how old is the star that created earth?

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Offline mcjhn

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how old is the star that created earth?
« on: 20/11/2010 02:52:38 »
one of my lecturers made the hypothesis that if U(235) and U(238) were created in the same relative abundance in supernova (which he said is quite a good assumption) you could extrapolate back to estimate when the star we are all made of exploded (and a lower bound to the age of the universe).

does this look correct? you can solve the equations algebraically but I'm a bit rusty so I just made a spreadsheet, does 8.5 to 9 billion years ago sound about right?

https://spreadsheets.google.com/ccc?key=0AntR1lCmF5GLdDc5Qnk4bV9LZHdGdlRkSG5ZRDh4Z2c&hl=en

is the earth is mainly comprised of one old star or is that a bad assumption?

I was totally amazed when he told us, and I still am, I hope there's some truth in it. Thanks.

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Offline Geezer

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how old is the star that created earth?
« Reply #1 on: 20/11/2010 06:42:04 »
I'm not sure about the particular numbers, but it seems quite plausible.

The Earth has a finite existence, and the matter of which the Earth is composed was manufactured in at least one star.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline granpa

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how old is the star that created earth?
« Reply #2 on: 20/11/2010 13:41:05 »
stars that go supernova go through their lifetimes very quickly so it probably only existed for a short time just before the solar system formed.

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Offline mcjhn

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how old is the star that created earth?
« Reply #3 on: 20/11/2010 14:27:08 »
I was thinking the same thing, I double checked everything and discovered I got the relative abundances mixed up.

does 5.8 - 6 billion yrs ago sound better?

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Offline granpa

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how old is the star that created earth?
« Reply #4 on: 20/11/2010 14:59:45 »
to end as a supernova a star must start with at least 9 solar masses.
a star of 10 solar masses has a lifetime of 30,000,000 years.

http://en.wikipedia.org/wiki/Type_II_supernova
http://www.astronomynotes.com/evolutn/s2.htm

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Offline Geezer

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how old is the star that created earth?
« Reply #5 on: 21/11/2010 05:24:15 »
to end as a supernova a star must start with at least 9 solar masses.
a star of 10 solar masses has a lifetime of 30,000,000 years.

http://en.wikipedia.org/wiki/Type_II_supernova
http://www.astronomynotes.com/evolutn/s2.htm

Wow! In the grand scheme of things, that's a short life.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.