

Nearby star is almost as old as the Universe - ananyob
http://www.nature.com/news/nearby-star-may-be-the-oldest-known-1.12196

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btilly
One question that I have about this research is whether it is possible that
the star could have picked up heavier elements in unexpected ways. Sure, the
amount of heavy elements is 10x higher than cosmic radiation could explain.
But is it 10x higher than could be explained if somewhere in its 13+ billion
years it went through a stellar nursery full of metal-rich elements?

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balsam
Actually I believe that the amount of heavy elements in that star was lower
than expected. They used the ratio of heavy elements (uranium and thorium) to
date the star, not the quantity. This star, I believe, is what is called a
Population II (low metallicity) star. Older stars have lower amounts of heavy
elements, and the yet-to-be-observed Population III stars are posited to have
no heavy elements whatsoever.

<http://en.wikipedia.org/wiki/Metallicity>

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EwanG
Not so important for it's age, but for what it tells us about when both first
and second generation stars likely formed. Which helps in determining how well
current models hold up.

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pdwetz
Yet another score thanks to Hubble. The progress in Astronomy and Cosmology
since the 90s is quite remarkable and fun to follow.

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dak1
Is there an explanation anywhere for how it's even possible for this type of
star to live this long?

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andrewcooke
i think you're misunderstanding slightly why this is important.

it's not surprising for small stars to live a long time (they burn quite
slowly). what's surprising is that we don't see any _older_ than about 14
billion years old.

so that suggests that the universe is only that old.

and really, to astronomers, that's not surprising either, since the universe
is known to be that old from other measurements.

what's actually surprising is that this star matches the universe's age so
closely when it contains some elements other than hydrogen or helium. since
that implies that it wasn't one of the first stars made (which would be pure
hydrogen and helium), but a star made from remnants of other stars. so it is
at least "second generation". so there must have been some stars of _short_
lifetime before it. and it's actually tricky to fit that in, given how we
think stars are created and how the universe evolved (the real problem is that
the hydrogen starts out fairly evenly spread out and needs time to clump,
under gravitation, to form the first stars - the density fluctuations that
describe this are constrained by observations of the microwave background,
which is quite smooth).

[some more background to make this consistent: the universe "started" as
hydrogen; large stars, which live a short time, can make other elements than
helium from hydrogen; small stars, which live a long time, make only helium
from hydrogen.]

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gus_massa
I think that your explanation is essentially correct. But most of the Helium
was formed during the 20 minutes after the Big Bang, not in the stars:
<http://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis>

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andrewcooke
oh, you're right. sorry, i will fix that. oh, no i won't - the edit window has
expired. how embarrassing.

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gus_massa
It's not embarrassing. I learned it only a few years ago and I was very
surprised. And looking for more information, today I learned that the Milky
Way is a _barred_ spiral galaxy.

When I was young the Big Bang only produced Hydrogen and the Milky Way had no
bars :) . <http://xkcd.com/1053/>

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andrewcooke
well, it's more embarrassing when you know i've made observations that
measured the amount of that helium... :o(

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iwwr
It's still a population II star, we have yet to find a genuine pop III (formed
entirely of hydrogen and helium). Surely there would have been some small pop
I stars from that early on. Or is it that stars may have been 'polluted' with
heavier elements after formation?

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ChuckMcM
I just don't get why its close to us. I mean I understand that if stars were
evenly distributed there would be one nearby, but they clump into galaxies,
and our galaxy isn't one of the 'first' ones so why is it here?

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btilly
_...our galaxy isn't one of the 'first' ones..._

That would be a misconception on your part. Excepting galaxies created due to
collisions between other galaxies, all galaxies are believed to have been
formed around the same time, and then got separated by the expansion of the
universe. So yes, we are one of the first galaxies..just like every other
galaxy. Thus we had stars created at all points of time, and some have
survived.

That said, there is a more interesting question underlying "why its close to
us" that deserves comment. It turns out that the Sun has a tendency to
oscillate up and down through the galactic halo. This is good for the Earth,
because it limits our time spent in neighborhoods where there is a lot of
other stuff we can run into. However early star formation took place in the
galactic plane, so most old stars are very near the galactic plane, and
therefore the Sun is usually not close to them.

I believe that the period of the oscillation is somewhere in the neighborhood
of 64 million years, so we punch through the plane about every 32 million
years or so. We last passed through an estimated 3 million years ago, and are
currently about a hundred light years away from the plane, so we are still
near objects in the plane, including old stars like this one. But in another
10 million years, we shouldn't be!

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balsam
Do you know if this punching of the galactic plane coincides with extinction
events?

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btilly
There has been contradictory research on that exact question.

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ck2
Only in astronomy can you "give or take 700 million years".

Geologists must be jealous, lol

So technically that star is long gone now, these are just distant pictures
from history.

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rietta
Actually, according to the article HD 140283 is _only_ 190 light years away.
That's practically right next door to us. So no, the star could quite possibly
still be alive and well in its old age.

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ck2
Ah you are right and given the theory that the universe is expanding, it may
have been even closer to us at one point.

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gus_massa
The expansion of the universe is visible in the very very very big scale. The
galaxies are generally spreading away from one another. But it is only the
general direction. The gravity makes them move in complex trajectories so some
of then are aproaching or even colide.

The Milky Way ~100,000 light-years in diameter, so this star is inside it.
Inside a galaxy the movements of the individual stars are even more complex,
so they get closer or more distant.

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Nick_C
Anyone know its apparent magnitude? I can't find anything in my usual sources
and google isn't helping.

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gus_massa
Apparent magnitude: 7.223

Extracted from / More information / Images : [http://server7.sky-
map.org/starview?object_type=1&object...](http://server7.sky-
map.org/starview?object_type=1&object_id=1408002&object_name=HIP+76976)

