back to article Cosmic dust riddle BREAKTHROUGH: Study tackles stuff of the universe

Astronomers have long wondered where all the strange dust that hangs about in space originates. They're also interested in how all the cosmic dust clouds form despite all the solar flares, supernovas and other potentially dust-blasting events. A new study that was published in Nature this week may provide some answers. The …

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Neat

Thumbs up for taking a new look at something I'm sure a lot of people have looked at and thought a)I wonder why that happens (and thought no more about it) or b)They probably worked this out years ago (but I don't know where to find the answer).

Now there is an answer (well perhaps the start of a fuller explanation?)

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Gas gets compressed and cools down?

Is there something going on there to lose the heat - conduction to the shell, perhaps? It ought to get hotter when you squash it...

(Yes, I know temperature does not equal thermal energy - I'm trying to work out what's going on.)

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This post has been deleted by its author

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Re: Gas gets compressed and cools down?

(Sorry Neil, my withdrawn post made an incorrect assumption about the subject you were asking about.)

It may be that the shockwave forces 'order' onto the hot, dense and diffuse cloud, thus inducing a phase change and effectively 'flushes out' thermal energy. An expert might come along if we wait a while.

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@Neil Barnes

Compression heats gas up BUT after it has been compressed the higher density gas can cool off much faster (because the radiation mechanisms are more efficient) so the net effect is to cool it.

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Re: @Neil Barnes

Ah, so it's the pulse causing a compression and rarefaction that allows the radiation, then.

Thanks.

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Anonymous Coward

"Compression heats gas up..."

"...BUT after it has been compressed the higher density gas can cool off much faster"

Thanks for the clarification. I'm grateful because it means I can still trust my bicycle whose tyres will heat up when I force air into them.

(I never bothered about the speed with which it then cools down again.)

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Re: Gas gets compressed and cools down?

I was thinking the same thing. Something important has been omitted from the summation, as Boyle's Law predicts that the particles should heat up when compressed, not cool down.

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Re: Gas gets compressed and cools down?

Temperature refers to the velocity of the particles. Naturally, when the particles hit the dense wall of gas and slow, they are, therefore, cooler.

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Anonymous Coward

Re: "Compression heats gas up..."

"Thanks for the clarification. I'm grateful because it means I can still trust my bicycle whose tyres will heat up when I force air into them."

The science says that if you force enough air into the tyres, they will get hot enough to become lighter than air and you will then be able to fly.

: )

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What is the 'shockwave' made of?

And what sort of size are the dust particles?

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Re: What is the 'shockwave' made of?

A star is a fairly dense ball of gas (Sun's average is about 1.6 x density or water). When the star's core finally collapses not all of the star gets to form the remnant neutron star/black hole. There is a rebound shock wave generated in the remaining gas (now going outwards) which is the explosion blowing it all away. When this fast moving gas hits the shell(s) of gas and dust previously expelled from the star it forms the shock wave. It's this that generates the photons seen by us and other wavelength instruments; the photons from within the star are adsorbed by it's gas and don't get seen.

All elements heavier than iron are generated during the rebound compression of the non core part of the star. Normal fusion can't 'burn' heavier than iron even in massive stars.

During the actual core collapse massive numbers of neutrinos are generated; these are not adsorbed and as they move damned near c we see them first and then the visible flash later when the shock wave eventually hits the shells and generate broad spectrum photons.

By the by, current thoughts are that some forms of dust and mixed element molecules are formed by quantum-chemistry in gas in the colder parts of space. Low temperature = slow moving and gives time for electron shells to interact when they are close, not like our normal terrestrial chemistry where they have to based into each other with heat (fast brownian motion).

Sorry but I don't rate the clarity of the article much.

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Re: What is the 'shockwave' made of?

"During the actual core collapse massive numbers of neutrinos are generated; these are not adsorbed..."

According to the main theory they sometimes are, and are responsible for the bulk of the visible explosion:

http://en.wikipedia.org/wiki/Supernova#Core_collapse

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Childcatcher

Re: What is the 'shockwave' made of?

"Sorry but I don't rate the clarity of the article much."

Thanks for the explanation. It was quite helpful. Some of the article goes beyond not being clear, though.

Once the hydrogen is all gone and no more energy can be extracted from the fusion process, the star dies and giant clouds of gas....

No, there's still hydrogen left at that point and fusion is still producing energy, just not enough to maintain equilibrium with gravity. What are those "giant clouds of gas" mostly made of?

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at 2:08

" .. the Deathstars can give rise to a multitude of cosmic fireworks ...."

I saw a film about that.

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Anonymous Coward

Re: at 2:08

Yeah, and many boffins died to bring us this information. LOL

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Mushroom

yeah but

OK they have worked out where the dust comes from but where does all that fluff originate. <looks under bed> A prize for the first person to mention shockwaves :)

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Anonymous Coward

Re: yeah but

Fluff cannot be created or destroyed, it can only be changed from one form to another.

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Joke

Re: yeah but

It's SO Fluffy!!!

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Mystery was cracked in January

Supernova were picked as the source of cosmic dust quite some time ago, though the process described in this article may be a new discovery. The first photos of cosmic dust creation were captured in January of this year:

https://public.nrao.edu/news/pressreleases/alma-images-supernova-dust-factory

http://www.bbc.com/news/science-environment-25633545

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Ah.. good.

Now that we know where the dust comes from, I'll let the wife know that the dust doesn't come from either myself or the dog and that it's not our fault.

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Rol
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As I've explained many times

the dust on my workstation is proof of my explosive activity and not as you assume, total lack of effort and sloth like pace.

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this is why that happens

under zero gravity the main attractive force are electrostatic forces.

and on a massive schale even with huge stellar blasts, it doesnt matter, the moving of particles will create elctromagnetic fields, and particles in such environments atrack each.

Huge stellar blasts will only shake those fields more, and thus create more charge.

If those scientist would have taken some looks to experiments allready done in the space shuttle they would have know this.. (a few years ago)...

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Re: this is why that happens

Let me guess, you are here to sell the PLASMA THEORY OF THE UNIVERSE?

and on a massive schale even with huge stellar blasts, it doesnt matter, the moving of particles will create elctromagnetic fields, and particles in such environments atrack each.

lolno.

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