[meteorite-list] Where all the iron and nickle came from...?

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Fri, 18 Sep 2009 11:15:52 -0500
Message-ID: <D01CC7DE72684AB1A0ED7771D7F7E842_at_ATARIENGINE2>

Hi, Mel, List,

    The recipe for a universe is simple. Start with
a batch of hot particles. Let them cool until they
combine into hydrogen atoms. As they cool, some
will fuse and make some helium.

    Now you have a universe of 75% hydrogen and
25% helium gas. Boring. Let the gas gather by gravity
into stars everywhere. More interesting. The big stars
burn fast and combine atoms bigger and bigger until
you have all the atoms up to iron, in just a few million
years.

    Then the big ones explode, creating all the elements
heavier than iron and spreading them as gas and dust
in clouds through the universe in a few billion years.
The gas and dust clump by gravity into new stars, the
biggest of which will explode in a few million years all
over again. (Some stars never learn).

    Before you know it, there's a mix of all elements
everywhere, making new stars, exploding big stars
right away. The small stars will live longer than the
universe. The medium stars will live 5 to 15 billion
years (like ours).

    We look out the window and it's still going on. We
see the remnants of the exploded stars. We see the
new stars forming. We see the young stars, the
middle-aged stars, the old stars.

    The young universe had very little heavier elements.
They increase as the universe ages. You can actually
make a good rough calculation of the age of a universe
by the amount of heavier elements you find. As the
universe gets older, the amount of heavier elements
increases.

    Iron is a particularly important element in this cycle.
It's when a star works its way up to burning iron that
it fails, collapses and goes boom! Iron is the heaviest
element that can be cooked slowly in a star; all the
heavier ones are created in the flash of the explosion.

    You see, it takes more energy to fuse iron than you
get from the fusion. Instead of heating the star, it cools
it. When the star cools, it suddenly collapses. The big
whack that results is a supernova, when all the other
elements are cooked up in an instant.

    Some (not all) believe that our star formed in a
neighborhood where there had been one or more recent
supernovae that enriched the raw materials in our star's
mix of gas and dust. It's an argument, but the evidence
seems to tilting in that direction. We keep finding traces
of isotopes from a recipe of recent exploding stars.

    So, what do you get? Five billion years later, we
get songs written especially for Woodstock that start:
"We are stardust..."


Sterling K. Webb
--------------------------------------------------------------------------
----- Original Message -----
From: "Melanie Matthews" <spacewoman2775 at hotmail.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Friday, September 18, 2009 6:05 AM
Subject: [meteorite-list] Where all the iron and nickle came from...?


>
> Hello list,
> These metallic elements are so common in stony meteorites - as we
> know... now, don't they originally form at the cores of stars, and the
> traces of these metals that contained during the earliest days of the
> formation of our Solar System, are the remnants of nearby dead stars
> that exploded millions or billions of years before the Solar System
> started to emerge?
>
> Regards
> - Mel
>
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Received on Fri 18 Sep 2009 12:15:52 PM PDT