Straight Hate

I'm a bit apprehensive to wasting space by posting this thread, but I have a couple of questions for anyone who might care to answer them.

Our solar system, comprised of the sun, several planets, more moons and other associated debris is generally held to be made form the rememnants of an earlier star, correct? If so, is there any possibility that this star's system was home to intelligent life? Was the universe at this stage even capable of forming life, or were the heavier elements necessary for life as we know formed after this period? I find the above idea very intriguing, but have been able to find little information on the subject.

Coragyps

Hmmm... a very interesting line of thought. A couple of factors that I think need to be factored in:

The Solar System was likely formed from a molecular cloud that was "shocked" into collapsing, maybe by a supernova. A star big enough to supernova has to be pretty massive and therefore short-lived, so I wouldn't think one destined for explosion would be a real good candidate for having life around it. But a supernova is also the only place where you can form the heavier elements and get them spread through space.
The molecular cloud, though, had to come from somewhere, and that somewhere could include both primordial hydrogen and helium, and also residue from stars that had gone through red giant and planetary nebula stages. These can shed nitrogen, oxygen, carbon, etc., so they could contribute to you and me. And garden-variety stars can go down the RG/PN track, so there could potentially have been some with planets that vaporized to make our cloud. So it might not be all that impossible: the question would come down to whether there was enough time from the birth of the universe to the birth of the solar system to squeeze in enough generations of stars with planets. Currently, maybe 1% of solar-type stars are thought to have (big) planets, and it's pure speculation how many have scrawny ones like Earth.
So my guess is that we might be partly recycled alien, but not with real high liklihood. But then, I mostly look at stars, and don't study them professionally.

Asha'man

An interesting question...I'll give it a try.

Earlier star? I’m not sure what the theory is that you have heard, but it doesn’t sound quite right. More like thousands of earlier stars.

Our solar system contains materials from several generations of earlier stars, all of which exploded at the end of their lifetime. All elements heavier than Iron are created in supernovas, and everything heavier than hydrogen is formed in the nuclear furnace of a star’s interior. Since we have an abundance of material on Earth that is heavier than hydrogen, all of this must have come from other stars that exploded. Lots of them.

When a star explodes into a supernova, it releases a cloud of gas and dust that spreads out across the galaxy. Eventually, the dust and gas from multiple explosions, mixed with the already abundant hydrogen, starts to collapse into a denser cloud. Out of that cloud, our star and planets formed. This happened about 4.5 billion years ago.

Now, since the Universe appears to be around 14 billion years old, there are about 10 billion years to think about before our star formed. However, for much of that time, there was little more than hydrogen and helium, because the first generation of supernovas hadn’t happened yet. (The lifespan of our star is around 10 billion years. Larger stars burn faster, and only larger stars go supernova, but it still takes a billion years or so.) Any star forming in those early days wouldn’t have the heavier elements needed for life as we know it.

A star that formed a little later might have the heavy elements needed for life, but it seems that intelligent life may take 4 billion years to show up. (Statistical sample size of 1, so the error range may be a bit high on that number.) If the material from that star was incorporated into our own system, then that star must have exploded at least 5 billion years ago, and probably didn’t have time for intelligence to show up.

Doubting Didymus

Actually, no. It wouldn't neccessarily take anywhere near that long. Evolution hasn't been working towards intelligence for all that time. Its been meandering about minding everyone elses buisiness.

Granted, on this earth it took a couple of billion years to evolve multicellularity, but once that had happened, the potential for intelligence like ours was there, and it only took around 50 million years to go from a small shrewlike mammal to an intelligent ape. I think that this could have happened at any time in the last 500 million years.

I suppose the main problem then is trying to work out how long it would take to get a cell that could go multicellular. Once you have that you only need a couple of million years to get intelligence. Here on earth it took about 3 billion years, but like you said that's a sample of 1.

Deimos

Nitpick...

Big Bang theory predicts nucleosynthesis of hydrogen, helium and a pinch of lithium, if I remember correctly.

beausoleil

Just to correct a misconception being reiterated above.

A lot of the elements heavier than iron are actually made in the s-process. This takes place in the He burning zones of giant stars - not supernovae. They are recylced into the interstellar medium by stellar winds.

It's the r-process that is associated with supernovae, however.

For instance barium is mostly an s-process element, europium mostly an r-process element.

Mageth

...europium mostly an r-process element

And here I was thinking it came from French Poppies...

Asha'man

Hmm, I guess I have more reading to do. Does anyone want to provide a snap definition of the r-process and the s-process for me?

Coragyps

The amateur's definitions:
s-process is the slow process of banging neutrons or nuclei into other nuclei, with time between collisions for short-halflife products to radioactively decay.

r-process is rapid, where you can get multiple fusions with very little time between, and only the "final" product has the oppotunity to decay to a stable state. Nickel 56 is, IIRC, a good example: it largely powers the visible glow of a supernova in the weeks following the explosion, decaying to cobalt and then iron.

fando

Excellent responses so far, but I'd like to clear up one uncertainty by suggesting that there was plenty of heavy elements to form terrestrial planets early in the galaxy's history. The source is simply supermassive stars with short life spans on the order of 10s to 100s of millions of years.

Also, recall the conjecture that major evolutionary changes come in bursts. The idea is that it takes a catastrophe to accelerate evolutionary 'progress' towards more complexity. This suggests a hypothesis that in some cases, intelligent life can arise far quicker than occured here on Earth.

So I say it is certainly possible for intelligent life to exist billions of years ago. We can't just rule that out.