is so violent even neutron star matter cannot withstand the pressure, and the entire mass of the star is collapsed down to a single point. Dwarf stars are, of course, far less massive. When they use up their hydrogen, they swell into a red giant, then collapse back down. Low mass stars may retain too little mass to start the next fusion cycle, and will become a white dwarf. Larger stars may be able to stand a few cycles of new fusion, but soon will not retain enough mass to start another, and also shrink to white dwarf stars. Over time, the white dwarf stars will cool and become brown dwarf stars. A sun the size of Sol would expand enough as a red giant to very near Earth's orbit, which will be very bad news for anyone here in a few billion more years.
How do stars more massive than four solar masses evolve into neutron stars?
I've seen that figure of 4 times the Sun's mass, but the usual number given is at least 8 times the Sun's mass. Anyway here's the answer: The general idea is that, depending on how much mass is left once the star runs out of fuel, it may become a white dwarf, a neutron star, or a black hole. A star like the Sun goes through a "red giant" star stage then becomes white dwarf star. Stars that are much more massive than the Sun go through a "supergiant" stage. They finally run out of fuel. The core of the star is now mainly iron. If, after running out of fuel, the amount of mass left in the core is more than a certain limit - the Chandrasekhar limit, currently believed to be about 1.39 times the mass of the Sun - the core's "electron degeneracy" pressure is not enough to resist the gravitational force on the core. In this case, the core of the star collapses into a neutron star or black hole and causes a supernova explosion.
What is the definition of a core in electrical equipment?
A core in the electrical trade usually refers to the iron laminations that coils of wire are wrapped around. The core directs the magnetic field, that the coils of wire produce when energized, into a working force. This could be the iron core of a relay or a transformer core that is the centre and principle reason that a transformer can operate.
A slogan for iron?
i run for iron. iron is not a metalloid its a awsomeoid. iron is steel. iron is the strongest element if u just believe.
Why is iron the heaviest element that can be produced by star?
It isn't; heavier elements can be, and are, produced by DYING stars. The reason is the "packing fraction curve". As atomic nuclei would fuse together within the cores of normal stars, hydrogen atoms as "fuel" would fuse into helium "ash"; when the star became old, the core of the stars would heat up and become more dense as the star began to collapse into itself. The denser stellar core material would heat up and begin to fuse into heavier elements; carbon, oxygen, and heavier elements, releasing a little energy every time a new atom was formed by fusing together lighter ones - UNTIL they got to iron. Once you get to iron, any additional fusion sucks energy OUT of the star's core, and every fusion from there on sucks even MORE energy out of the star, leading to the star's quick collapse. This is one scenario for how a "nova" might occur. If a star EXPLODES in a supernova, then there's LOTS of energy to crash even heavy elements together into even HEAVIER elements. So all of the gold, uranium, lead, and every atom heavier than iron, was formed in a supernova explosion.
How do stars get blasted off?
an expanding Shell of hydrogen gas envelop the core of the star which collapses ,it becomes a red giant. In more massive star with hotter core ,helium fuses to carbon,silicon or oxygen, synthesizing the heavier element .even more massive stars may burns iron generating a cooling effect . The core implodls and the outer layer of the stars are bloom away as a supernova
What is the number of proton in the element iron?
In the element iron there are 26 protons. In the core there are 30 neutrons as well, and 26 electrons are circling around this core.
Which element makes up a large percentage of Earths core and a much smaller percentage of the crust?
The principle element found at the Earth's core is iron.
The most abundant element in the Earth's inner core and outer core is?
Iron.
What element makes up most earth core?
The element that makes up most of the earths CORE is iron.
The final core element for a massive star is?
IRON
Why do stars cool when the fusion cycle gets to iron?
Unlike lighter elements, fusing iron consumes more energy than it produces. This does not, however, cause a star to cool. Once a star gets to the point of fusing iron, the core stops producing energy and without the pressure from the heat it produces, the core collapses while the rest of the star is blasted away in an explosion.
What element blows a supernova up?
Supernovas, other than Type Ia are initiated when too much iron builds up in a star's core. Fusing iron and heavier elements absorbs energy rather than releasing it. Once the core reaches the point that it no longer produces energy it collapses, causing the star around it to explode.
What element makes up most of the core?
Iron and nickel
What element largely makes up earths core?
iron
What elements are in iron?
Iron is an element. It has an atomic number of 26, and by mass, it's the most common element that makes up the Earth ... a large part of Earth's core is iron. Iron is the only element in pure iron.
What element makes up most of earth's core?
Refer to complete article at http://en.wikipedia.org/wiki/Inner_core
