Some Dead Stars May Harbor Enough Uranium To Set Off a Thermonuclear Bomb (sciencemag.org) 96
sciencehabit shares a report from Science Magazine: A thermonuclear bomb might be ticking deep in the cores of some dead stars. A new theoretical study traces out how certain stellar corpses known as white dwarfs could accumulate a critical mass of uranium that would trigger a massive supernova explosion.
The findings could yield insights into the destruction habits of white dwarfs, which are responsible for creating heavy elements like iron and nickel. White dwarf supernovae light up their surroundings with the power of 5 billion Suns, and astronomers have used them as 'standard candles' to measure vast distances across the cosmos. But such blasts are still not entirely understood, and the new study could account for certain, anomalously dim observations of this type of supernovae. The findings appeared on the preprint server arXiv this month and have been accepted for publication in Physical Review Letters.
The findings could yield insights into the destruction habits of white dwarfs, which are responsible for creating heavy elements like iron and nickel. White dwarf supernovae light up their surroundings with the power of 5 billion Suns, and astronomers have used them as 'standard candles' to measure vast distances across the cosmos. But such blasts are still not entirely understood, and the new study could account for certain, anomalously dim observations of this type of supernovae. The findings appeared on the preprint server arXiv this month and have been accepted for publication in Physical Review Letters.
Distraction (Score:5, Funny)
These stories make you think about all these far away stars that don't affect us but the terrifying truth is that the Sun - which is right next to us - has enough hydrogen for the equivalent of multiple H-bomb explosions per second for billions of years. It's also pretty much accepted fact that the Sun will one day destroy the Earth. But the people in power don't want to do anything about it because they're dependent on the Sun for their vast fortunes.
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This is pretty much why megacorps want to own our water (and sell a lot of sunscreen while at it).
They don't want to give us the power to tame the Sun.
Re: Distraction (Score:2)
Re: Distraction (Score:5, Informative)
Re: Distraction (Score:5, Interesting)
They sink to the centre but as they sink, they get hotter than the non radioactive elements and rise. Not to mention gravitational weirdness at the core. When you are on the surface of a planet, the entire mass of the planet pull you down, when you are at the centre of a planet, half the mass of the planet pulls one way and the other half pulls the other, you are in a low gravity, high pressure, high temperature environment, likely all sorts of intense close in electromagnetic field flows. The bigger the mass the greater the weirdness going on down there.
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>"... half the mass of the planet pulls one way and the other half pulls the other, you are in a low gravity, high pressure, high temperature environment, likely all sorts of intense close in electromagnetic field flows."
That is interesting, and spooky, considering that all of this is going on beneath our feet right now.
Re: Distraction (Score:5, Interesting)
A parasitic effect that absorbs energy created by the fusion reaction without contributing to it.
I would imagine that this does not happen on a large scale inside stars, so only small quantities of these heavy elements are produced during the star's life time. But once the star enters the white dwarf phase and heavy elements accumulate at the centre, in theory it should be possible that enough fissile material accumulates to reach critical mass.
Of course just hypotheses on my side.
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Re: Distraction (Score:5, Interesting)
That's when the nuclear binding energy "breaks even". Beyond that point fusion becomes endothermic. That means it requires more energy to add more protons to a nucleus than is released in the process.
In theory, this ought to be possible during the normal lifetime of a star, when now and then some more protons are added to the nucleus of an iron atom.
Just think about it. What would happen to an iron nucleus that gets hit with more protons at such energies?
Though from the lifetime of stars we can guess that this would happen rather rarely, because if this was a common phenomenon stars would 'burn out' a lot faster. I would also assume that the likelihood for such an endothermic fusion to happen to decrease with the mass of the element in question. Something as heavy as uranium, which contains 92 protons (compared to 26 in iron and 28 in nickel), should be quite rare.
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As you move beyond iron in the periodic table, atomic nuclei become less stable and are prone to splitting - i.e. undergoing fission. This is why elements such as uranium an
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In theory, this ought to be possible during the normal lifetime of a star, when now and then some more protons are added to the nucleus of an iron atom.
My understanding is that this cannot happen.
The star sits in an equilibrium where there is enough energy to fuse what it's fusing at the time, and nothing heavier. Only further collapse can increase the energy.
The electron degeneracy pressure is too much for it to fuse heavier than iron, without going supernova.
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Not really. Fusion of elements heavier than iron is endothermic, so a star can only derive energy by fusion of lighter elements, but that's just the dominant reaction. There can and will be less common fusions of heavier elements.
But stars are big, so even a very uncommon reaction fusing elements into uranium can produce an assload of uranium.
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It's my understanding that there simply isn't enough energy. If there *is* enough energy (gravitational energy) that star's fate is sealed- it's not going to end as a "dead star" (white dwarf that didn't have the gravitational energy to go supernova).
Do you have any good articles or papers I could read that would support your assertion?
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I don't have any papers on it, just the knowledge that given a bunch of iron atoms and particles flying around, occasionally one or more will be captured. It's not the dominant reaction, it's just part of the noise. Evidently it's not a novel idea since TFA seems to assume it will happen.
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It assumes no such thing. It assumes uranium exists within stars for the same reason it exists within plants- because it's heavy, and supernovas blast it all around the universe.
As I mentioned, it's understood that a star doesn't have enough energy to fuse iron. The energy for the fusion reactions comes from the gravitational energy.
At the point where there would be enough gravitational energy to fuse iron, you run up against the electron degeneracy pressure, an
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You're still thinking in bulk. Remember, the energy of individual atoms of anything at any temperature follows a bell curve. There will always be very high energy outliers. Hydrogen fusion can happen at room temperature and pressure, just exceedingly rarely and to no significant effect.
A neutron star doesn't really have elements other than a thin layer over the neutronium core.
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Remember, the energy of individual atoms of anything at any temperature follows a bell curve.
This is untrue.
The products of a fusion reaction have very specific energies.
Hydrogen fusion can happen at room temperature and pressure, just exceedingly rarely and to no significant effect.
No, it can't.
That's a gross misuse of "room temperature"
By that you can only mean an experiment that is surrounded by room temperature, but the temperature of the individual atoms is of course not at that.
A neutron star doesn't really have elements other than a thin layer over the neutronium core.
Correct. Which is why the processes only happen when a material is accreting onto a neutron star. i.e., regular atoms landing on a surface where the gravitational energy is more than the electron degeneracy pressure.
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The products of a fusion reaction have very specific energies.
And then they have a million of so non-fusion interactions and spread out into a nice bell curve.
That's a gross misuse of "room temperature"
Not at all. Fill a container with hydrogen at room temperature. The energy of individual molecules will fall into a bell curve. There will be only a small but existing chance that some of them will have sufficient energy to fuse. Wait long enough or get a big enough container and a fusion WILL happen. You probably won't detect it and the temperature increase in the container will be lost in the noise, but it wil
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And then they have a million of so non-fusion interactions and spread out into a nice bell curve.
No, they do not follow a normal distribution.
The claim is patently false.
There may be situations where it is true, but it cannot be true in the general sense.
Not at all. Fill a container with hydrogen at room temperature. The energy of individual molecules will fall into a bell curve.
Beyond being wrong (a bell curve is a normal distribution. What you are referring to is a Maxwell-Boltzmann distribution) it simply isn't relevant.
The Coulomb barrier for fusion of anything past Nickel-56 (which is unstable and will decay into Iron-54) cannot be breached by anything in the Silicon Burning process of stars, which itself only exists f
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There will be only a small but existing chance that some of them will have sufficient energy to fuse.
No. This is patently false.
This is cold fusion, and it does not happen.
A single molecule can be instantaneously raised to the level of passing a hydrogen atoms coulomb barrier pretty easily, but this is not room temperature fusion. The molecule that breached it had the required energy. As I said, you are misusing the term.
I.e., a flame does not cause any spontaneous fusion, because the Maxwell-Boltzmann distribution simply doesn't allow for it.
Now, if you could put the entire energy of a flame into a s
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I'm not expert in solar nuclear physics, but I do have some education in it, and this was taught to me as an impossibility (under current theory)
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I haven't done the math myself for the 'proton stuff'. All I can tell you is that there is an energy barrier -- the Coulomb barrier for fusion to happen.
The more protons you have in the nucleus the larger the positive charge of the nucleus is and the more energy you need for another proton or entire other nuclei to penetrate t
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Please read till the end in the future. Sometimes from that you can already guess whether the commenter might know a paper supporting it or not.
That's completely fair.
I missed that.
I haven't done the math myself for the 'proton stuff'. All I can tell you is that there is an energy barrier -- the Coulomb barrier for fusion to happen. The more protons you have in the nucleus the larger the positive charge of the nucleus is and the more energy you need for another proton or entire other nuclei to penetrate that barrier and to be added to the core. So that's what is required, enough energy to be present to overcome that barrier. If those energies are given during the various fusion stages within a star I cannot tell you.
Yes. In an argument with someone else on this thread who was directly asserting what you are hypothesizing, I have done the relevant research, and the fact is: No. It's quite impossible to fuse into uranium in normal stellar fusion.
There simply isn't enough energy.
Since in a star, the energy of the fusion reaction is in equilibrium with the pressure caused by the gravitational collapse, we know the exact breaking limit of fusion within it, prior to core collapse.
As i
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One man is willing to stand up.
https://youtu.be/L3LbxDZRgA4?t... [youtu.be]
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Re:Distraction (Score:5, Informative)
And, in this case, "multiple" is on the order off 100 billion H-bombs per second. Assuming a MT-range H-bomb. If you want to talk in terms of Hiroshima-type booms, multiply by 100 or so....
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Mr. Burns - Since the dawn of time man has yearned to destroy the sun.
Re: Distraction (Score:2)
Presumably by the time the Sun explodes, cockroaches would have evolved to be the most intelligent species on the planet and will think of a way to get us out of that mess.
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Sounds impressive (Score:5, Insightful)
Until you remember that a live star is essentially a huge continuous fusion bomb only held in check by massive gravity and fusion explosions are a lot more impressive than fission ones and a fission supernova would probably be a bit meh compared to a "normal" one.
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By definition a bomb is something that releases its stored energy in a sudden burst.
Also I'd argue that it's not massive gravity that keeps it in check, I'd say that it is massive gravity that keeps the reaction going.
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Sudden is relative to your attention span.
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Much like the oxidation that powers us is "sudden".
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It doesn't mean much indeed. The point about fission would be noteworthy if it was not already covered in the article;
"..the new study could account for certain, anomalously dim observations of this type of supernovae.."
Most people react to the summary.
Re: Sounds impressive (Score:3)
Re:Sounds impressive (Score:5, Informative)
We estimate that the solids may be so enriched in actinides that they could support a fission chain reaction. This reaction could ignite carbon burning and lead to the explosion of an isolated WD in a thermonuclear supernova (SN Ia).
So it seems that the fission reaction could trigger a much larger thermonuclear(fusion) supernova, I don't think there could be a fission supernova but fission can trigger a fusion reaction.
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Which, incidentally, is exactly how a hydrogen bomb works - a smaller fission device goes bang and the released radiation compresses and heats the hydrogen fuel present sufficient to spark fusion, which then creates even more heat and compression...
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FWIW our bog standard little firecracker thermonuclear bombs on earth ( vs the scale we're talking) are ALSO triggered by fission explosions to start.
What I'm not sure about (and shan't take the time to deep-delve and figure it out) is why, in particular, they feel that outcome is likely possible? Stellar processes tend to stop at Iron 56, or really Calcium 40, anyway far far short of the transuranium area of the periodic table. Elements up there are the RESULT of supernovas or (more recent theory) the im
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The uranium comes from the same place as here, a previous supernova or neutron star merger. Once the star stops fusing, the heavier elements settle towards the middle and may reach critical mass/density, fission and trigger carbon fusion leading to a weak supernova compared to the usual types.
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D'oh...
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Except a white dwarf is a dead star where most of the fusion has shut down. I didn't read the paper, but it seems likely that if you somehow managed to get enough fissile material in the same place in the core it would produce a lot of neutrons, which would reignite fusion in the core of the star, which could produce the boom. Just like in a hydrogen bomb.
A star is not a bomb (Score:1)
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Semantics - its exactly the same reaction. If you stuck an H bomb at the centre of the sun you'd see no difference.
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Semantics - its exactly the same reaction.
Not really. The reaction in an H bomb is typically Lithium-6 + Deuterium => Helium-4 + neutrons. (We'll skip over the fact that in most bombs, this reaction is mainly used to generate neutrons to drive fast fission of large quantities of U238, which actually generates most of the yield.)
The main reaction in the sun is a slow, complex catalyzed process with a net result of 4*Hydrogen-1 => Helium-4
If you stuck an H bomb at the centre of the sun you'd see no difference.
You certainly could see a difference if you had a sensitive enough neutrino detector.
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Slow in comparison to what , plank time? The energy may take decades to get from the centre but the reactions happen in nanoseconds.
But I guess you didn't have time to crib that from google.
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What's your point? I simply pointed out that it's a different reaction with different fuel and different products. Not "It's exactly the same reaction". I also pointed out that you could detect the different products, not "You'd see no difference".
People also don't generally care about how long each particle takes to react vs. the overall *reaction rate*. That's why if they pull you over and find a bunch of C4 explosives in your car, their concern is about those explosives and not the fact that your car is
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Slow in comparison to what , plank time? The energy may take decades to get from the centre but the reactions happen in nanoseconds.
The reaction is ongoing.
There is no appreciable single event, unless we try to divide it up into the individual atoms fusing.
You're picking at increasingly tenuous straws to support a point that was stupid from the outset. Stop it.
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Where did I say it wasn't ongoing?
"unless we try to divide it up into the individual atoms fusing."
Yes, thats the fucking point! What did you think I meant, there was 1 big fusion reaction at the suns birth and that was it?? Moron.
The number of people on slashdot who can't even comprehend basic english is very worrying.
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Until you remember that a live star is essentially a huge continuous fusion bomb only held in check by massive gravity and fusion explosions are a lot more impressive than fission ones and a fission supernova would probably be a bit meh compared to a "normal" one.
This statement is stupid.
A star isn't a "continuous fusion bomb" any more than a fission reactor is a "constant fission bomb"
The distinction between a bomb and a reactor is whether or not the reaction is stable, or runaway.
In the sun, it is not runaway, so it is not a bomb.
There is no prompt explosion, as I said, unless we take each and every fusion as a single event.
Now I'm not going to resort to calling you a moron, but your ability to construct meanin
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A star is a fusion reactor.
A fission reactor is not a bomb- it's a stable reaction.
That fact that it uses the same dynamics isn't relevant.
That's like saying a match is essentially a bunker buster.
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Until you remember that a live star is essentially a huge continuous fusion bomb
Struggling with the difference between "bomb" and "reactor?" (-- don;t like the quotes outside the question mark but it's what I was taught - brain doesn't like it, tho)
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One of the more interesting statistics that I have seen was that, even given the very high density in the core of the Sun, the average energy release per unit volume was about the same as a well tended compost heap...
a new theory (Score:1)
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Also said by physicists to Einstein in 1905. Time is an important concept.
Re: a new theory (Score:2)
Also said to flat earthers. Just because Einstein had criticism of his theories, doesnâ(TM)t mean every crackpots theory is equally valid as Einstein.
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You can't prove a theory, or hypothesis, only disprove it. If you can't disprove it, then it is more likely correct or close to correct but just like gravity, still a theory.
We know (Score:2)
"Some Dead Stars May Harbor Enough Uranium To Set Off a Thermonuclear Bomb "
We all saw the guy starring as predator in 'The Predator' explode.
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That was a methane explosion!. That actor had pork and beans for lunch the day they filmed that scene.
Okay.... but.... (Score:3)
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So kinda like some of those 50's experiments where the blast was larger than anticipated because some expected to be nonreactive isotopes transmuted into additional fissile materials as part of the reaction.
Castle Bravo (Score:2)
OK, OK, alright already and read TFA, but TFA is silly.
A white dwarf is a vary old, end-stage star. What makes it old is that if it had been the ember of a larger, faster-burning star, it would have gone core-implosion supernova.
So then, would not the U235 content have half-lived away, and if the U is concentrated in the core, would not the low "enrichment" of the largely U238 precluded criticality?
Even if this mix of U235 and U238 could fission under the intense compression at the core of a white d
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U238 will happily fission if you compress it enough or bathe it in neutrons. The Czar Bomba was designed to have a 238 casing that would double its yield.
I don't think the impression the summary gives of a big core of uranium going boom is really correct. The white dwarf would be just at the edge of being hot enough to start fusing carbon. In a normal 1a supernova, extra material from a companion pushes it over that limit. If you had uranium collecting in the core fission could produce enough extra heat and
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They're just normally "touched off" by accreting mass that eventually overcomes the electron degeneracy pressure of the star's left over components.
This theory isn't that bizarre. A lot of things could "touch off" a Type 1a supernova. A big fucking fission explosion doesn't seem unreasonable at all.
Relativity (Score:4, Informative)
That's what I was thinking. Getting a fission explosion to occur is pretty tricky. The material has to be pure, and in the right shape, and pressure needs to be applied a certain way.
That being said, read up on the naturally occurring nuclear reactor in Gabon, Africa. Somewhat related, but still interesting.
https://en.wikipedia.org/wiki/... [wikipedia.org]
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Well at the pressures and heat in the core of a dead star, fission would be much more likely to happen spontaneously as the uranium etc settled into the core.
Even here, a cannon type fission explosion isn't that hard to arrange, just that it is not as practical as imploding a sphere.
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Perhaps, I'm far from expert on nuclear physics. OTOH, perhaps it is more like a hydrogen bomb, fission triggers fusion, which releases a lot of neutrons, which allow fission of materials like U238 that don't easily fission, which allows more fusion, which allows even more stuff to fission. Possibly this type of chain reaction doesn't happen until there's quite a bit of U235 and U238 in the core.
Anyways without studying and understanding their math and such, it's as much guess work.
It ignites the Fe and C (Score:2)
They fuse, generating the supernova.
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Few dozen, I believe the actual minimum number is 12.5kg or there about depends on how enriched your uranium is. That is a shade over one dozen, and certainly not a "few" dozen which would generally be at least more than two dozen.
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Well, that's what the summary says -- fission could *trigger* an explosion that would create a supernova from a white dwarf, a process that starts with heavier elements in the now dying star settling toward the core. TFA suggests this might be a mechanism by which dim supernovas (oxymoron noted) occur.
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Dead Stars (Score:1)
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They're saving this honorific for Keith Richards.
I feel . . . happy! (Score:2)
A white dwarf star is not quite dead yet.
Just like Keith Richards?
Sanctions! (Score:2)
For insterstellar peace and security!
Units (Score:2)
White dwarf supernovae light up their surroundings with the power of 5 billion Suns, and astronomers have used them as 'standard candles'...
But how many Libraries of Congress is this?
Re: Units (Score:1)
About umpteen siemens.
For example (Score:2)
Some Dead Stars May Harbor Enough Uranium To Set Off a Thermonuclear Bomb
Orson Wells, for example.
Not thermonuclear (Score:2)
1 : of, relating to, or employing transformations in the nuclei of atoms of low atomic weight (such as hydrogen)
They mean a fission bomb. Which is much less powerful than a hydrogen bomb, which all other stars are doing constantly. This article is clearly aimed at impressing those with no scientific exposure.
Re: Not thermonuclear (Score:3)
They do mean thermonuclear. The fusion reaction in a thermonuclear bomb is triggered by a fission explosion. This is exactly what they propose: a supernova caused by the fusion of oxygen and other light elements triggered by a fission reaction from the spontaneous assembly of trace amounts of heavy elements into a critical mass. This makes more sense than you'd think. While white dwarves don't have lots of heavy elements, they do have some, and it's not out of the question for one to have a critical mass's
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Just like what we do when exploding a thermonuclear bomb, the fission explosion creates a lot of neutrons, along with heat and pressure, triggering fusion, likely carbon fusion rather then hydrogen fusion.
It would be cases where the white dwarf was just a bit too small to fuse carbon without the push from the fission.
And here ... (Score:2)
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I worry more about America, who knows what nutcase might get elected in the future with it much too easy for a nutcase to push the button. Really there should be some sort of checks on that power.
Found the daily bullshit (Score:2)
Took me a moment: Uranium is doing fission. "Thermo-Nuclear" is fusion, with nothing heavier in there than Tritium. These two are pretty much at the opposite spectrum of things.
That is not to say the research referenced it BS, but this headline very much is.
Re: Found the daily bullshit (Score:3)
The article's headline does, in fact, make sense. The fusion reaction in a thermonuclear bomb is triggered by a fission explosion. This is exactly what they propose: a supernova caused by the fusion of oxygen and other light elements triggered by a fission reaction from the spontaneous assembly of trace amounts of heavy elements into a critical mass. This makes more sense than you'd think. While white dwarves don't have lots of heavy elements, they do have some, and it's not out of the question for one to h
Dead stars (Score:1)
Not A Good Analysis (Score:2)
The idea of actinides separating out preferentially to create a composition that can support a fission chain reaction in white dwarfs is interesting and does seem to merit further investigation. However their treatment of the subject of the effect this might have in the star is incompetent - and indicates they are working with a mental model of "white dwarfs explode, fission bombs explode, so maybe white dwarfs explode exactly like fission bombs" and I do mean "exactly like" as it is explicit in their analy
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The idea of actinides separating out preferentially to create a composition that can support a fission chain reaction in white dwarfs is interesting and does seem to merit further investigation. However their treatment of the subject of the effect this might have in the star is incompetent - and indicates they are working with a mental model of "white dwarfs explode, fission bombs explode, so maybe white dwarfs explode exactly like fission bombs" and I do mean "exactly like" as it is explicit in their analysis of the situation. This despite citing at the beginning the known natural fission reactions which most definitely did not result in an explosion (the Oklo Reactor in Gabon) which should have tipped them off that they were analyzing the situation all wrong
Except that your analysis of how fission happens on earth happens to be in a rather different environment than exists in the core of a white dwarf. Many of which are already right on the hairy edge of going boom for non-fission related reasons, and wouldn't need much of a kick to go over the edge. And the authors happen to be some of the most knowledgeable people on the planet about the physics of the middle of 1.4 solar masses of degenerate matter. So, probably not really that incompetent.
How do I know
No Chance (Score:2)
A white dwarf consists of matter supported by electron degeneracy pressure, and the critical mass for any Uranium would be quite small as all nuclei are already pushed into contact. The energy released would be de-minimums compared to the environment.
Elvis? (Score:2)
Curious. (Score:1)
So, how does the core receive enough neutrons to up-transmute?
Seems odd to me