[meteorite-list] Chondrule formation mechanism (Info Please)

From: E.P. Grondine <epgrondine_at_meteoritecentral.com>
Date: Fri Oct 27 12:29:05 2006
Message-ID: <20061027162900.66799.qmail_at_web36904.mail.mud.yahoo.com>

Hi Sterling -

You left "foaming" after a "release of gravitational
pressure" out of you list of hypothetical chondrule
formation mechanisms.

It seems to me that Sears theory hits the same
problems presented by chondrule dating that the
"foaming" theory faces. I wonder how he got around
that constraint?

good hunting,
Ed



--- "Sterling K. Webb" <sterling_k_webb_at_sbcglobal.net>
wrote:

> Hi, Rob, Pete, Ed, List,
>
> Rob wrote:
> > The iron is formed in the cores of all stars.
> > Nuclearly speaking it is the stablest of all
> elements
> > (lowest binding energy per neucleon...or is it the
> > highest, can't remember)
>
> I hate it when I have to dive into thick books
> more
> suited for anchors than reading but here goes...
>
> Not all stars form iron. The one thing that
> determines
> the entire life of a star is how fat it is. An
> anorexic "star"
> is just another Jupiter or Super-Jupiter. At
> somewhere
> around 12-13 times the mass of Jupiter, a star
> starts to
> burn deuterium and we can really call it a star.
>
> Stars "burn" hydrogen. Deuterium is just regular
> hydrogen toting a neutron in its backpack. Slap two
> of them together and you get helium (and a lot of
> excess
> energy). All stars, regardless of size, start out as
> hydrogen
> burners. The D-D chain is the easiest reaction to
> get
> started but there are lots of routes from hydrogen
> to
> helium that use other elements for their
> intermediate
> stages (called proton-proton reactions) and I'm not
> going to type them all out. So there.
>
> Fast forward a few billion years. A star will
> use up
> all of its hydrogen. About the time it's running on
> fumes,
> the helium "ash" left over from burning up all your
> hydrogen
> like there was no tomorrow has sunk to the core and
> is
> getting hotter and denser. Eventually, that helium
> in the
> core starts to burn. Now, the star is a
> helium-burner.
>
> This nuclear heat generated in the
> helium-burning core
> causes the star to expand and expand and expand into
> a big gasball many times its original size: a red
> giant.
> A star has to be at least half the mass of our Sun
> to do
> this. Our Sun will do this... in another 4-5 billion
> years.
> Goodbye, Solar System.
>
> A helium burner this big will evolve
> carbon12-burning.
> Again there are many possible reactions, but most of
> the carbon is turned directly into oxygen16. As
> things get
> hotter, we get neon20, magnesium24, silicon28, each
> one
> is produced by slapping ("fusing") a helium nucleus
> into
> the last one, hence the jump by 4, 4, 4, 4...
>
> Now, a nice little star like our Sun will just
> end up as
> a bright superdense carbon12 diamond a few thousand
> miles across, called a white dwarf. But if the mass
> of a
> star is 1.4 times the mass of the Sun or greater, it
> will
> just go crazy with this fusion stuff. The end result
> is a
> star with an "onion" structure: an outer shell of
> hydrogen
> burning surrounding a shell of helium burning,
> surrounding
> a shell of carbon burning, surrounding a shell of
> neon
> burning, surrounding a shell of oxygen burning,
> surrounding
> a shell of silicon burning, surrounding a core where
> the
> really weird stuff goes on.
>
> Silicon burning should proceed until iron is
> built, but
> it doesn't happen. By this time the heat, pressure
> and
> energies involved are so great that the LIGHT
> produced
> by the fusion becomes more powerful and energetic
> than
> all the other players! As soon as a nuclei heavier
> than silicon
> is produced, a photon on steroids knocks it apart,
> slaps
> it down, and kicks it around until it gives up those
> extra
> nucleons and crawls off in all its silicon
> shabbiness. Iron
> may get formed but it doesn't last.
>
> And, yes, iron has the HIGHEST binding energy
> per
> nucleon and a high electric charge barrier, but the
> real
> problem is that the photons produced by creating it
> are
> energetic enough to rip it apart. If you want to
> picture the
> true violence of a stellar interior, try imagining a
> beam of
> light powerful enough to smash atoms... OK, they're
> super-gamma rays, but they're still just light.
>
> The iron (and nickel) core forms inside the
> silicon
> burning shell as some of the iron continually being
> formed
> escapes from the cycle of birth and instant
> photo-death
> by "dripping" down out of sight in the core as it
> forms.
> But the iron core is doomed. Eventually the mass and
> pressure
> of the star's outer layers collapse the core and
> compress
> it so much that the star crushes its own core hard
> enough
> to "squeeze" the electrons in its atoms into the
> protons in
> those atoms and turn them into neutrons. The body of
> the
> star is blown away and there's a 20-mile lump of
> neutrons
> left behind, almost pure "neutronium" with a thin
> crust of
> hot diamond and some silicon, perhaps.
>
> This is how a universe that started out as
> nothing but
> hydrogen, helium, and a smidge of deuterium got so
> interesting, because core collapse triggers those
> nasty
> supernovae. Supernovae come in two varieties:
> Regular
> Really Nasty, and Extra Special Super Nasty,
> sometimes
> boringly called Type I and Type II. The supernova
> explosion is triggered by the collapse of the iron
> core ("I
> just can't take it any more!")
>
> Oddly, core collapse is very, very orderly*, not
> the mad
> chaos you'd think would happen, not at all. Entropy
> is constant
> and the core is in perfect equilibrium the whole
> milliseconds long
> duration of its collapse. Collapse starts when the
> core reaches a
> density of about 1,000,000,000 gm/cm3. Nothing can
> stop the
> collapse until the density reaches
> 270,000,000,000,000 gm/cm3
> when the core is now one immense elemental particle,
> a single nucleon
> miles across, at zero internal pressure, having
> achieved its true
> happiness as a particle. Unfortunately, momentum
> wants it
> to try to collapse further; it fails, and the core
> bounces back.
>
> The mild slap of its rebound will knock 10 or
> 100 solar masses
> of star away at a goodly fraction of the speed of
> light, releasing
> 100,000,000,000,000,000,000,000,000,000,000,000,000
> ergs of
> energy, a mere 1% of the core's rebound force. The
> Regular
> Really Nasty supernova core remains behind as a
> neutron star,
> and the Extra Special Super Nasty supernova core
> retreats
> from the universe altogether, becoming a Black Hole.
> It all
> depends on the mass of the star.
> ( * New study on "orderly" supernova:
>
http://www.space.com/scienceastronomy/061026_exploding_star.html)
>
> So how do we get all the elements heavier than
> iron? Not
> directly by fusion of lighter elements; that can't
> happen. No,
> it's by two processes that go on in the exotic
> environment of
> big energetic stars. There's always plenty of
> neutrons hanging
> around in such places. A nucleus swallows a neutron,
> spits up
> an electron ("beta-decay"), and advances one square
> to the
> next isotope on the game board.
>
> But all nuclei are different; some will
> transform rapidly
> ("r-process"); some will only do it slowly
> ("s-process").
> There are 27 isotopes that the r-process can't
> produce, but
> the s-process can, blah, blah. Somehow they all get
> made,
> most of them in the final short time before the
> star's death.
> Oddly enough for something so huge, stars are
> remarkably
> alike, and the mixture of elements in most stars is
> very much
> like our Sun's (the "cosmic abundances").
>
> Ed raised the question of dating the age of the
> actual
> elements themselves. Originally, hydrogen is the
> great
> grand-daddy of elements, along with some of the
> helium.
> Everything else is made in stars. If the universe
> started out
> with only hydrogen and helium, the earliest stars
> would not
> have had anything else in them. No stellar process
> makes hydrogen
> atoms, so almost all the hydrogen you meet (like the
> hydrogen
> walking around in its disguise as a fellow human
> being) is as
> old as the Universe itself!
>
> The lifetime of a star depends entirely on its
> mass and
> almost nothing else. The heaviest known star is HD
> 93250
> at 120 solar masses. It'll be gone in a few years
> (its lifetime
> is about 600,000 to 700,000 years). On the other
> hand, a tiny
> 0.10 solar mass red dwarf will last about 10
> trillion years!
> (Lifetime = ( 1 / SolMasses^(K-1) ) * 10^10 years,
> where
> K is 3 for big stars and 4 for small stars)
>
> When a star novasplodes, it blows a mix of
> elements
> out as the gas and dust from which new stars will be
> made.
> Later stars will start out as a mix of elements and
> make
> more. The newest stars should have a richer mix of
> elements
> than our old Sun. And this is what we find: old red
> dwarves
> that are mostly hydrogen and wildly metal-rich new
> stars
> and everything inbetween.
>
> The age of the actual elements? Why, they're
> still being
> made today! And some are nearly as old as the
> universe.
> Which, BTW, is 13.7 +/- 0.5 billion years old.
> Judging the age
> and mix of all the elements, our Milky Way Galaxy
> calculates
> as 10.16 billion years old, our solar system
> (planets) as 4.6
> billion (with the Sun about 160 million years
> older). Using
> other measures, globular clusters, the oldest
> groupings of
> stars, seem to be 11 billion years old based on
> their mix
> of age and size of stars.
>
> But when the researchers teased a few atoms of
> iron60
> out of the Pacific mud from only 2.5 million years
> ago, those
> atoms were "made" from scratch in some supernova
> less than
> 5 million years ago. So, while you and your hydrogen
> atoms
> are venerable and ancient, your car is made of
> younger stuff...
> Even if it is 5 billion years old. (Time to trade it
> in!)
>
> As for chondrules (at last!), the theories are
> many, the
> facts are few. The theories of their origin are: by
> impact
> melting from very early planetesimals, the product
> of a very
> hot inner solar nebula, by ablation of small
> objects, by an
> energetic outburst of the Sun, by bipolar solar
> outflows,
> by magnetic flares, by nebular lightening, by shock
> waves
> in accretion or some other nebular process, or by
> shock from
> a nearby supernova. Lots of theories to choose from
> (limit
> three to a customer).
>
> I think Derek Sears' theory is clever and
> well-thought-out
> and ingenious and probably wrong. He supposes that
> the
> resonant orbits from which the Earth receives its
> many
> chondrites are wall-to-wall with condrite parent
> bodies, that
> these bodies are the ONLY chondrite bodies there
> are, that
> they are few and rare, that Earth's meteorite
> population is
> specific and unique, that chondrules and their
> accreted
> chondrites were a rare and unique by-product of the
> early
> solar system and not representative of early solar
> materials
> at all. In other words, aren't we special...?
>
> Very narrow zones of unique chondrite parent
> bodies
> implies both an early solar system and a present
> asteroid
> belt that is very tightly zoned. In other words, the
> Earthly
> prevalence of chondrites would just be a
> coincidence.
> The evidence is that the asteroid belt is a gumbo,
> though,
> full of all sorts of things that "don't belong"
> there. The
> failure to find obvious sources for chondrites in
> the asteroid
> belt is one of the great nagging problems that has
> never
> been answered well, so he may have something. I'm
> just
> not sure what.
>
> Sears says one advantage of the theory is that
> otherwise
> the energy required to flash melt a solar system
> full of
> chondrules is a major fraction of the total energy
> available.
> Of course a precursor supernova that melted them
> would
> take care of that problem, too. Supernovae have a
> way of
> making short work of both problems and non-problems
> alike!
> The nearest short-term supernova candidate is HR8210
> or
> IK Pegasi, which is incomfortably close at 150 light
> years.
>
http://www.eso.org/outreach/eduoff/edu-prog/catchastar/casreports-2004/rep-310/
> and
> http://www.newscientist.com/article.ns?id=dn2311
> Of course, it could take millions of years to go
> super,
> or it could happen in 10,000 years, or it could
> start up
> tomorrow.
>
> That's what makes life so interesting.
>
>
> Sterling K. Webb
>
-----------------------------------------------------------------------
> ----- Original Message -----
> From: "Rob McCafferty" <rob_mccafferty_at_yahoo.com>
> To: "Pete Pete" <rsvp321_at_hotmail.com>;
> <meteorite-list_at_meteoritecentral.com>
> Sent: Wednesday, October 25, 2006 2:52 PM
> Subject: RE: Re : [meteorite-list] Chondrule
> formation mechanism (Info
> Please)
>
>
> >I suppose you are correct. I suspect the iron
> flecks
> > in chondrites must be stellar relics.
> >
> > The iron is formed in the cores of all stars.
> > Nuclearly speaking it is the stablest of all
> elements
> > (lowest binding energy per neucleon...or is it the
> > highest, can't remember)
> > So as a consequence it is the final fusion product
> in
> > the cores of all stars which are heavy enough to
> get
> > that far (red dwarf stars aren't considered
> massive
> > enough to get beyond the helium burning phase).
> > However, only supernovae spread their innards out
> at
> > the end so every atom of iron was created by a
> > supernova as indeed was every atom that isn't
> > hydrogen, helium or lithium. All others are
> created in
> > stars. However, the atoms higher in the periodic
> table
> > cannot be made in stars as they require a net
> input of
> > energy to fuse whereas the lighter ones relase
> energy.
> > Only in a huge energy surplus can you manufacture
> > these higher elements. This is where the supernova
> > comes in. In that brief period where the star
> > aoutshines an entire galaxy, there is enough
> excess
> > energy to create quantities of elements up to
> Uranium
> > (and possibly beyond but non of these are stable).
> > This is a most wonderful process which not only
> > creates all the elements needed for life but also
> > seeds the universe with them.
> > And not a crackpot creationist theory involving
> > venting asteroids into space in sight.
> >
> > As for the ages of the iron/nickel. I'm not sure
> if
> > ages are measured or if they can be. That'd be
> > interesting if they could. It's probable that our
> sun
> > and solar system are not even second or third
> > generation. The big stars last only a short period
> and
> > there's been a long time for the cycle to repeat a
> few
> > times.
> >
> > Rob McC
> >
> > --- Pete Pete <rsvp321_at_hotmail.com> wrote:
> >
> >> Hi, all,
> >>
> >> This discussion about chondrules is fascinating!
> >>
> >> Hoping not to digress off this topic too much,
> but a
> >> question I have is
> >> about the metal flecks (not the later-formed iron
> >> meteorites) in any of the
> >> stonies.
> >>
> >> Have they ever been given an estimated age?
> >>
> >> If the heavy elements, such as nickel and iron,
> are
> >> created by a supernova,
> >> and the chondrules are in theory formed much
> later
> >> during the future
> >> dynamics of our solar system's nebula, would it
> be
> >> fair to say that the
> >> metal flecks would be billions and billions
> >> (apologies, Carl) of years OLDER
> >> than chondrules?
> >>
> >> And that they came from a distance much further
> than
> >> our solar system's
> >> vicinity?
> >>
> >> Considering that the supernova is exploding
> outward
> >> and the new elements'
> >> density is thinning out very quickly, wouldn't it
> be
> >> more likely that these
> >> iron and nickel flecks that eventually found a
> new
> >> home in our solar nebula
> >> and meteorites have come from more than one,
> >> probably a lot more, supernova?
> >>
> >> If so, why don't we see any remnants of any
> >> supernova explosion in our
> >> relative proximity? The Helix Nebula is the
> closest
> >> to us, at 450
> >> light-years!
> >>
> >
>
http://images.google.ca/images?q=helix+nebula&hl=en&lr=&sa=X&oi=images&ct=title
> >>
> >> Not even a wisp left...
> >> Are tiny, but very dense, nebulas even possible?
> I
> >> can't imagine dust-bunny
> >> nebulae.
> >>
> >> If not, would it be unreasonable to expect that
> our
> >> planetary nebula could
> >> have extended out to Centauri, where our closest
> >> star neighbours are?
> >> When I dwell on the "Pillars of Creation" photos
> >> (Orion stellar-formation nebula,
> >>
> >
>
http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/44/image/a)
> >>
> >> that describes a small point being comparable to
> the
> >> breadth of our solar
> >> system, ~4.3 light-years to Centauri isn't that
> >> far...
> >>
> >> Maybe the seldom-discussed/appreciated metal
> flecks
> >> are the real gems in the
> >> meteorites?
> >>
> >> Or, is the nebula in my head too dense that am I
> >> just missing something
> >> obvious?
> >> How is my logic flawed?
> >>
> >> Cheers,
> >> Pete
> >>
>
>
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Received on Fri 27 Oct 2006 12:29:00 PM PDT