Star ages/lifetimes/generations

[hkyriazi]

Given that a star's lifetime depends significantly upon its initial mass, do we really know what generation the sun is? I'd always assumed it was 2nd (or 3rd) generation, being derived from the exploded remnant of a 1st or 2nd generation star, but given the possible large variability in ages of stars, I'm no longer sure about that assumption. I understand the grouping into Population I (such as the sun), Population II, and the hypothetical, very short-lived Population III (or have we actually seen some of these at the edge of our observable universe?). Another way of asking the question is, does the metallicity of Population I stars vary greatly, such that some may have been created from the remains of others?

 

[stefan r]

...does the metallicity of Population I stars vary greatly, such that some may have been created from the remains of others?

The Milky Way's thin disc formed long before the Sun formed. The thin disc contains elements that would have formed in neutron star mergers.
After the thin disc formed stars continued to explode and add material. The shock waves in a gas cloud formed the Sun and solar system.

I do not know what the upper limit is on the number of stars an atom could have been part of. A significant fraction would have been in a population 1 star before finding it's way to the sun. Some of the hydrogen and helium would have never been in a star.

There is variability in stellar metalicity. The cloud is mixed.

 

[hkyriazi]

What I'm actually concerned with--and perhaps I should've considered this before my original post--is whether we have a solid idea of the ages of the various stars, such as to independently confirm the age of the universe calculated on the basis of the redshift/distance relationship (Hubble Constant, etc.). In other words, does our knowledge of stellar evolution, and associated nuclear and nucleosynthetic reactions, allow us to affix an age to the Universe since the "Big Bang"?

 

[phyzguy]

It is possible to determine the age of individual stars, but the best way to do what you are asking is to work with clusters of stars. This website explains the technique. By plotting the HR diagram of a cluster, we can determine the age of the cluster by looking at the most massive stars which are still on the main sequence. This paper shows a recent estimate of the ages of the oldest known clusters. They appear to be a little more than 11 Gy old, which is consistent with the age of the universe calculated from the Cosmic Microwave Background (CMB), which gives an age of the universe of a little more than 13 Gy. It took some time after the Big Bang before the universe cooled and "clumped" enough for stars to begin to form. The time after the decoupling of the CMB and before the formation of the first stars is often referred to as the "Dark Ages".

 

[Vanadium 50]

In other words, does our knowledge of stellar evolution, and associated nuclear and nucleosynthetic reactions, allow us to affix an age to the Universe since the "Big Bang"?

No. All you know is that the universe can be no younger than it's oldest known star. In fact, the very oldest known stars are about half a billion years younger than the universe as a whole.

 

[hkyriazi]

No. All you know is that the universe can be no younger than it's oldest known star. In fact, the very oldest known stars are about half a billion years younger than the universe as a whole.

Thanks. I should have said "...allow us roughly to affix an age to the Universe since the "Big Bang"..."

I found some recent links from a google search for "oldest stars," including this: http://www.astronomy.com/news/2018/11/red-dwarf-is-one-of-the-oldest-in-the-universe
I assume this is what you were referring to. Interesting that this seems to not have formed from the remnants of hypothesized, short-lived "Population III" stars.

 

[hkyriazi]

It is possible to determine the age of individual stars, but the best way to do what you are asking is to work with clusters of stars. This website explains the technique. By plotting the HR diagram of a cluster, we can determine the age of the cluster by looking at the most massive stars which are still on the main sequence. This paper shows a recent estimate of the ages of the oldest known clusters. ...

Thank you! The University of Oregon website, though somewhat sketchy (and assuming a solid background in astrophysics), gave the basic idea (and seemed to be written by a non-native English speaker). The review by Lawrence Krauss (and Chaboyer) is much appreciated, as it covers the entire "age estimate of the universe" thoroughly. Nice that it was freely downloadable.