NuSTAR telescope takes first peek into core of supernova

Feb 19, 2014 by Robert Sanders
NuSTAR telescope takes first peek into core of supernova
Stars fuse hydrogen (H) and helium (He) into heavier elements to produce energy, but once the reactions reach iron (Fe), fusion stops and the star implodes, creating a compact object – a neutron star or black hole – and blowing off the star’s outer layers in a supernova explosion. The explosion seeds the galaxy with elements like carbon (C) and oxygen (O) essential to life. Credit: NASA image.

(Phys.org) —Astronomers have peered for the first time into the heart of an exploding star in the final minutes of its existence. The feat by the high-energy X-ray satellite NuSTAR provides details of the physics of the core explosion inaccessible until now, says team member Steven Boggs of UC Berkeley. NuSTAR mapped radioactive titanium in the Cassiopeia A supernova remnant, which has expanded outward and become visible from Earth since the central star exploded in 1671.

Astronomers for the first time have peered into the heart of an exploding star in the final minutes of its existence.

The feat is one of the primary goals of NASA's NuSTAR mission, launched in June 2012 to measure high-energy X-ray emissions from exploding stars, or supernovae, and , including the massive black hole at the center of our Milky Way Galaxy.

The NuSTAR team reported in this week's issue of the journal Nature the first map of titanium thrown out from the core of a star that exploded in 1671. That explosion produced the beautiful supernova remnant known as Cassiopeia A (Cas A).

The well-known supernova remnant has been photographed by many optical, infrared and X-ray telescopes in the past, but these revealed only how the star's debris collided in a shock wave with the surrounding gas and dust and heated it up. NuSTAR has produced the first map of high-energy X-ray emissions from material created in the actual core of the exploding star: the radioactive isotope titanium-44, which was produced in the star's core as it collapsed to a neutron star or black hole. The energy released in the core collapse supernova blew off the star's outer layers, and the debris from this explosion has been expanding outward ever since at 5,000 kilometers per second.

"This has been a holy grail observation for high energy astrophysics for decades," said coauthor and NuSTAR investigator Steven Boggs, UC Berkeley professor and chair of physics. "For the first time we are able to image the radioactive emission in a supernova remnant, which lets us probe the fundamental physics of the nuclear explosion at the heart of the supernova like we have never been able to do before."

"Supernovae produce and eject into the cosmos most of the elements are important to life as we know it," said UC Berkeley professor of astronomy Alex Filippenko, who was not part of the NuSTAR team. "These results are exciting because for the first time we are getting information about the innards of these explosions, where the elements are actually produced."

NuSTAR telescope takes first peek into core of supernova
Superimposed images of the Cas A supernova remnant taken by NASA’s Chandra and NuSTAR orbiting telescopes. Red and green are X-ray emissions detected by Chandra of heated iron and silicon/magnesium, respectively, while blue shows NuSTAR’s map of the distribution of titanium produced in the core of the explosion 340 years ago. Credit: NASA/NuSTAR image.

Boggs says that the information will help astronomers build three-dimensional computer models of exploding , and eventually understand some of the mysterious characteristics of supernovae, such as jets of material ejected by some. Previous observations of Cas A by the Chandra X-ray telescope, for example, showed jets of silicon emerging from the star.

"Stars are spherical balls of gas, and so you might think that when they end their lives and explode, that explosion would look like a uniform ball expanding out with great power," said Fiona Harrison, the principal investigator of NuSTAR at the California Institute of Technology. "Our new results show how the explosion's heart, or engine, is distorted, possibly because the inner regions literally slosh around before detonating."

Expanding supernova remnant

Cas A is about 11,000 light years from Earth and the most studied nearby supernova remnant. In the 343 years since the star exploded, the debris from the explosion has expanded to about 10 light years across, essentially magnifying the pattern of the explosion so that it can be seen from Earth.

Earlier observations of the shock-heated iron in the debris cloud led some astronomers to think that the explosion was symmetric, that is, equally powerful in all directions. Boggs noted, however, that the origins of the iron are so unclear that its distribution may not reflect the explosion pattern from the core.

"We don't know whether the iron was produced in the , whether it was part of the star when it originally formed, if it is just in the surrounding material, or even if the iron we see represents the actual distribution of iron itself, because we wouldn't see it if it were not heated in the shock," he said.

The new map of titanium-44, which does not match the distribution of iron in the remnant, strongly suggests that there is cold iron in the interior that Chandra does not see. Iron and titanium are produced in the same place in the star, said UC Berkeley research physicist Andreas Zoglauer, so they should be similarly distributed in the explosive debris.

"The surprising thing, which we suspected all along, is that the iron does not match titanium at all, so the iron we see is not mapping the distribution of elements produced in the core of the ," Boggs said.

He and his UC Berkeley colleagues also launch balloon-borne high-energy X-ray and gamma-ray detectors to record the radioactive decay of other elements, including , in supernovae to learn more about the nuclear reactions that take place during these brief, catastrophic explosions.

"The radioactive nuclei act as a probe of supernova explosions and allow us to see directly into densities and temperatures where nuclear processes are going that we don't have access to in terrestrial laboratories," Boggs said.

NuSTAR continues to observe radioactive titanium-44 emissions from a handful of other to determine if the pattern holds for other supernovae as well. These supernova remnants must be close enough to Earth for the debris structure to be seen, yet young enough for radioactive elements like titanium – which has a 60-day half-life – to still be emitting high-energy X-rays.

Explore further: Mach 1000 shock wave lights supernova remnant

More information: Study paper: dx.doi.org/10.1038/nature12997

add to favorites email to friend print save as pdf

Related Stories

Radioactive decay of titanium powers supernova remnant

Oct 17, 2012

(Phys.org)—The first direct detection of radioactive titanium associated with supernova remnant 1987A has been made by ESA's Integral space observatory. The radioactive decay has likely been powering the ...

A star explodes, turns inside-out

Mar 29, 2012

(PhysOrg.com) -- A new X-ray study of the remains of an exploded star indicates that the supernova that disrupted the massive star may have turned it inside out in the process. Using very long observations ...

The remarkable remains of a recent supernova

Jun 26, 2013

(Phys.org) —Astronomers estimate that a star explodes as a supernova in our Galaxy, on average, about twice per century. In 2008, a team of scientists announced they discovered the remains of a supernova ...

Mach 1000 shock wave lights supernova remnant

Nov 25, 2013

When a star explodes as a supernova, it shines brightly for a few weeks or months before fading away. Yet the material blasted outward from the explosion still glows hundreds or thousands of years later, ...

Recommended for you

Image: Galactic wheel of life shines in infrared

Oct 24, 2014

It might look like a spoked wheel or even a "Chakram" weapon wielded by warriors like "Xena," from the fictional TV show, but this ringed galaxy is actually a vast place of stellar life. A newly released ...

New window on the early Universe

Oct 22, 2014

Scientists at the Universities of Bonn and Cardiff see good times approaching for astrophysicists after hatching a new observational strategy to distill detailed information from galaxies at the edge of ...

User comments : 32

Adjust slider to filter visible comments by rank

Display comments: newest first

kevin_hingwanyu
not rated yet Feb 23, 2014
In the picture the core of the star is iron. When some stars composed with similar materials (Fe) are to collapse into black holes, the gravity and pressure 'in front' and 'behind' of event horizon are large. I guess that those materials falling toward singularity are only protons, neutrons and electrons ? I speculate those Fe, Ni and all heavy elements are no longer existed under the pressure and gravity ? Fission might take place for the heavy elements changing to hydrogen ? Whereas the fission of Fe . . . etc to H are supposedly endothermic, I guess no particle is heavier than hydrogen (e.g. neutron stars) when they are near black holes ?

A sphere/cloud of hydrogen generates energy with fusion, from H to Fe. Those energy had radiated into space long ago. When the same sphere/star collapses into a black hole, it requires to absorb energy for fission(?), from Fe and other heavy elements to H.
] . . .
kevin_hingwanyu
not rated yet Feb 23, 2014
. . . [
And when mass accelerates towards singularity (probably moving along a circular path e.g. spirally inward/accretion disc) at relativistic speed, nearly some fractions of light speed, that absorbs energy too. Where those energy come from ?

That is, H -> Fe + energy1, and energy1 radiated away,
then, Fe + energy2 -> H, where the energy2 comes from ?
and mass at speed 0 + energy3 -> mass near speed of light,
I speculate when v=sqrt(3)/2 of c the twice the mass.
Does the energy come from the potential energy between the space of atoms ?

Also, I guess when a black hole "does not have enough energy or mass" (comparative to those massive black holes), the material (origin from the star) falling into singularity might be heavier than hydrogen but still much less than Fe, despite some of the original composition are Fe.
cantdrive85
1 / 5 (3) Feb 23, 2014
A pathetically inept understanding of Marklund Convection results in confusion of the physics involved here. This is hardly surprising though considering astrophysicists complete ignorance of experimentally based plasma physics. They prefer the fanciful models "we know to be wrong" to the exceedingly complex models which are much closer to reality. Problem is nearly all of the highly intelligent critical thinkers have been weeded out of the graduate programs in favor yes men cheerleaders of metaphysical theories such as the BB and GR.
Captain Stumpy
5 / 5 (2) Feb 23, 2014
considering astrophysicists complete ignorance of experimentally based plasma physics

@cantdrive
TROLL
personal conjecture
there is plenty of evidence to support that modern astrophysicist understand plasma
see:
http://iopscience...1_41.pdf &
http://phys.org/n...ack.html &
http://arxiv.org/.../0512549 &
http://phys.org/n...ggs.html &
http://phys.org/n...ank.html
http://phys.org/n...end.html

Problem is nearly all of the highly intelligent critical thinkers have been weeded out of the graduate programs

personal conjecture not supported by facts
They prefer the fanciful models "we know to be wrong" to the exceedingly complex models which are much closer to reality

intentional LIE = TROLLING
see above
cantdrive85
1 / 5 (2) Feb 24, 2014
Stalking me? Who's the troll?

Simpleton.
Tim Thompson
5 / 5 (4) Feb 25, 2014
A pathetically inept understanding of Marklund Convection results in confusion of the physics involved here.

There is no such thing as "Marklund Convection", that's just a buzzword invented by pseudoscientists so they can look smart (at least to themselves). If you wanted to try to get it close to right, you would call it "Marklund diffusion", although in fact you can search the plasma physics & plasma engineering literature until you are "blue in the face" and not find any reference to either one anywhere, which is what we sophisticated types call "a clue" to the true nature of its true importance.

But, giving the benefit of the doubt, and assuming there is a Marklund diffusion process to talk about, why do you think it is relevant to this particular discussion?
Tim Thompson
5 / 5 (4) Feb 25, 2014
I guess that those materials falling toward singularity are only protons, neutrons and electrons ? I speculate those Fe, Ni and all heavy elements are no longer existed under the pressure and gravity ?

When the iron core reaches a temperature about 3,000,000,000 Kelvins, the photon bath destroys the iron nuclei completely, and we are left with free protons & neutrons & electrons (which under extreme pressure can combine with the protons to create more neutrons). The unbound particles can pack far more tightly and free-fall at a large fraction of the speed of light. With the floor pulled out from under it, the rest of the star falls very fast too. When it all smashes together at the center, the result is the supernova explosion, which leaves behind a neutron star. If more stuff falls on the neutron star, it then collapses to a black hole (which will happen for a very massive, like 20 solar mass, star).
kevin_hingwanyu
5 / 5 (1) Feb 25, 2014
When the iron core reaches a temperature about 3,000,000,000 Kelvins, the photon bath destroys the iron nuclei completely, and we are left with free protons & neutrons & electrons
Iron converted back to hydrogen, carbon, helium and neutrons are nuclear fission which are the reverse of fusion. Those reactions absorb energy. For the creation of neutron star, I guess the energy comes from the fusion/compression of hydrogen and neutrons where the output is to create one super (neutron) atom - neutron star ?
for stars: H -> Fe + energy(1);
for neutron stars: Fe -> protons + electrons + neutrons -> neutron stars + energy(2), where energy(2) fuels the nuclear fission of Fe, and energy(2) much >> energy(1) ?
] . . . [
kevin_hingwanyu
not rated yet Feb 25, 2014
] . . . [
For the creation of black hole, I speculate that those p+, e- and n0 (source from Fe and other heavy elements of the original star after undergoing of fission) flowing into black hole where those protons, e- and neutrons are at some special states which are different from those comparative to the cores of normal stars ? This attempts to explain what fuels the fission of Fe ? Or, this shows that the creation of black holes output much energy than the creation of neutron stars, they both generate much energy than the fusion of H -> Fe ?
Tim Thompson
5 / 5 (2) Feb 25, 2014
Iron converted back to hydrogen, carbon, helium and neutrons are nuclear fission which are the reverse of fusion. Those reactions absorb energy.

Not in this case. Fission is the spontaneous splitting of a nucleus with an unstable structure to begin with; that is an internal process and does emit energy. In a chain reaction the fission can be induced by neutrons of appropriate energy, but only if the nuclei were unstable to begin with, and would have eventually fissioned all by themselves. Iron-56 is stable and has the highest binding energy per nucleon of any element. It does not fission. In this case, the photons literally rip the iron nuclei directly into free protons & neutrons and very little of anything else, if any. This is very different from common nuclear fission.
GSwift7
5 / 5 (2) Feb 26, 2014
In this case, the photons literally rip the iron nuclei directly into free protons & neutrons and very little of anything else, if any. This is very different from common nuclear fission


I think maybe Kevin is a little confused about what is being described.

As I understand the theory: When the collapse happens, it's only the inner part of the star that collapses, maybe only the iron core itself. This happens so fast (seconds) that the outer parts of the star are still basically right where they were. When the core reaches max compression, some of it bounces off the center and back out through the rest of the star, which is still basically standing where it was a few seconds ago. When that billion degree iron goes shooting back out through the stationary material in the other layers, it hits hard enough to fuse into atoms heavier than iron, and blow them out into space. The majority of energy is kinetic, not fusion/fission products. Simple momentum at relativistic scales. :)
kevin_hingwanyu
not rated yet Feb 27, 2014
@Tim Thompson
The previous terminology "fission" simply refers to the idea splitting of atom, any atom, whatever elements heavier than Fe, lighter than Fe, or Fe. It attempts to describe some processes that to convert heavier atomic nucleus to lighter nucleus. For elements with atomic number much much higher than Fe-56 their nuclei are usually unstable and tend to undergo fission with releasing of energy, and the final products are lighter elements. The nucleus of Fe are the most stable among other natural elements, so to say fission of Fe is not very clear. The idea is that, during the creation of black hole or neutron star, the original Fe of a star is converted to p+, e- and n0. How the change takes place ? Probably it is not the spontaneously decay of Fe, or Fe fission to hydrogen and neutrons, very impossible. The idea comes where H is to fusion to He, carbon, nitrogen and oxygen, subsequently to silicon and iron. All(?) are output energy.
[ . . .
kevin_hingwanyu
not rated yet Feb 27, 2014
. . . ]
One of the conjecture is that splitting of Fe -> proton + e- + n0 may absorb energy, but it should absorb energy because same amount of p+ e- n0 fusion to Fe releasing energy. If photons and the high temperature electrons are to change Fe to p+, e- and n0, where the energy comes from ?
kevin_hingwanyu
not rated yet Feb 27, 2014
@GSwift7
quote "When the core reaches max compression, some of it bounces off the center"

And perhaps some of the iron travel across the core to fuse with iron or other elements on the other/opposite side of the core during the max compression. Neutron stars probably contain no iron, but it is very possible neutron stars are converted by stars with large amount of iron. For black holes, layperson's view, I realise that the materials (e.g. where the source is from the original star specifically) flowing into black hole are protons, electrons and neutrons, or no material nor element is heavier than hydrogen. And similar to the precursors of neutron stars probably the original star for the formation of black hole contains large amount of iron. I guess the materials to produce neutron star or black hole are nearly 100% protons, neutrons and electrons . . . etc. Then where the energy comes from, that is, the energy to split iron to p+, e- and n0 ? For supernovae, this not a problem.
Tim Thompson
5 / 5 (3) Feb 28, 2014
When the core reaches max compression, some of it bounces off the center and back out through the rest of the star, which is still basically standing where it was a few seconds ago.

The outer layers don't "stand still", they fall, and they fall very fast because they feel a substantial gravitational force. So the outward bouncing core hits in infalling outer layers, and that makes the bang of the supernova explosion a lot stronger. Heavy elements are built up in the aftermath primarily by neutron absorption and beta decay of unstable isotopes. None of the core iron survives, the iron we see is almost all made in the supernova aftermath.

Here are a couple of good papers on the topic, and you can follow references & citations as well.

http://adsabs.har...85..245B
http://adsabs.har...42...38J
Tim Thompson
5 / 5 (3) Feb 28, 2014
I guess the materials to produce neutron star or black hole are nearly 100% protons, neutrons and electrons . . . etc. Then where the energy comes from, that is, the energy to split iron to p+, e- and n0 ? For supernovae, this not a problem.

The ultimate source of energy is the gravitational field of the collapsing star. The super high core temperature (maybe 3,000,000,000 Kelvins) comes from gravitational pressure. The temperature is responsible for destroying the degenerate core iron, which collapses under its own gravity. So this is a mechanism that converts gravitational energy into thermal & mechanical energy.
kevin_hingwanyu
not rated yet Mar 02, 2014
@GSwift7 and @Tim Thompson
The outer layers don't "stand still", they fall, and they fall very fast because they feel a substantial gravitational force


In the picture, and other pictures for the composition of the core of supernovae in wikepedia.org, suppose the radius of star=r and roughly radius of Fe core =0.1r.
Layperson's view, I think the discontinuous output of the radiation-pressure is rather the main reason for the speedy collapse of the **outer shell** of supernovae. The radiation pressure against gravity maintains the balance of stars.

My conjecture is that [
once the fuel of a star is insufficient, the Fe core is the "first"/earliest part to respond/react to it. The Fe core is the most pressurised part not only due to its location, but also due to iron's atomic weight and gaseous/fluid density. Radiation energy is supposedly to radiate outwardly measuring from the center of star.
. . [
kevin_hingwanyu
not rated yet Mar 02, 2014
] . .
The iron core never has fusion which produces no energy. Where fusions generating energy are the onion shells next to the core such as the shells of Si, O, C . . . etc. It is realised that the radiation energy is the largest near the center of star.

When star begins to collapse, that is, radiation pressure is low. The Fe core is the first to respond to the event because the Fe "core" is near the "center", and it sustains the weight of the whole star. And this effect of low radiation pressure continues to propagate throughout the rest parts of the star. The speed of falling into the center no doubt the Fe core is the fastest. While Fe core falling towards the center, the outer shells of the star should experience/measure the same gravitational force as before. The mass enclosed in the sphere of Gauss with radius=0.1r remains the same(within some short period).
. . [
kevin_hingwanyu
not rated yet Mar 02, 2014
] . .
The shrunk core, and the Fe core before the contraction, exert exactly the same gravity to the outer shells (at short time only). When the core shrinks, the outer shells (within short period of time) do not accelerate toward the center too fast as the initial velocities are approximately zero.

The shrinking core creates a (relatively) low pressure shell/region and surrounded by this (relatively) low pressure shell. With the core enclosed by this low pressure shell, the particles/gases of outer shells with Maxwell's gaseous speed would not be too slow moving towards center no matter whether they are ideal gas or not.

What interesting is, during the contraction of the core, probably the fusions of lighter elements are continuing, providing the continued radiation pressure to slowing down the contraction of outer shells.
. . [
kevin_hingwanyu
not rated yet Mar 02, 2014
] . .
But what really interesting is, when the said low pressure shell spreads outward. This (relatively) low pressure shell/region must shutdown all reaction centers on its path, because one of the conditions for fusion altered - sufficiently high pressure. What dramatically interesting is, with this low pressure feature, while the outer shells are sucked toward center, the temperature of these gases also drops sharply, an unexpected discovery. It dissatisfies another condition for fusion - enough high temperature.

The further problem is that these fusion reaction centers at outer shells stop output radiation pressure. They (fusion reaction centers next to the core and other outer shells, e.g. the shells of Si, oxygen) are also shrinking themself - an induced contraction by the travelling low pressure shell. Well, thinking along these logic, it is surprisingly to discover that not only the iron core collapse, the rest of the star next to the core shrink by themselves too.
. . [
kevin_hingwanyu
not rated yet Mar 02, 2014
] . .
The conclusion of my conjecture is:
-(1) the iron core shrinks because of large gravitational force;
-(2) a (relatively) low pressure shell/region travels outward from the iron center;
-(3) along the path of the travelling low pressure shell:
(3a) pressure drops;
(3b) local fusion reaction center shutdown therefore supplying of radiation pressure stops;
(3c) temperature drops;
(3d) contraction induced locally;
(3e) the (3d), this induced contraction may be called **induced chain contraction** which deteriorates the fusion of the whole star and exponentially speeds up the collapsing of the entire star.
. . [
kevin_hingwanyu
not rated yet Mar 02, 2014
] . .

Logically, it is generally realised that the iron core shrinks because of large gravitational force. With this thought experiment it is surprised to discover that the outer shells and the entire star perhaps collapse much fast than expected with the **induced chain contraction**.

These only are personal view of a layperson.
}

Supernova - The Induced Chain Contraction

<> end of the conjecture <>.
kevin_hingwanyu
not rated yet Mar 02, 2014
@GSwift7 and @Tim Thompson

Quote, "When the core shrinks, the outer shells (within short period of time) do not accelerate toward the center too fast as the initial velocities are approximately zero."

I think
"When the core shrinks, the acceleration of outer shells (within short interval) toward the center has no difference comparing before the contraction of the iron core."
is better.
kevin_hingwanyu
not rated yet Mar 05, 2014

So this is a mechanism that converts gravitational energy into thermal & mechanical energy.

So the energy comes from the potential energy between the space of atoms/protons. Then it exists some processes which can generate much more energy than (the total energy released by) the fusions of H -> He . . . -> Si . . . etc . . -> Fe. They are some processes for the 'fusion'/compression of materials from progenitor star to neutron star. The known effects of these energy are: (1) to change iron atoms and other atoms into neutron star; (2) to provide the brightness and kinetic energy for supernovae; (3) to supply energy for the spin, and the effects for the electromagnetism, for neutron stars or pulsars.

For black holes, the compression of same amount of materials releases further much more energy.
kevin_hingwanyu
not rated yet Mar 05, 2014
The super high core temperature (maybe 3,000,000,000 Kelvins) comes from gravitational pressure

In my conjecture - the "Induced Chain Contraction", I speculate when the core of a star collapse, the outer layers would move very fast toward the center. The explanation may be the Maxwell-Boltzmann gaseous speed instead of gravitational force. I find equations source from wikipedia.org which is: the most probable speed = vp = square_root (2 kT/m)
= square_root (2 RT/M), using spreadsheet I find the same answer for diatomic nitrogen at 300 K, gives vp = 421.7 m/s. Therefore, I use Fe=1 x 56, T=10^6 K, e.g. the atmospheric corona for Sun for iron, then it gives vp = 296,428 km/s = 0.988 c. The coronal particles travel at relativistic speed. In the core of stars T ~= 3 x 10^9 K, are the particles moving at almost the speed of light ? Even the speed of collapse of the core is near the speed of light, the outer shells can always move fast enough to catch up the low pressure shell/zone ?
stellar-demolitionist
not rated yet Mar 05, 2014
Kevin:

First, your scaling for Fe (in the core or the corona) are of a bit. At 3 GK the temperature is 10,000,000 times room temperature. This will increase the typical speed. An Fe nucleus is twice as massive as a N2 molecule. This will decrease the speed. We need to multiply your estimate for N2 in air by SQRT(10 000 000/ 2) which is about 2200. This will increase the velocity to about 1000 km/s which is still considerably lower than the speed of light
stellar-demolitionist
5 / 5 (2) Mar 05, 2014

When the iron core reaches a temperature about 3,000,000,000 Kelvins, the photon bath destroys the iron nuclei completely, and we are left with free protons & neutrons & electrons (which under extreme pressure can combine with the protons to create more neutrons).


Tim, this is an out-of-date picture of Fe-core collapse. (Unfortunately it persists in may "authoritative" sources.) H. Bethe showed in 1979 that the Fe nuclei don't break up to trigger (or during) collapse. Photons in a 3 GK gas just aren't energetic enough. There is some equilibrium rearrangement of the nuclei with nucleons being knocked free and then captured by other nuclei during collapse and electron captures do convert some protons to neutrons within nuclei, but nuclei are the dominant constituent of the collapsed core until the densities squeeze the nuclei together as nuclear matter. Only when the core rebound shock heats the nuclei to much higher (at least 30 GK) temps do nuclei dissociate.

Cheers.
Tim Thompson
5 / 5 (3) Mar 05, 2014
H. Bethe showed in 1979 that the Fe nuclei don't break up to trigger (or during) collapse.

Thanks. I was unaware of that. I have read the paper, and looked to see if I could find any modification of the conclusions in the copious references, but I don't find any, and Burrows (2013) continues to cite & agree with Bethe et al. I did not expect it to be such a low entropy process, and it's a lot more complicated than I would have guessed; the nuclei break into alpha particles early on, but then re-form heavier nuclei at high density, until the pressure forces the heavier nuclei into "one big nucleus".

For everyone else:
"Equation of state in the gravitational collapse of stars"; H.A. Bethe, et al., Nuclear Physics A 324(2-3): 487-533 (July 1979)
http://adsabs.har...24..487B

"Colloquium: Perspectives on core-collapse supernova theory"; Adam Burrows, Reviews of Modern Physics 85(1): 245-261 (January 2013)
http://adsabs.har...85..245B
kevin_hingwanyu
not rated yet Mar 06, 2014
This will increase the velocity to about 1000 km/s which is still considerably lower than the speed of light

The velocity around 1000 km/s for gaseous Fe at 3 GK inspires the thinking for the mechanism. The (relatively) low pressure shell/layer created by the collapse of the iron core will persist much longer than expected because the outer shells attracted by exactly the same gravitational force, and the gaseous speed is 'not too fast', providing if the iron core shrinks at very high speed. That the effects of the shutting down of local fusion reaction zones are much profound, first the alteration of reaction pressure for fusion, then the discontinuous supply of radiation pressure subsequently decreasing the reaction temperature. The effects of both factors will induce contraction locally. The inner parts of the star will shrink exponentially by the collapse of the iron core.
. . {
kevin_hingwanyu
not rated yet Mar 06, 2014
} . .
Comparing protons with N2 the sq_root(10,000,000 x 28) = ~17,000. The typical speed is approximately 6800 km/s which is still far from the speed of light but these effects are productive. With these effects, the "Induced Chain Contraction" conjecture can be modified much better to explain some features of supernovae.
kevin_hingwanyu
not rated yet Mar 08, 2014
Update: It exists some processes which the energy released are more than nuclear fusion where the origin of the energy is the potential energy between the space of nuclei.
kevin_hingwanyu
not rated yet Mar 08, 2014
Suppose the surface gravity of some white dwarf is 100,000 times that of Earth. Then acceleration is 1000 km s^-2. The distance of free falling is 1000(?) km at first second, then 4000(?) km and 9000(?) km, at 2 s and 3 s respectively. The (previously) supposed 6800 km/s Maxwell-Boltzmann gaseous speed is much fast, where in 3 s the distance is 20,000 km. (The core temperature of this supposed white dwarf is lower than the collapsing star.)

Suppose some white dwarf is 0.04 solar diameter approx. 1,390,000 km x 0.04, ~ 56,000 km.

Suppose the speed of collapse of the iron core is much more fast than the above velocities, then the hypothesis for the "induced chain contraction" mechanism is useful.

Those "gases" are not ideal gas. Besides that they are plasma it is important. The motion of the fluid affected by gaseous speed, gravitational attraction and electromagnetism, the resulting effects are probably COMPLETELY different which require further estimations and calculations.