Oldest star HD 140283

Le lundi 21 janvier 2013 07:52:53 UTC+1, Yousuf Khan a écrit*:
On 20/01/2013 11:54 AM, Mike Dworetsky wrote:

wrote:

The star HD 140283 lies 190 light-years away from the Sun.

It is 13.9 +/- .7 billion years old, whereas the Big Bang happenend

13.77 +/- s billion years ago.



Where do you get your numbers for the star's age? This looks like a

misquote.



I think this might be where he got it from:



"The team then exploited the fact that HD 140283 is in a phase of its

life cycle in which it is exhausting the hydrogen at its core. In this

phase, the star's slowly dimming luminosity is a highly sensitive

indicator of its age, says Bond. His team calculates that the star is

13.9 billion years old, give or take 700 million years. Taking into

account that experimental error, the age does not conflict with the age

of the Universe, 13.77 billion years."

Yes, thank you.


Nearby star is almost as old as the Universe : Nature News & Comment

http://www.nature.com/news/nearby-st...verse-1..12196



Statistically, what is the probability that HD 140283 is older than

the BB?



The error boundaries may overlap the age of the BB but no one thinks the

star is possibly older than the BB.

According to some hypothesis, the BB happened 13.77 +/- 0.059 Gyr ago.
In order to appreciate the signification of such value, one could look at http://en.wikipedia.org/wiki/Age_of_the_universe.
For instance, the age of the universe based on the best fit to WMAP data alone is 13.74 ± 0.11 Gyr.
Using this last value, one could infer that HD 140283, aged 13.76 ± 0.11 Gyr, is a little older than the BB.
Moreover, the first stellar generation must be older than HD 140283 itself.





Yes.



Yousuf Khan

On 21/01/2013 8:56 AM, wrote:
Not so long ago, many people thougt that our Earth was alone in the Universe.
Now, it is presumed that billions of Earth-like planets are present in our galaxy.
Why wouldn't very many HD140283-like stars exist in our galaxy?
And why wouldn't some of them be still older than HD140283?

There are likely to be other stars as old as, and possibly older than
this one. But what you'll find is that the age differentials are
starting to narrow. If they can determine its age to a narrower degree,
you'll find that they are approaching the same age.

These old stars are thought to be 2nd generation stars, Pop II stars.
The first generation stars are actually called Pop III stars rather than
Pop I (which are the currrent generation stars). So the generation
numbers and population numbers are reversed. Anyways, the first gen
stars, the Pop III, are the very first stars after the Big Bang, and
it's thought that we won't see any of these left over, as it's thought
that they were all supergiants which went supernova a long time ago, no
long-lived dwarfs among them. If they do see a pop III that's still
alive after all of this time, then it would be interesting for two
reasons: (1) that they actually found a Pop III star, and (2) that Pop
III stars could be so small.

For a Pop III star to stay alive from nearly the beginning of the Big
Bang to now, it would need less than 0.9 solar masses.

Yousuf Khan

On 21/01/2013 9:00 AM, wrote:
According to some hypothesis, the BB happened 13.77 +/- 0.059 Gyr ago.
In order to appreciate the signification of such value, one could look at http://en.wikipedia.org/wiki/Age_of_the_universe.
For instance, the age of the universe based on the best fit to WMAP data alone is 13.74 ± 0.11 Gyr.
Using this last value, one could infer that HD 140283, aged 13.76 ± 0.11 Gyr, is a little older than the BB.
Moreover, the first stellar generation must be older than HD 140283 itself.

Where do you get HD 140283, aged 13.76 ± 0.11 Gyr? The article is saying
13.9 ± 0.7 Gyr. Anyways, even if it is 13.76 ± 0.11, just so long as the
error bars fall within the BB, it's fine. If the error bars fall
completely (i.e. both the top & bottom) outside the error bars for the
Big Bang, then there might be something to talk about.

Back about 20 years ago, they were estimating that some stars were maybe
20 billion years old, but the BB was already known to be only around
13.7 billion years by then. In all cases, it was simply that we didn't
know stellar aging details well enough back then to make smaller error
bars for them.

Yousuf Khan

Le lundi 21 janvier 2013 16:13:30 UTC+1, Yousuf Khan a écrit*:
On 21/01/2013 9:00 AM, wrote:

According to some hypothesis, the BB happened 13.77 +/- 0.059 Gyr ago.

In order to appreciate the signification of such value, one could look at http://en.wikipedia.org/wiki/Age_of_the_universe.

For instance, the age of the universe based on the best fit to WMAP data alone is 13.74 ± 0.11 Gyr.

Using this last value, one could infer that HD 140283, aged 13.76 ± 0..11 Gyr, is a little older than the BB.

Moreover, the first stellar generation must be older than HD 140283 itself.



Where do you get HD 140283, aged 13.76 ± 0.11 Gyr? The article is saying

13.9 ± 0.7 Gyr.

Sorry, my mistake!

Anyways, even if it is 13.76 ± 0.11, just so long as the

error bars fall within the BB, it's fine. If the error bars fall

completely (i.e. both the top & bottom) outside the error bars for the

Big Bang, then there might be something to talk about.

I have to agree with you!




Back about 20 years ago, they were estimating that some stars were maybe

20 billion years old, but the BB was already known to be only around

13.7 billion years by then. In all cases, it was simply that we didn't

know stellar aging details well enough back then to make smaller error

bars for them.



Yousuf Khan

Le lundi 21 janvier 2013 15:59:06 UTC+1, Yousuf Khan a écrit*:
On 21/01/2013 8:56 AM, wrote:

Not so long ago, many people thougt that our Earth was alone in the Universe.

Now, it is presumed that billions of Earth-like planets are present in our galaxy.

Why wouldn't very many HD140283-like stars exist in our galaxy?

And why wouldn't some of them be still older than HD140283?



There are likely to be other stars as old as, and possibly older than

this one. But what you'll find is that the age differentials are

starting to narrow. If they can determine its age to a narrower degree,

you'll find that they are approaching the same age.



These old stars are thought to be 2nd generation stars, Pop II stars.

The first generation stars are actually called Pop III stars rather than

Pop I (which are the currrent generation stars). So the generation

numbers and population numbers are reversed. Anyways, the first gen

stars, the Pop III, are the very first stars after the Big Bang, and

it's thought that we won't see any of these left over, as it's thought

that they were all supergiants which went supernova a long time ago, no

long-lived dwarfs among them. If they do see a pop III that's still

alive after all of this time, then it would be interesting for two

reasons: (1) that they actually found a Pop III star, and (2) that Pop

III stars could be so small.



For a Pop III star to stay alive from nearly the beginning of the Big

Bang to now, it would need less than 0.9 solar masses.



Yousuf Khan

I do agree with your comments. Thank you again.

wrote:
Le lundi 21 janvier 2013 09:26:40 UTC+1, Mike Dworetsky a écrit :
wrote:

Le dimanche 20 janvier 2013 17:54:26 UTC+1, Mike Dworetsky a écrit :

wrote:



The star HD 140283 lies 190 light-years away from the Sun.



It is 13.9 +/- .7 billion years old, whereas the Big Bang
happenend



13.77 +/- s billion years ago.







Where do you get your numbers for the star's age? This looks like
a



misquote.







According to the 2013 AAS abstract by Howard Bond et al







http://adsabs.harvard.edu/abs/2013AAS...22144308B







the age and its formal error due only to parallax uncertainty is

13.30 ±



0.30 Gyr. They say there are larger uncertainties from stellar

parameters



and chemical composition that are larger than 0.30 Gyr, though the

abstract



does not quote what these add up to, though they say "considerably

larger".











Statistically, what is the probability that HD 140283 is older
than



the BB?







The error boundaries may overlap the age of the BB but no one
thinks

the



star is possibly older than the BB.



Mike Dworetsky



Thank you.



I read in the abstract that



"Within the errors, the age of HD 140283 is slightly less than the

age of the Universe, 13.76 ± 0.11 Gyr, based on the microwave

background and Hubble constant."



The BB happened 13.77 +/- 0.059 Gyr ago.



Not sure why your figure differs from Bond et al.





But our Galaxy must be older than HD 140283, thus older than the BB!



Oh no, that isn't necessarily true at all! Our galaxy was (and is
still

being) formed from many mergers of smaller galaxies over a long
period of

time. In the Hubble Deep Fields all you see for very early epochs
are small

irregular objects, few if any spiral galaxies at the earlier stages.

HD140283 could have come from the very early stages of star
formation in one

such fragment, and that could have merged into the forming Galaxy at
any

time.

Not so long ago, many people thougt that our Earth was alone in the
Universe.

Not everyone, though. But all were agreed that detecting Earth-like planets
would be very difficult, and only with the latest technology and space
probes like Kepler has it become possible to look for them and find them.

Now, it is presumed that billions of Earth-like planets are present
in our galaxy.

It's estimated/extrapolated from what we have already discovered, rather
than presumed.

Why wouldn't very many HD140283-like stars exist in our galaxy?
And why wouldn't some of them be still older than HD140283?


Of course there ought to be quite a few really old stars like this, but
detecting them and measuring them accurately enough to determine absolute
luminosity and hence age is very difficult, because most are far away and
typically in the galactic halo.

And yes, some could be even older, the quest continues. However, I can make
a reasonably confident prediction that we will not find any stars that are
verifiably older than the Big Bang. Finding stars formed a few hundred
million years later than that is a useful confirmation of the Big Bang
model.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

In article ,
Yousuf Khan writes:
http://www.nature.com/news/nearby-st...iverse-1.12196

This seems to be full of errors. The actual AAS abstract is at
http://adsabs.harvard.edu/abs/2013AAS...22144308B

The age it gives is 13.3+/-0.3 Gyr, but the error bar is only from
statistical uncertainty in the distance. The text says systematic
errors are much larger than this.

I haven't searched, but sometimes people put complete copies of their
posters online.

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