Main Question or Discussion Point
how antigravity force is created before supernova explosion? why it is not created in a body less than chandrashekhar limit?
Below is a good brief description of what goes on in a red supergiant just before supernova-how antigravity force is created before supernova explosion? why it is not created in a body less than chandrashekhar limit?
It really depends on what kind of supernova explosion takes place. In general, supernovae release huge amounts of x-rays and gamma rays, and these could significantly damage the ozone layer in the atmosphere when they reach the Earth. A depletion of the ozone layer could have catastrophic effects for the biosphere, as primary producers would significantly be affected after exposure UV radiation from the Sun, which could lead to a collapse in food webs globally.A Hypothetical question: What would happen to our solar system if there is a supernovae exploding at a distance of our closest star Proxima Centauri at approx 4.2 light years away? What would be the consequences?
The blast from a supernova can be somewhat directional, so the exact consequences for Earth could vary because of that,A Hypothetical question: What would happen to our solar system if there is a supernovae exploding at a distance of our closest star Proxima Centauri at approx 4.2 light years away? What would be the consequences?
The outward force certainly works against gravity, but it is not antigravity in the usual sense of the word. Not anymore than the thrust propelling a rocket away from Earth is antigravity.the outward force that is created during supernova explosion is antigravity force.. at that time gravity collapses.
You were misinformed somewhere. Gravity doesn't "collapse" during the microseconds preceding the supernova event.the outward force that is created during supernova explosion is antigravity force.. at that time gravity collapses.
That Wiki entry promotes some common misconceptions. I knew it would, it's not alone there-- textbooks say similarly misleading things. But it's worth pointing them out to try to set the record straight. For example, the Wiki says "As there is no fusion to further raise the star's temperature to support it against collapse, it is supported only by degeneracy pressure of electrons." This is incorrect, it is never necessary to raise temperature to support against collapse, what you actually need to support against collapse is to maintain the temperature-- you need to replace lost heat. When lost heat is not replaced, what actually happens is temperature rises, so we can see that a constant temperature is a sign of something that is being supported, and a rising temperature is a sign of something that is not being supported. Worse, the Wiki goes on to say "In this state, matter is so dense that further compaction would require electrons to occupy the same energy states."
Note that Ken's referring to the Kelvin-Helmholtz mechanism here. (I think)When lost heat is not replaced, what actually happens is temperature rises, so we can see that a constant temperature is a sign of something that is being supported, and a rising temperature is a sign of something that is not being supported.
That is certainly a standard way to describe the situation, but I am pointing out the potential for that language to lead to misconceptions. In strict terms, the only gross macroscopic effect of degeneracy is the inhibition of heat loss, and as such it does not "cause" an outward force. (It also inhibits internal collisions, so it conducts heat very efficiently, but that just redistributes excess heat, most of the internal kinetic energy is still insulated against any heat loss.)The "outward force" is caused by electron degeneracy. It can resist further compression by the gravity of the star. Bigger stars could overcome even that and create black holes.
The following is an extract from the first link in post #9 which describes what happens just before supernova-the outward force that is created during supernova explosion is antigravity force.. at that time gravity collapses.
As the fusion process continues, the concentration of Fe increases in the core of the star, the core contracts, and the temperature increases again. When the temperature reaches a point where Fe can undergo nuclear reactions, the resulting reactions are different than the ones that have previously taken place. Fe nuclei are the most stable of all atomic nuclei. Because of this, when they undergo nuclear reactions, they don't release energy, but absorb it. Therefore, there is no release of energy to balance the force of gravity. In fact, there is actually a decrease in the internal pressure that works with gravity to make the collapse of the core more intense. In this collapse, the Fe nuclei in the central portion of the core are broken down into alpha particles, protons, and neutrons and are compressed even further. However, they cannot be infinitely compressed. Eventually, the outer layers of material rebound off the compressed core and are thrown outward. This situation can be likened to a rubber ball on the ground that is struck with a hammer. Initially the hammer can compress the rubber ball because of its force, but eventually it is stopped by the density and pressure of the rubber ball reaching its limit, and is thrown back violently by the recoiling rubber ball, which itself will bounce off the surface because of this recoil. In the star, the outer layers of the core are like the hammer, and the core is the rubber ball. Following the collapse of the inner core, the outer layers of the star are pulled toward the center. This sets the stage for a tremendous collision between the recoiling core layers and the collapsing outermost layers. Under the extreme conditions of this collision, two things happen that lead to the formation of the heaviest elements. First, the temperature reaches levels that cannot be attained by even the most massive stars. This gives the nuclei present large kinetic energies, making them very reactive. Second, because of the breaking apart of the iron nuclei in the central core, there is a high concentration of neutrons (called the neutron flux) that are ejected from the core during the supernova. These neutrons are captured by surrounding nuclei, and then decay to a proton by emitting an electron and an antineutrino. Each captured neutron will cause the atomic number of that nucleus to go up by one upon its decay.
That kind of depends on what you mean. If you took a white dwarf, and instantly tagged every electron such that they were no longer indistinguishable and did not obey the Pauli exclusion principle (let's not worry about the impossibility of actually doing that!), you might think that the star would instantly lose its support, and be crushed by gravity, if you think that degeneracy is responsible for the pressure. But this is just the misconception I was alluding to, that isn't true-- the star will still remain quite close to force balance, all that will happen is it will be able to lose heat. So it will start losing heat, and will start contracting, but the contraction will be gradual on the free-fall timescale because the heat transport timescale is still much longer than that. Indeed, over a single free-fall timescale, you might not notice much at all about the white dwarf, when you turn off its degeneracy. I'm not sayinig you claimed otherwise, merely that it is an important clarification to make because we often see language that might be interpreted differently.But gravity is countered, and if not for the degeneracy, it wouldn't be.
I can agree it is macroscopic, but I'm not sure what significance you are implying. It is also quantum mechanical, so we have a granddaddy of an example of a phenomenon that is both macroscopic and quantum mechanical (even better is white dwarfs).And I might assert(insist, demand, have a hissy fit over) that the formation of say, a neutron star is rather macroscopic.