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How many generations

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How many generations was created by Rice

Here is a question that has puzzled me for a while.

We know the Earth is approx 6b years old and the Universe 15-16b years.
(Feel free to correct my figures I am too lazy to look them up!).

We know the elements that occur naturally on it and we also have theories suggesting the conditions that manufacture them from primorial (in a stellar sense) Hydrogen- eg Iron from nuclear fusion of a mainstream star. Heavier elements require Novae etc.

Can anyone hazzard a guess based on standard theory of stellar evolution on how many generations of stellar lives have gone into providing our current home?
ULT
14 years 9 months ago #66931

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Replied by ftodonoghue on topic Re: How many generations

I think I remember hearing that our sun is a third / fourth generation star, but couldn't be sure
Cheers
Trevor
14 years 9 months ago #66936

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Replied by jeyjey on topic Re: How many generations

I'm also under the impression that it's a fairly low number (certainly in terms of cosmology) -- but I don't have a specific figure.

-- Jeff.
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14 years 9 months ago #66939

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Replied by Seanie_Morris on topic Re: How many generations

Our Sun is definitely a second generation. As to it being any more is up for speculation based on the apparent known age of the Cosmos (13.7 billion years old). We know it is a second generation because of the make up of the other bodies around it. We have abundant elements such as heavy metals like iron, aluminium, titanium, and more in the planets and asteroids. These elements, in fact almost the periodic table above iron in weight (8 is it?) can really only be produced out of an atomic explosion like that of a supernova. So, the theory goes that the predecessor in our part of the galaxy became a supergiant, exploded when its fuel was exhausted (producing those heavy elements in the process), and from the nebula left over, our Sun formed. The rest, as they say, is history.

Seanie.
Midlands Astronomy Club.
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14 years 9 months ago #66940

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Replied by Petermark on topic Re: How many generations

Parts of the presolar material have been preserved.
Their isotopic make up is very different from the solar value indicating that they were born in a range of presolar stars.
See:
en.wikipedia.org/wiki/Presolar_grains

As for how many "generations".
As Jeff said it's a very low number but it would depend on the masses of the precursor stars.
A lot of generations of supergiants have exploded.
On the other hand the first generation of brown dwarfs is still here and will be for tens of billions of years into the future.
Mark.
Anybody who says that Earthshine is reflected Sunshine is talking Moonshine.
14 years 9 months ago #66942

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Replied by Rice on topic Thanks

Thanks to all who replied, especially Seanie and Petermark.

The reference you supplied to the Wiki entry on Pre Solar Grains was very interesting and lead me to the Nucleosynthesis entry which in summary goes something like:

300seconds after the Big Bang elements up to At No 3- Lithium form.

Stellar Fusion elements to At No 20 Calcium and At No 26 Iron

Supernovae and Fast Fusion Nickel At No 28.

Yes the suggestion that we may be on at least a second generation planet seems reasonable.
ULT
14 years 9 months ago #66979

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Replied by dmolloy on topic Re: How many generations

Makes you humble to think that not only do we live in a very big place...(the universe)...but that we are recycled carbon...second hand star dust. :(
14 years 9 months ago #67008

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Replied by phoenix on topic Re: How many generations

When I done the OU course the literature said there was three generations of stars, I, II & III. All are classified on the amount of higher atomic elements. When the course was written they had still not discovered any first generation stars which would be primarily hydrogen and helium with trace amounts of lower atomic elements. Its been 4 years since I done the course so I may not 100% correct on this and I am open to correction.
Kieran
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14 years 9 months ago #67039

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Replied by Rice on topic Type I

Thanks Phoenix,
The classification you mention makes a lot of sense.

Yes I think that recently (in the last year) the Hubble telescope had a picture of some of the earliest stars. I think now I remember it was said at the time they were sure they were among the earliest stars known- obviously that was based on their spectral composition.

This pushes us out to possibly third generation material allright.

The reason I was so interested in the issue was because of the Drake equation and a post in the SETI thread which lowered the probability of SETI's success because the communications window between civilizations would be small. Developing civilizations would rely on RF communications for only a relatively short duration (on a cosmic scale) and hence the probability of two being the RF window simultaneouly was smaller (effectively the product of P1 by P2 where both P1 and P2 are considerably less than 1).

Now given that we may be 3rd generation material and the first generation phase didn't manufacture anything heavier than Lithium then at the very least the probability of civilizations elsewhere is possibly double that given by the Drake proposition.
ULT
14 years 9 months ago #67051

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