# Cosmic Guru's - Do we know how many "generations" old the Universe is? **URL:** \ **Category:** Factual Questions\ **Created:** [February 11, 2003, 4:31pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364 "2003-02-11T16:31:57Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![bernse](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@bernse](https://boards.straightdope.com/u/bernse)\ **Post date:** [February 11, 2003, 4:31pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364/1 "2003-02-11T16:31:57Z")
Correct me on any incorrect assumptions! It’s my understanding that the best guess of the age of the Universe is _around_ 15 billion years old. It is also my understanding that new stars/planet systems formed from the leftovers of old stars. I am _assuming_ (actually, I think I recall reading somewhere in my youth) that this is where _heavier_ elements come from… leftovers from Stars. So, if the Earth and our Sol system is _around_ 5 billion years old, is it a safe _assumption_ that there has been _roughly_ 3 generations of stars since the Big-Bang? Are any of the original stars that were first formed around the big bang still around or are they all long gone? Can a star last for the say, 15 billion years since the beginning of time? Or, did the universe have to “cool” for a few billion years after the BB before stars could even _form_ in the first place? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [February 11, 2003, 4:49pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364/2 "2003-02-11T16:49:08Z")
In general, the larger a star is, the shorter it lives. No doubt there are white dwarf stars out there that have been happily simmering away since shortly after the big bang, when the first stars formed. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [February 11, 2003, 4:54pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364/3 "2003-02-11T16:54:16Z")
**Q.E.D.** is correct. The bigger the star the shorter its life. The really big ones have lifespans measured in ‘mere’ millions of years. Our sun by comparison should go for around 10 billion years. The very early universe was likely populated by massive suns almost exclusively. Everything was closer together then so they had much more available hydrogen to form from making for very big stars. That said there is a lot of time in between a star going nova and another star reforming so in the end I think your guess is correct that our sun is a third or fourth generation star and you and I are made of stuff that has been in three or four other stars in the past. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [February 11, 2003, 5:08pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364/4 "2003-02-11T17:08:41Z")
At the very least, the Sun has to be second-generation star, since many of the elements of which we and the earth are composed can only form in the fiery furnace of a supernova. Fusion in ordinary stars stops at carbon, and even very large stars can only form elements as heavy as iron during their normal lifespan. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [February 11, 2003, 5:13pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364/5 "2003-02-11T17:13:00Z")
[Atom : An Odyssey from the Big Bang to Life on Earth…and Beyond, by Lawrence M. Krauss](http://www.amazon.com/exec/obidos/tg/detail/-/0316499463/qid=1044983456/sr=8-1/ref=sr_8_1/103-3312852-0368660?v=glance&s=books&n=507846) tries to follow the journey a few atoms take from the beginning of the universe to present day Earth, including their stay in various earlier generation star systems. It’s exactly what you want to read to answer your question. ---
**Author:** ![bernse](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@bernse](https://boards.straightdope.com/u/bernse)\ **Post date:** [February 11, 2003, 7:34pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364/6 "2003-02-11T19:34:15Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > \*\*In general, the larger a star is, the shorter it lives. No doubt there are white dwarf stars out there that have been happily simmering away since shortly after the big bang, when the first stars formed. \*\* Have we found any? Do we know they are “Generation 1” stars? How can we tell? Elemental make-up? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [February 11, 2003, 7:54pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364/7 "2003-02-11T19:54:11Z")
The stars mentioned [here](http://hubblesite.org/newscenter/archive/2002/10/) are most likely first generation. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [February 11, 2003, 7:56pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364/8 "2003-02-11T19:56:06Z")
The first stars to form contained very little besides hydrogen and helium. Later generations of stars contain metals derived from the explosion of the first generation. Perversely, those early metal poor stars are called “population two”, while the newer metal rich stars are called “population one”. [Stellar Populations](http://www.astro.umd.edu/education/astro/mw/pop.html) ---
**Author:** ![bernse](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@bernse](https://boards.straightdope.com/u/bernse)\ **Post date:** [February 11, 2003, 8:45pm UTC](https://boards.straightdope.com/t/cosmic-gurus-do-we-know-how-many-generations-old-the-universe-is/154364/9 "2003-02-11T20:45:19Z")
Thanks for the info. It turns out there are “Population III” stars as well, which are even earlier. The little bit of snooping I have done so far (admitidly, not much) doesn’t show any “proof” of them yet (or at least, not that I’ve found). I found this from: [http://www.solstation.com/x-objects/first.htm](http://www.solstation.com/x-objects/first.htm) > [@](#): > > However, the existence of HE 0107-5240 suggests that there must be other ways of achieving the necessary cooling. Moreover, the star’s discovery suggests to some astronomers that even relatively low-mass Population III stars could have formed and survived until today, still shining faintly below easy detectability as main sequence dwarf stars in distant reaches of the galactic halo. So, if I understand that correctly, its _possible_ that there could be some surviving stars to this day but doesn’t look like they’ve found any for sure.