Oldest known star?

A freewheeling astro-salon.

Oldest known star?

Postby cheryl-lane » Wed Feb 12, 2014 10:06 am

Can someone please explain how, as reported in the news recently, the "oldest known star in the universe" is only 6,000 light years away from earth? Thanks.
User avatar
cheryl-lane
 
Posts: 1
Joined: Thu Apr 11, 2013 10:22 am

Re: Oldest known star?

Postby rene-gedaly » Wed Feb 12, 2014 3:29 pm

Yeah, I saw that, too, and scratched my head. But my guess is that this isn't the furthest away star from us, in fact it isn't, just the oldest found. So at 6000 ly from us, that puts it in our galaxy (yikes, I think! interestingly, this oldest observed star would then be older than our galaxy...) and if you know about the Hertzprung Russel diagram, the star is probably one of those "red dwarfs" that lives forever. At our last general meeting, Professor Reggie Dufour spoke about it (not the star, the HR diagram). It'll be interesting to see how this story develops.
Rene Scandone Gedaly, Forum Moderator
Membership, Texas 45-Visual, Observatory Trainer, Past Prez
User avatar
rene-gedaly
 
Posts: 487
Joined: Tue Feb 14, 2012 1:30 pm

Re: Oldest known star?

Postby bill-pellerin » Wed Feb 12, 2014 4:20 pm

The key idea here is the oldest known star. That is, of the stars for which we have good enough data to determine the star's age, this would be the oldest. The very low mass stars at the bottom right of the HR diagram (brown dwarf stars) have have lifetime longer than the current age of the universe. They are burning so slowly that they haven't used up all their hydrogen yet.

So, the issue in determining the 'oldest' is not figuring out which one has lived the longest (then died), it's about which star that's still alive turned on the earliest. I expect it would be very difficult to determine which one of a large population of early stars turned on the earliest. It seems unlikely to me that the ability to determine that with significant precision would limit our ability to determine which is the oldest star. Perhaps the star that's being talked about as the 'oldest' is the one for which there is agreement that it turned on earlier than all the others for which we have a predicted turn-on time.

White dwarf stars (for those who think these objects should still be called stars -- since they're not lit by nuclear fusion but by residual heat) have not had enough time in the universe to cool down to their final stage -- a black dwarf. Are any of these candidates for the oldest star?
User avatar
bill-pellerin
 
Posts: 23
Joined: Tue Feb 14, 2012 8:29 am

Re: Oldest known star?

Postby rene-gedaly » Wed Feb 12, 2014 4:34 pm

Just occurred to me that the question, other than stage of life, may be why such an old star is so close to us. I'll be watching the usual media sources for updates.
Rene Scandone Gedaly, Forum Moderator
Membership, Texas 45-Visual, Observatory Trainer, Past Prez
User avatar
rene-gedaly
 
Posts: 487
Joined: Tue Feb 14, 2012 1:30 pm

Re: Oldest known star?

Postby john-haynes » Wed Feb 12, 2014 5:18 pm

I read something about this and my understanding is that they determined the age due to a multitude of factors, but particularly through "metalicity."

In astronomy, we have a peculiar way of defining "metal." Anything that isn't hydrogen or helium is considered a 'metal.' Metalicity is the ratio of such "metals" in a given star. According to prevailing theories, after the big bang, before the first stars formed, the matter (at least baryonic matter, i.e. not dark matter), was nearly entirely hydrogen with some helium and traces lf lithium and beryllium (the four lightest elments). All other elements were then created in the first stars or in their supernovae. Thus, the very oldest stars would have had low metalicity.

This star was found wandering the Milky Way and when astronomers analyzed its spectrum, they found little or no evidence of absorbtion lines for other metals. Thus, the star was created in one of the first generations of stars in the Milky Way, within a few hundred million years of the big bang.

I say first generations, not generation, as some of the first stars were very likely very masssive and very short-lived. They began the process of creating heavier elements, blew apart and seeded the interstellar medium with gas and dust with a slightly higher metalicity, and that gas was collected into new stars. This star was likely not one of the first generation, but likely soon therafter.

As for how it got to be so close... It's possible the Milky Way itself began that early. It's also possible that the star was captured from another galaxy. We know, or think we know, that galaxies are canibals. We are in the process of ripping up and absorbing at least one other dwarf galaxy (there are theories that suggest that globular clusters are the remnants of the cores of galaxies we've absorbed). It could easilly have been formed long ago in another galaxy and swallowed up by our own. As it orbits our central black hole, it wanders and eventualy has come to be close to us - for the time being.

In all likelihood there are plenty of older stars in our galaxy, we just haven't identified them yet out of the several hundred billion stars in our neighborhood.
_________________________________
Clear Skies!

My gear:
Meade 2080 8" SCT OTA
Brandon Vernonscope 82mm f/3.7 refractor
Meade DS-2000 90mm f/11 refractor
iOptron iEQ45 Mount
SBIG STF-8300C
Canon 350D (Astro-modded)
User avatar
john-haynes
 
Posts: 64
Joined: Tue Feb 14, 2012 7:53 am

Re: Oldest known star?

Postby kim-wiley » Thu Feb 13, 2014 9:27 am

Whenever I read any new discovery, "farthest galaxy", "oldest star in the universe", I try to remember that those discoveries are truths as we know them today. It makes it no less exciting! I believe the scientific community as a whole accepts that our truths are always evolving as we continue to learn and discover. This star is the oldest star known to us today. The fact that it is in our galaxy is amazing, and I can't wait for the next discovery.
kim-wiley
 
Posts: 2
Joined: Fri May 25, 2012 4:25 pm


Return to Space Station V (the Lounge)

Who is online

Users browsing this forum: No registered users and 5 guests

cron