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(meteorobs) Archive resend Re: Murchison...10 Billion years?
Here's a corrective response to the previous posting I sent out...again from
the meteorite mailing list. The topic seems fascinating.
George
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> Hello everybody. I have read the post by Martin, and feel that I
>need to clarify some things. I will just run down the current information
>availible. This is data from the last 6 mos.,and has yet to be published.
> There are at least 4 types of interstellar grains in the
>Murchison meteorite. These are Silicon carbide, Titanium carbide,
>corundum, and Nitrogen carbide. Each type formed in
>different stars, so there are four seperate events responsible for their
>formation.
> Each grain is a product of a supernovae explosion. It is at this
>time that there is enough heat, and pressure(Enthalpy of Formation, for
>those who would like a technical term) to combine the elements to form
>the grains. These are remnents of a star that has lived through it's
>entire cycle. This is known, because silicon is the second to last
>element to by fused in a star. So, the elements had to bond after silicon
>was fused.
> The 10 billion year date comes from the fact, that, the corundum
>grains can only be fused in stars greater than 1.2 tines our Sun. The
>other grains can be fused in stars similar to the size of our Sun. This
>led to a reasoning, that went like this:If corundum can only be formed
>in a star 1.2 times the mass of our own, than(after some calculations)
>the star it originated from had to have a life cycle of at least 6 billion
>yrs.
>So the Universe had to exists for at least 6 billion yrs prior to our
>solar systems formation. Add the 4.6billion yrs of our Suns history to
>the 6 billion yrs that it took to generate the corundum grains and get an
>age of 10.6 billion yrs.
> Now, Murchison is not 10 billon yrs old, but the grains it
>contains are greater than 5 billion yrs old. Calculations for how long it
>took for those grains to travel to our neck of the woods is speculation
>at best. But, I think, it can be said that some of the grains may be on
>the order of 5.0-6.0 billon yrs, without stepping on toes. I want to be
>clear that this is speculation due to stellar distances, and not based on
>concrete evidence. Ultimately, the true age of these grains may be
>determined, but till then we can only speculate.
>
>Frank Stroik