How old could population I stars theoretically be? What's the earliest they could have formed?

  • $\begingroup$ Are you referring to the third generation of stars that formed, or Population III stars, which formed first? $\endgroup$ – HDE 226868 Nov 7 '18 at 15:17
  • $\begingroup$ No, generation three. I believe third generation stars (I believe pop I stars) are necessary for the formation of life. I wanted a theoretical limit to earliest life could form in universe. A rough estimate obviously. In addition to the earliest, what time in general did these highly metallic stars start to form? $\endgroup$ – Jimmy G. Nov 7 '18 at 17:25
  • $\begingroup$ I'm not familiar with this "generation" terminology. As the wiki article I reference states, it's very plausible that there was a habitable epoch, between about 10 to 17 million years after the Big Bang, during which life could plausibly arise. This is argued by Loeb at Harvard. See here, en.wikipedia.org/wiki/… $\endgroup$ – N. Steinle Nov 7 '18 at 18:35
  • $\begingroup$ The Sun can indeed be termed a "third generation star". It contains elements that have been in at least two other stars. See astronomy.stackexchange.com/questions/16311/… $\endgroup$ – Rob Jeffries Nov 14 '18 at 14:03
  • $\begingroup$ Population I though is not quite the same thing. It refers to a set of chemical and kinematic characteristics whose definition is not particularly rigid. $\endgroup$ – Rob Jeffries Nov 14 '18 at 14:04

Since Pop III stars are the oldest stars, then they could have theoretically began to form in the Cosmic Dark Age (CDA), see section 5, since the oldest galaxy we've observed so far (in infrared) is about half way through the CDA (~$480$ million years). As the article states,

Stars and galaxies are formed when dense regions of gas form due to the action of gravity, and this takes a long time within a near-uniform density of gas and on the scale required, so it is estimated that stars did not exist for perhaps hundreds of millions of years after recombination.

So not only must the temperature of the universe be sufficiently cool, gravity must have acted for a long enough amount of time for baryonic structure to begin to form.

| improve this answer | |
  • 1
    $\begingroup$ Not Pop III, gen III. $\endgroup$ – Jimmy G. Nov 7 '18 at 17:20
  • $\begingroup$ What is "gen III" ? $\endgroup$ – N. Steinle Nov 7 '18 at 18:41
  • $\begingroup$ The more I look, the more it seems like this is a popular, not scientific term. I am going to change the question, I want to know howe early Pop I stars could form. $\endgroup$ – Jimmy G. Nov 14 '18 at 1:21
  • $\begingroup$ @JimmyG. Your terminology is fine. The Sun is a "third generation" population I star. $\endgroup$ – Rob Jeffries Nov 14 '18 at 14:01
  • $\begingroup$ Can someone please provide a reference for such terminology? $\endgroup$ – N. Steinle Nov 14 '18 at 16:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.