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Cosmic Mystery Solved By Super-sized Supernova Dust

Soulskill posted about 7 months ago | from the now-developing-super-sized-cosmic-broom dept.

Space 16

astroengine writes: 'How cosmic dust is created has been a mystery for some time. Although the textbooks tell us that the dusty stuff that builds the planets — and, ultimately, the complex chemistry that forms life (we are, after all, made of 'star stuff') — comes from supernova explosions, astronomers have been puzzled as to how delicate grains of dust condense from stellar material and how they can possibly survive the violent shock waves of the cataclysmic booms. But now, with the help of a powerful ground-based telescope, astronomers have not only watched one of these supernova 'dust factories' in action, they've also discovered how the grains can withstand the violent supernova shock. "When the star explodes, the shockwave hits the dense gas cloud like a brick wall," said lead author Christa Gall, of Aarhus University, Denmark. "It is all in gas form and incredibly hot, but when the eruption hits the 'wall' the gas gets compressed and cools down to about 2,000 degrees. At this temperature and density elements can nucleate and form solid particles. We measured dust grains as large as around one micron (a thousandth of a millimeter), which is large for cosmic dust grains. They are so large that they can survive their onward journey out into the galaxy (PDF)." The surprising size of the measured dust particles means they can better survive the supernova's shockwave. This research has been published in the journal Nature.

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In Soviet America (-1)

Anonymous Coward | about 7 months ago | (#47418763)

NSA will not leave cosmic dust alone...

"gets compressed and cools down"? (4, Interesting)

jeffb (2.718) (1189693) | about 7 months ago | (#47418871)

I wish the author had elaborated a bit on this. I know that we're far away from the "ideal gas" regime here, and that things get independently wonky when you're dealing with supersonic flow, but "cooling down as it gets compressed" is so counter-intuitive that they should throw us at least a few lines of explanation.

Anybody here want to step up to the plate?

Re:"gets compressed and cools down"? (3, Funny)

ArcadeMan (2766669) | about 7 months ago | (#47418889)

I once had an A/C fall unto me, I totally understand being cooled down while getting compressed.

Re:"gets compressed and cools down"? (1)

ArcadeMan (2766669) | about 7 months ago | (#47418903)

An A/C once fell on me.

I cna't splel todya.

Re:"gets compressed and cools down"? (1)

Anonymous Coward | about 7 months ago | (#47419199)

I did no such thing.

Once again (0)

Anonymous Coward | about 7 months ago | (#47419165)

Once again an almost total lack of quality story in a physics story. I await the "tweaks"...and ultimately the retractions.

Re:"gets compressed and cools down"? (1)

swm (171547) | about 7 months ago | (#47419265)

The only thing I can think is it works like a refrigerator.
The shock wave compress the the dust, which raises its temperature, so it radiates heat (a lot of heat: P ~ T^4).
When the shock wave passes, the dust expands and cools back down below its original temperature.

Re:"gets compressed and cools down"? (5, Informative)

mdsolar (1045926) | about 7 months ago | (#47419411)

Cooling is radiative post-shock. The denser plasma cools more efficiently, proportional to the square of the electron density for a hydrogen plasma cooled by free-free radiation.

Re:"gets compressed and cools down"? (4, Funny)

RenderSeven (938535) | about 7 months ago | (#47419619)

That must be insightful, I didnt understand a word of it.

Re:"gets compressed and cools down"? (2)

mdsolar (1045926) | about 6 months ago | (#47422095)

jeffb was thinking about gas heating when it is compressed and cooling when it is rarefied. But the effect of compression is to allow more efficient cooling by radiation which pulls energy from the plasma (ionized gas). One means of radiation comes from electrons changing direction in the vicinity of other electrons. This is called free-free radiation. Bound states can also be excited by collisions with free electrons and when they radiate that removes energy from the gas. This is called bound-free radiation. I'm not sure if that helps or just baffles further.

Thank you. (1)

jeffb (2.718) (1189693) | about 7 months ago | (#47419667)

I can imagine how that would be the case, although I certainly couldn't derive it.

Re:"gets compressed and cools down"? (0)

Anonymous Coward | about 6 months ago | (#47420987)


Re:"gets compressed and cools down"? (1)

davester666 (731373) | about 6 months ago | (#47422497)

Are you sure cosmic dust isn't just the pool cue chalk that came off the cue when God was playing pool with the planets?

Big Dust? - Rocks 101 (1)

Tablizer (95088) | about 7 months ago | (#47418967)

"Big dust" is "sand". Big sand is pebbles. Big pebbles are rocks. Big rocks are boulders. Big boulders are mountains. Big mountains are planets. Big planets are stars. Big stars are something you don't want to be around.

Re:Big Dust? - Rocks 101 (1)

symbolset (646467) | about 6 months ago | (#47421873)

"Rocks for Jocks"

More telescopes, less particle accelerators please (1)

Sla$hPot (1189603) | about 6 months ago | (#47422953)

There is so many things happening in front of our noses when looking into the sky. But we just don't see it.
Sub atomic particles are orders of magnitude more energetic, than what we can achieve here on earth.
Star births, supernovas and gamma ray bursts happen regularly, just waiting to be detected, recorded and analyzed.
More and more detailed data on extrasolar planets are gathered every day.
More telescopes please!
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