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

From: Gerald Flaherty <grf2_at_meteoritecentral.com>
Date: Fri Oct 27 20:52:23 2006
Message-ID: <00ab01c6fa2b$434c4f10$6402a8c0_at_Dell>

I shall be forever grateful that I saved this post. Having read an exerpt of
it in Ed G's reply, I returned to the original and am forced to reiterate a
previous effusive, unabashed compliment of Sterling's effective translation
into laymans terms of the most simple of processes in the universe. Simple
in the sense of elemental.
Sterling, I hope that you can make time in your life to preserve and collect
these posts.
I for one, and I realize, I may be in the minority, find such threads more
than words like facinating can describe.
Meteorites are the glue which keeps this group together but ultimate meaning
motivates some of us to touch these sublime sources of understanding and
imagine our origins among the stars.
Who are we? Where did we come from? Where are we going?
Astrophysics, Cosmology, Chemistry, Petrology, Relativity, Sp. relativity!
Holy Cow! Hindu Metaphysics.
Jerry Flaherty
----- Original Message -----
From: "Sterling K. Webb" <sterling_k_webb_at_sbcglobal.net>
To: <meteorite-list_at_meteoritecentral.com>
Cc: "E.P. Grondine" <epgrondine_at_yahoo.com>
Sent: Friday, October 27, 2006 2:30 AM
Subject: Re: Re : [meteorite-list] Chondrule formation mechanism (Info
Please)


> 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 08:51:54 PM PDT