well, i'm just kinda confused that how these reactions take place on sun as well as other stars. i'll appreciate the help thanks Please Register or Log in to view the hidden image!
Stars are very hot. The reactants (e.g. hydrogen nuclei) buzz around very fast and slam into each other. If they have enough energy, they can fuse together to form heavier elements (like helium). When that happens, energy is released, which helps maintain the temperature of the star.
WELL they are supposed to take place after nuclear fusion(if temp is effective), isnt it?Please Register or Log in to view the hidden image!
plus i'd like to know how he will eventually form the heavy metals? will he atons will fuse together again?
In chemistry, when chemicals react, they first need to gain energy, so they can climb an activation energy hill. Once at the top of this hill they can slide down the other side of the hill and give off energy. The new chemical state is stable since to reverse it, we would need add energy to make it climb the hill in the other direction before it can fully change. Please Register or Log in to view the hidden image! Although harder to measure for nucleosynthesis, an analogous activation energy hill also need to be climbed. You can't just take deuterium in a jar and expect fusion. It will never climb the activation energy hill under those conditions. In terms of H-bombs, we don't need gravity to create fusion, since the activation energy can be done directly within energy. Gravity may help get the ball rolling in stars, but once lit, you don't even need gravity, just the output from the seeds atoms sliding down the other side of the hill. If you took a curve of the energy release due to fusion as a function of atomic size, the smaller atoms tend to give off more energy than larger atoms. This is useful since the smaller atoms can provide the activation energy for the larger atoms, so they can climb their hill easier. In the image above, the activation hill is actually for atoms larger than iron, which absorb energy when they form. They still need to climb the activation energy hill, but end in a state higher in energy than they started.
[You should proofread.] During the lifetime of stars fusion reactions take place leading to the formation of elements up to iron. Heavier elements are formed during supernova explosions.
The process of hydrogen fusing to form helium involves a number of intermediate steps. One of those involves the formation of deuterium, as you say.
Since the earth is about 4.5 billion years old while the universe is 13.7 billion, one can safely assume there was at least one generation of stars before the earth was formed.
The Sun is actually a third generation star. As for nuclear fusion, there are several pathways that the Sun takes. Our Sun mostly uses the proton-proton chain. It is a series of several steps that takes 4 hydrogen nuclei and fuses them into helium. Basically, two protons fuse together to make deuterium, than another proton fuses with it to create "light helium" (2 protons 1 neutron), and this light helium fuses with another light helium to produce regular helium (2 protons 2 neutrons) and two separate protons (hydrogen nuclei), with each step producing a few energy particles like positrons and neutrinos along the way. This is only possible in the Sun because of its very large temperature in the core. Temperature is a measure of the average kinetic energy in a system, or the energy of motion. With a high temperature the atoms in the Sun swarm incredibly fast, by chance some of the atoms ram into each other and because of the high energies they posses from moving so fast they fuse together when they smash into each other. If they don't have enough energy or don't hit each other in the right way fusion will not occur. Other, more massive, stars use other pathways like the CNO cycle that takes carbon and changes it through adding in various protons and those new atoms partially decaying ending with carbon12 which is the start of the cycle. Our Sun uses the CNO cycle a little bit, but not a lot, most of the energy comes from the proton-proton chain. There are other pathways of nuclear fusion, but those are the most basic. It is all dependent on temperature, which in turn is determined by mass for main-sequence stars like the Sun.
Mathman is correct re:"formation of "pre-Fe" pre-nova and "post-Fe post-nova elements. We are all "made of pre-nova and post-nova star-stuff!!" . . . but there is other "stuff" from whence all this evolved . . . .
With what is said above and what Mathman has said, "During the lifetime of stars fusion reactions take place leading to the formation of elements up to iron. Heavier elements are formed during supernova explosions" both give the basic knowledge required.Please Register or Log in to view the hidden image!
so is it possible anyway that the meteors whose major component is iron, were once stars, and they formed out of a stellar nucleosynthesis?
There are a lot of unknowns when it comes to things like this, but in my view meteors are improperly formed planetary leftovers. But you are right the material they came from originally was a Star explosion.Please Register or Log in to view the hidden image!
