What force is created before supernova explosion?

[Subrata Paul]

how antigravity force is created before supernova explosion? why it is not created in a body less than chandrashekhar limit?

 

[wabbit]

What do you mean by "antigravity force" ?

 

[caters]

I think he means an outward force so big that the whole star expands.And in that case it is produced in every single star in the universe other than brown and red dwarfs(brown and red dwarfs just gradually die off like how a battery gradually dies off so no outward force other than the one produced by fusion is involved) from small ones like our sun that will never supernova to large ones like betelgeuse that will definitely supernova within the next 10,000 years.

 

[wabbit]

Ah you lost me here, what is this outward force you are referring to ?

Also, do you have a reference to the fact that Betelgeuse will go supernova in the next 10,000 years ? This seems extremely precise, I wonder how we can get such accuracy ?

 

[caters]

This outward force that I am referring to is the pressure produced by the star's core to counteract gravity which always trys to shrink the star. When you have a massive star(more massive than our sun) at some point pressure is greater than gravity so the star expands. Before that though some stars will actually shrink right before helium fusion starts. This is a helium flash. Then after years of being a red giant or supergiant(and in rare cases hypergiant(hypergiants are the biggest stars in the universe)) the pressure gets so big that while the core contracts due to gravity forming a neutron star or if the star is supermassive, a black hole the outer layers continue to expand at a rapid pace. This is a type II supernova

 

[wabbit]

OK I see - pressure is nothing one would call antigravity, but also, as I understand it this is not what causes a supernova explosion. On the contrary, if I recall correctly, it is insufficient pressure to counteract gravity that provokes a collapse, and the explosion is the resulting rebound. Describing this as antigravity seems very weird, if anything the force causing the explosion is gravity.

Regarding Betelgeuse, I found this article, which is reporting on http://arxiv.org/abs/1406.3143 : Evolutionary tracks for Betelgeuse (Michelle M. Dolan, Grant J. Mathews, Doan Duc Lam, Nguyen Quynh Lan, Gregory J. Herczeg, David S. P. Dearborn). They estimate ~100k years, which seems quite precise already. Very interesting stuff.

 

[Vanadium 50]

Roughly 20x as much writing has been expended guessing what the OP means. Why not wait for him to explain what he means?

 

[Chronos]

The outward force in a supernova is created by matter recoiling from the degenerate core during collapse. There are also significant neutrino emissions involved as well - no antigravity required.

 

[stevebd1]

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-
http://aether.lbl.gov/www/tour/elements/stellar/stellar_a.html

I suppose you could say that it is the mass of the original star that results in there being a supernova or not. A star with an original mass of up to 8 sol will result in a white dwarf, a star with an original mass of between 8 and 18 sol will result in a supernova & neutron star, and a star with an original mass of more than 18 sol will result in a supernova & black hole.

source-
http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit3/extreme.html

 

[harshith_cs]

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?

 

[PWiz]

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?

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.
I'm not 100% sure, but IMO the radiation should affect human satellites near Earth as well.

 

[rootone]

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,
However even if Earth were located well away from the regions of maximum blast, I'm pretty sure that the amount of gamma radiation received from a supernova that close to Earth would likely sterilize all life, and probably fry the atmosphere into a highly ionized state.

 

[Subrata Paul]

What do you mean by "antigravity force" ?

the outward force that is created during supernova explosion is antigravity force.. at that time gravity collapses.

 

[Drakkith]

the outward force that is created during supernova explosion is antigravity force.. at that time gravity collapses.

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.

 

[Chronos]

The general consensus among scientists is the minimum safe distance for a supernova is in the range of 50-100 light years as noted here - http://Earth'sky.org/space/supernove-distance.

 

[SteamKing]

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.

If anything, once fusion stops in the core of the star, gravity is able to cause the core to compress to a tiny fraction of its original size, since there is nothing, no force, which counteracts it.

You should read something about supernova formation, to get the correct idea about the sequence of events:

http://en.wikipedia.org/wiki/Type_II_supernova

 

[Ken G]

http://en.wikipedia.org/wiki/Type_II_supernova

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."
That's also incorrect, further compaction is certainly possible if sufficient work is supplied, degeneracy never prevents collapse any differently from any other kind of pressure, it simply sets the requirements for collapse like any pressure does. Degeneracy pressure is, in that sense, a completely mundane type of pressure, and a natural aspect of pressure is that work is required to produce compaction. But like with any nonrelativistic gas pressure, the work that would be supplied to produce compaction causes an increase in pressure which exceeds the increase in gravity, this is normal gas-pressure stability no different from an ideal gas. So it bounces back-- gravity does not contract gas pressure supported objects unless there is net heat loss. So what neutron degeneracy really does, which has no direct connection with producing pressure, is to eliminate further heat loss, and gravity always requires heat loss in order to obtain further contraction. Degeneracy is a thermodynamic effect that inhibits heat loss, not a mechanical effect that produces pressure.

 

[Drakkith]

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.

Note that Ken's referring to the Kelvin-Helmholtz mechanism here. (I think)

 

[Ken G]

Right. That mechanism says that if there is net heat loss, gravity will slightly exceed pressure. It is a misconception to say that the heat loss ever causes temperature drop, however-- the temperature can rise monotonically everywhere, throughout the process. The key is that the slight excess of gravity is always causing contraction, allowing gravity to do work that pumps kinetic energy into the system-- usually at a rate twice as large as the net heat loss that is driving the whole business. Thus the excess kinetic energy piles up and causes the continuing temperature rise, but even though the temperature is steadily rising, the rising gravity continues to slightly exceed the pressure.

Anything that short-circuits the net heat loss will stop this process, and either fusion or degeneracy can do that-- fusion by replacing lost heat, degeneracy by preventing heat loss in the first place.

 

[AgentSmith]

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.

 

[Ken G]

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.

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.)

Admittedly, what constitutes a "cause" is not necessarily cut-and-dried in science, but let me offer this analogy. Take a hot ball of self-gravitating ideal gas, say a protostar, prior to any fusion. Now surround it with a big mirror, so no heat can escape. That protostar will quickly cease contracting. Would we say that the mirror is causing the outward force in that star, that prevents it from collapsing? The role of degeneracy in a white dwarf or neutron star is quite similar to that mirror-- it is the reason there is no further contraction, but it is not the cause of the outward force. The cause of the outward force is the internal kinetic energy of the particles, and nothing else.

So what happens in bigger stars? The neutrons go relativistic. It turns out that relativistic kinetic energy is never good at producing pressure that can resist gravitational contraction, because then gravitational contraction only supplies an equal amount of energy as needed for the increasing pressure to keep pace with the increasing gravity (so continues to lag behind if out of balance), rather than providing twice that amount as happens in nonrelativistic gas (so causes the pressure to eventually rise up and exceed gravity, as happens in a core bounce). That fact has nothing to do with degeneracy, degeneracy only tells you if heat loss will be stopped before the gas goes relativistic. If the gas has already gone relativistic, degeneracy is of no importance.

 

[stevebd1]

the outward force that is created during supernova explosion is antigravity force.. at that time gravity collapses.

The following is an extract from the first link in post #9 which describes what happens just before supernova-

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.

 

[Ken G]

And note that excellent entry is still quite vague about the reason for this "limit" that the core reaches. The standard but incorrect answer is that the limit is some new kind of pressure that appears when the gas goes degenerate. Actually, "degeneracy pressure" is a perfectly mundane form of gas pressure, its arrival merely signifies a situation where the gas (now a gas of free neutrons) can no longer lose heat and thus goes adiabatic, and if it is nonrelativistic, adiabatic compression always causes this mundane gas pressure to rise faster than the gravity does. The "limit" is thus a limit on how much heat can be lost from the core, which is only indirectly a limit on the force scale. But if the neutrons go relativistic, they are not stabilized against compression even in the adiabatic limit, so that's what leads to black hole formation.

 

[AgentSmith]

[ QUOTE="Ken G, post: 5139168, member: 116697"]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.)

(snipped paragraph).

So what happens in bigger stars? The neutrons go relativistic. It turns out that relativistic kinetic energy is never good at producing pressure that can resist gravitational contraction, because then gravitational contraction only supplies an equal amount of energy as needed for the increasing pressure to keep pace with the increasing gravity (so continues to lag behind if out of balance), rather than providing twice that amount as happens in nonrelativistic gas (so causes the pressure to eventually rise up and exceed gravity, as happens in a core bounce). That fact has nothing to do with degeneracy, degeneracy only tells you if heat loss will be stopped before the gas goes relativistic. If the gas has already gone relativistic, degeneracy is of no importance.[/QUOTE]

Well, your are correct. Thats why I left outward force in quotes, though. But gravity is countered, and if not for the degeneracy, it wouldn't be. And I might assert(insist, demand, have a hissy fit over) that the formation of say, a neutron star is rather macroscopic.

 

[Ken G]

But gravity is countered, and if not for the degeneracy, it wouldn't be.

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.

And I might assert(insist, demand, have a hissy fit over) that the formation of say, a neutron star is rather macroscopic.

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).

 

[phyzguy]

The general consensus among scientists is the minimum safe distance for a supernova is in the range of 50-100 light years as noted here - http://Earth'sky.org/space/supernove-distance.

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.
I'm not 100% sure, but IMO the radiation should affect human satellites near Earth as well.

The blast from a supernova can be somewhat directional, so the exact consequences for Earth could vary because of that,
However even if Earth were located well away from the regions of maximum blast, I'm pretty sure that the amount of gamma radiation received from a supernova that close to Earth would likely sterilize all life, and probably fry the atmosphere into a highly ionized state.

Chronos, PWiz, and rootone have all claimed that a supernova at the distance of 4.3 light-years would be catastrophic for life on Earth. I'd like to examine how you came to this conclusion. I discount the link Chronos posted, since it is full of obvious errors. First, it confuses years and light-years, an elementary mistake. Second, it states that, if the sun were to go supernova, the side of the Earth facing the sun would be boiled away. This is silly; since supernova explosions last for weeks, all of the Earth's surface would be impacted. Third, it states that, "The sudden decrease in the sun’s mass might free the planet to wander off into space." This is also nonsense. So ignore that article. What are the facts? A typical supernova has an absolute magnitude of about -18, and this luminosity lasts for a few weeks. At a distance of 4.3 light years, this would be an apparent magnitude of about -27.5, as compared to the sun at -26.7. So the Earth would have a second sun for a couple of weeks. This would clearly wreak havoc with the weather, but it wouldn't be a sterilizing event, and I think we would clearly survive. As far as X-ray and Gamma-ray emission, the articles I could find indicate that these emissions are far less than the emission of visible light. We are not talking a gamma ray burst, which would clearly be catastrophic at this distance if it were pointed at us, but an ordinary supernova. Gamma ray bursts are very rare events, and the odds of one happening nearby are extremely small. All of this is a long-winded way of asking whether anyone can back up the statement that a supernova 4.3 light-years away would be a sterilizing event.

 

[PWiz]

Chronos, PWiz, and rootone have all claimed that a supernova at the distance of 4.3 light-years would be catastrophic for life on Earth. I'd like to examine how you came to this conclusion. I discount the link Chronos posted, since it is full of obvious errors. First, it confuses years and light-years, an elementary mistake. Second, it states that, if the sun were to go supernova, the side of the Earth facing the sun would be boiled away. This is silly; since supernova explosions last for weeks, all of the Earth's surface would be impacted. Third, it states that, "The sudden decrease in the sun’s mass might free the planet to wander off into space." This is also nonsense. So ignore that article. What are the facts? A typical supernova has an absolute magnitude of about -18, and this luminosity lasts for a few weeks. At a distance of 4.3 light years, this would be an apparent magnitude of about -27.5, as compared to the sun at -26.7. So the Earth would have a second sun for a couple of weeks. This would clearly wreak havoc with the weather, but it wouldn't be a sterilizing event, and I think we would clearly survive. As far as X-ray and Gamma-ray emission, the articles I could find indicate that these emissions are far less than the emission of visible light. We are not talking a gamma ray burst, which would clearly be catastrophic at this distance if it were pointed at us, but an ordinary supernova. Gamma ray bursts are very rare events, and the odds of one happening nearby are extremely small. All of this is a long-winded way of asking whether anyone can back up the statement that a supernova 4.3 light-years away would be a sterilizing event.

I stated that the effects are dependent on the type of supernova explosion.

Here is a paper where the chances of a mass extinction caused by a supernova near Earth are discussed:
http://arxiv.org/abs/hep-ph/9303206

Here is link to NASA's website where assertions about the effects of a near Earth supernova are made:
http://www.nasa.gov/topics/earth/features/2012-supernova.html

Although a supernova releases fewer gamma rays than a GRB, the amount released is still significant to greatly damage the Earth's atmosphere and biosphere at a distance less than 50 light years from Earth. (Again, the effects are dependent on the type of supernova explosion that occurs)

 

[Chronos]

The most authoritative study is probably that by Gehrels, et al - http://arxiv.org/abs/astro-ph/0211361, Ozone Depletion from Nearby Supernovae - which puts the minimum safe distance from Earth at about 8 parsecs for a core collapse supernove. But, that distance cannot be trusted as sate for the more dangerous type 1a supernova, as noted by Phil Plait here http://blogs.discovermagazine.com/b...the-closest-supernova-candidate/#.VYUt4vlViko. It is usually good policy to favor citations over subjective judgments in matters of science.

 

[phyzguy]

Chronos and PWiz,
Thanks for providing these references. Reading through them, it appears to me that a nearby supernova could cause a significant impact on the Earth's ozone layer, which could significantly damage the biosphere and lead to extinctions. I don't find any evidence, however, for rootone's claim that "the amount of gamma radiation received from a supernova that close to Earth would likely sterilize all life." This is what I was taking issue with. While a supernova at the distance of Alpha Centauri would be bad, it doesn't appear that it would be a sterilizing event.

 

[rootone]

Well OK, the gamma radiation might be survivable by organisms living below the Earth's surface, but the consequences for the atmosphere and the biosphere at surface level would be seriously damaging.
A massive extinction is highly probable, and the possibility of complete annihilation of surface living organisms can't be discounted.
Exposure to intense gamma radiation is no fun at all.

 

[harshith_cs]

Thanks a lot everyone for the research! :)

 

[K. Doc Holiday]

I have to agree with rootone. Professor Neil F. Comins in his book "Discovering the Universe" seventh edition, page 375 says;

"Considering the titanic forces supernovae release, it should come as no surprise that the high-energy electromagnetic radiation from such an explosion detonating much closer than this distance [50 light years] would immediately kill virtually all life on earth."

Next: the sun will never be a candidate for a core collapse supernova. A star must be greater than 3 Solar Masses to undergo a core collapse. When the sun expands to a red giant (this probably won't occur for 5 billion years) then it will swallow the 3 inner planets (that includes earth) completely. When it collapses to a white dwarf after throwing off its outer layers it becomes a candidate for a type 1a supernova, in theory. Since the sun is in the minority amongst stars and as such has no companion star(s) then it cannot steal mass from that companion which is required for a type 1a supernova. Conclusion: the sun will never supernova. If it did, we would be wiped out in less than 9 minutes, about the time it would take light and gamma rays to reach earth.

Next: the closest candidate for a core collapse event is Betelgeuse. It is hundreds of light years away (about 650 ly ) It would light up the sky and be visible during the day but it would not adversely affect life on earth. The consensus amongst Scientists is the closest candidate for a type 1a supernova is IK Pegasi which is about 150 light years from earth. [a core collapse event is uneven as it explodes. A type 1a is the complete destruction of a white dwarf from the inside and as such is virtually uniform.] A supernova 150 light years from Earth would significantly damage the ozone layer and kill life forms sensitive to ultraviolet radiation. The most damage would occur because of the Electromagnetic pulse (EMP) that would accompany the gamma rays.

It is uncertain how powerful the EMP from a supernova this close would be but it might be enough to shut down any unprotected electronic devices. Cars in motion would lose power and crash. Any airplane with a stall speed greater than 100mph would crash. It might fry all the active satellites in orbit around earth. The Earth would protect those shielded on the opposite side of our planet from the gamma rays but an EMP is in wave form and would circumvent the planet. There would be millions of lives lost and trillions of dollars.

The up side is nature gives us a warning in the form of a neutrino burst that precedes all supernova. Supernova 1987a was 168,000 light years away. The neutrino detectors on Earth picked up a burst of neutrinos about 12 hours before we saw the light from the blast. (neutrinos are so weakly interacting with matter that they manage to escape the blast before the gamma rays and light of the explosion.) Even 2 hours of warning would be enough to avert the worst damage provided we had emergency protocol in place.

Gamma Ray Bursts occur in the early formation of a galaxy (nature of the beast). The Milky Way has long ago past the point where our galaxy will host such an event.

p.s. Contrary to the consensus of the scientific and academic communities I think AN Ursae Majoris is the closest candidate for a type 1a (standard candle) supernova. At a distance of 124 light years it would be imperative to have protocol in place before the blast wave hits us. If our neutrino detectors light up like Christmas trees the protocol should automatically go into effect. Of course, i could be wrong but why take chances? We have nothing to lose and everything to gain by establishing protocols.

 

[nikkkom]

At a distance of 4.3 light years, this would be an apparent magnitude of about -27.5, as compared to the sun at -26.7. So the Earth would have a second sun for a couple of weeks. This would clearly wreak havoc with the weather, but it wouldn't be a sterilizing event, and I think we would clearly survive.

That is more like three Suns.

Venus insolation is "only" 190% of Earth's.

Having 3x insolation for weeks would cause air temperature to quickly rise well above 100 Celsius.

Looks sterilizing to me.

 

[K. Doc Holiday]

I have been informed that all our discussions have to accept current theories as gospel truth and we cannot mention anything other than that gospel, even if that gospel clearly violates the laws of logic and common sense. I didn't realize that when i joined this forum. I wish all of you the best! I am out of here. :)

 

[Drakkith]

I have been informed that all our discussions have to accept current theories as gospel truth and we cannot mention anything other than that gospel, even if that gospel clearly violates the laws of logic and common sense. I didn't realize that when i joined this forum. I wish all of you the best! I am out of here. :)

Well, the problem is that human logic and common sense are fallible. That's why empirical science exists. Besides, we recognize that all of science has the potential to be improved or even overturned by new findings. Nothing is accepted as an absolute truth. However, PF exists to teach people about mainstream science, which means that discussions must be centered around what science currently understands, whether or not it seems to violate common sense.