What force is created before supernova explosion?

  • #26
phyzguy
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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://earthsky.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.
 
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  • #27
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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)
 
  • #28
Chronos
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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.
 
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  • #29
phyzguy
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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.
 
  • #30
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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.
 
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  • #31
Thanks a lot everyone for the research! :)
 
  • #32
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.
 
  • #33
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.
 
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  • #34
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. :)
 
  • #35
Drakkith
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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.
 
  • #36
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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.

.....

(It [EDM] 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.)

So, how does EDM prevent heat loss if it is a thermal conductor?
 
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  • #37
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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.
I agree that it would kill off most of the humans. A tripling of the incoming radiation would mean a rise in the absolute tempererature of the 4th root of 3, so 288k * 1.316 = 379K, so about 106C. This is of course a calculation only based on the Stefan-Boltzman radiation law, and ignores such things as water vapour/cloud formation, wind patterns etc. Three weeks of 3 times solar radiation is however less than what the sun does to warm the oceans in a summer, so the oceans should warm less than 10 degrees C from this. You might survive if you live near the ocean.
Moreover, you'd survive near one of the poles, and likely a large part of the northern or southern hemisphere wouldn't get much extra radiation.
Where I live at 53 N, december insolation is only about 13% of summer insolation. If the sun became 3 times as bright, for a few weeks in winter, that would be no problem at all.
 
  • #38
I agree that it would kill off most of the humans. A tripling of the incoming radiation would mean a rise in the absolute tempererature of the 4th root of 3, so 288k * 1.316 = 379K, so about 106C.
Venus is only x1.9, yet its surface temp is in excess of 450 C!

Evidently, your model is grossly oversimplified.
 
  • #39
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Venus is only x1.9, yet its surface temp is in excess of 450 C!

Evidently, your model is grossly oversimplified.
But Venus didn't get like that in a few weeks.

You have a maximum of 700 W/m^2 extra coming in. (no clouds, no reflection, ignoring the extra outgoing radiation as the surface heats up).
In a month this is 4.34 * 10^10 J/m^2. Enough to evaporate 20 meters of water, or heat 100 meters of water by 45 degrees or a combination of both, but not nearly enough to sterilize the earth, and a part of the earth will escape, no matter where the supernova is.
 
  • #40
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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.
Not true, gamma ray burst come from the collapse of supermassive stars.

When a huge star's core collapses, it creates a black hole in the middle of it. When that happens, the inside of the star quickly starts hollowing out as the black hole swallows it from the inside. The intense gravity creates an accretion disc inside the star and near the event horizon particles are accelerated to nearly the speed of light in a column perpendicular to the spinning disc. Those jets are the gamma ray burst.

WR 104 is a potential gamma ray burst waiting to happen, and it's also pointed right at us.
 
  • #41
Ken G
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So, how does EDM prevent heat loss if it is a thermal conductor?
It is a perfect conductor with no heat to lose, like a superconductor at absolute zero. Exactly like that, in the limit of complete degeneracy.
 

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