What evidence is there to suggest that the sun was formed from material produced when an earlier star exploded?

Answer 1

This was on Yahoo answers (http://answers.yahoo.com/question/index?qid=20071228163233AAI0621) and explains quite well why our sun is second generation at least:

The only elements that would have been formed from the big bang are hydrogen, helium, and perhaps trace amounts of lithium. Elements up to iron can be produced in a star by nuclear fusion. (Heavier elements require more energy to start the fusion than is released in the fusion reaction--i.e. energy is LOST. Therefore, only elements up to iron are formed by nuclear fusion.) In a star like our sun, there is not enough mass to create the pressure and heat needed for even the fusion into iron. Our sun will produce metals only up to carbon and oxygen.

Any metals heaver than iron could only be produced in a supernova. (Just a note, astronomers and astrophysics use the term "metal" to mean any element heaver than hydrogen or helium).

The fact that our sun contains trace amounts of iron and heavier metals means it must have been there when it formed, since these cannot be formed by the nuclear fusion within our sun. Since first generation stars would only contain hydrogen, helium, and trace amounts of lithium from the big bang, our sun is not a first generation.

This makes sense since our sun is only around 5 billion years old and the universe is about 16 billion (opinion varies from 11 to 20 billion, but 16 is right in there and generally accepted). That leaves at least 10 billion year for things to have happen before our sun formed: That is a lot of years for other stars to have formed and died, recycling some of its mass back into the universe and our sun. Since the life cycle of very large stars could be as little as 100 million years to supernova stage, the sun could conceivably be many generations along.

Anyway you look at it, it is definitely AT LEAST second generation.