An old galaxy at z=7.1

On 3/6/2015 8:59 AM, jacob navia wrote:
Le 04/03/2015 20:55, wlandsman a écrit :
There are many possible clear and definitive tests but here's a simple
one -- find any object that has an origin more than 13.8 billion years
ago.
..
..
..
If we take your argument further, if you see an object that is X years
old with an universe thatis only Y years old (YX) that disproves BB
theory too.

The argument was not about disproving BB, the question was
what result would (the words of Robert O's message
lead us
to think that there is a problem with our theoretical
model of the early period of expansion?"

So there could be other errors than the BB concept (like
insufficiently taking into account discrete scale relativity,
or other shortcomings. That would remain to be seen then!)

...
The new MUSE instrument at ESO is also pretty incredible. It can see
objects in the HDF South that Hubble did not see at all, AND taking
their spectra!

I think it will be that instrument that will bring the big bang to explode.

Actually I don't see how _that_ would disprove it.. But I do
hope the instrument will teach us more about the 96% (by mass)
of physics that we don't yet understand!

--
Jos

On Friday, March 6, 2015 at 10:20:01 AM UTC-5, Phillip Helbig (undress to reply) wrote:
In other words, if someone finds evidence that the universe is, say,
14.5 Gyr old, then there is no problem. (Of course, any new value would
also have its own error bar.) If the error bars overlap, one would
expect the values to converge as measurements become better. On the
other hand, convincing evidence that the universe is, say, 20 Gy old
would require more than just adjusting the estimate.

-----------------------------------------------------------

What you describe is how the plastic model-building version of science works.

Theories of principle can make definitive predictions that are
non-adjustable. That form of science has a lot more integrity, in my
opinion.

[Mod. note: like it or not, the BB model is based on observation of
the universe we actually inhabit, and its parameters are not derived
from first principles. Please, let's take both that and the obvious
responses pointing out failed non-adjustable predictions of
'competitor' models as read, and try to find something that's both
original and interesting to say. -- mjh]

On Friday, March 6, 2015 at 2:59:54 AM UTC-5, jacob navia wrote:
Le 04/03/2015 20:55, wlandsman a écrit :

Take a pair of binoculars, and look into the constellation of Libra.
There, you can see HD 140283, that lies 190.1 light-years away. Its age
was before estimated to 16 billion years. Now, NASA has brought that
down into 14.5 billion. Further tweaking by the astronomers will surely
bring that star into the desired range :-)


French astronomers have already brought the age down. Crevey et al.
(2015, http://adsabs.harvard.edu/abs/2015A%26A...575A..26C ) now
estimate the age as 13.7 +/- 0.7 Gyr if there is no reddening, and
12.2 +/- 0.6 Gyr for a very modest (but plausible) reddening (A_V =
0.1).

(This work is done by stellar astronomers, not by cosmologists.)

We are seeing now a dusty galaxy that must have formed in only 150
million years can you imagine?

It is hard for me to image a 150 million year old galaxy that is *not*
dusty. Try googling the phrase "dusty starburst".

Le 06/03/2015 17:14, Jos Bergervoet a écrit :
There are many possible clear and definitive tests but here's a simple
one -- find any object that has an origin more than 13.8 billion years
ago.
..
..
..


I note that you snipped the object older than the universe that can be
seen with a pair of binoculars...

The latest estimate (14.5 billion years +/- 0.8 Gy) is still older than
the universe as the big bang would have it.

In the *best* case this star is 13.7 billion years, so it must have
formed IMMEDIATELY after the supposed bang!!!

And this is an otherwise run of the mill star, that is in our nearest
neighborhood; just 190.1 light years away. What a coincidence isn't it?

[Mod. note: 1-sigma error bars are not a definitive range. If this
measurement were right (and it's already been updated, see wlandsman's
post) then we could say with ~99.9% confidence that the age is 12.1
Gyr, hardly a serious problem for the BB model. Posters are encouraged
to apply *basic* statistics to any numbers they want to introduce to
the discussion -- mjh]

Le 06/03/2015 16:20, Phillip Helbig (undress to reply) a écrit :
NASA has not "brought that down". Rather, estimates are improved with
time. That's why people continue to study objects which have been
studied before.

OK, but this is STILL older than the universe! 14.5 is bigger than 13.7
as far as I understood maths.

I am always accused of not bringing more "numbers", more "facts"!

OK. Here iks a number

FOURTEEN POINT FIVE that is bigger than 13.7.

OK, the error bars. Plus/minus 0.8 billion years, so in the BEST case,
this star was formed instataneusly after the bang since

14.5 - 0.8 -- 13.7 Gy

In the *best* case since in all other cases this star is older as the
universe...

But this fact will be "explained" away and we will go on as before.

In article ,
jacob navia writes:
http://www.eso.org/public/archives/r...8/eso1508a.pdf

This is an interesting paper, but because it's in _Nature_, not all
the information is given. In particular, it looks to me as though
the uncertainties on the physical quantities are underestimated, and
I don't see how the authors derive the expected equivalent width for
the C III] line. (It isn't in the reference cited.) A dust
temperature as low as 35 K also strikes me as unlikely; the CMBR
temperature is 23 K, after all. None of this changes the basic and
valuable result that there must be _some_ dust in the galaxy, and in
fact more of the galaxy's luminosity comes out in the rest-frame FIR
than in the UV.

There is a vast literature on processes that create and destroy
dust. Despite that, there are still large uncertainties about the
dust life cycle because the creation and destruction rates depend
critically on local environmental conditions and on the exact dust
composition. Also, dust _masses_ are notoriously hard to measure.
The age estimate for the stellar population of A1689-zD1 is 80 Myr,
and I see no reason why dust amounting to about 2% of the stellar
mass (by the authors' estimate; rather less by my estimate) cannot
have been created in that time.

As to A1689-zD1 contradicting the Big Bang, our present knowledge of
early galaxy formation and the progress of reionization is highly
uncertain. Better understanding of the early Universe is indeed a
prime objective of JWST. That said, a _rough_ picture of the timing
as presently understood is that the first galaxies might have formed
between redshift 11 and 20, substantial reionization (say 1% of the
volume ionized) begins around redshift 8 or lower, and reionization
is nearly finished (99% of the volume ionized) no later than redshift
5.5. Further data will refine or perhaps change these numbers, but
so far as I know, there are no existing data inconsistent with
them. As others have written, the new data on this galaxy are
consistent with these epochs.

Finally, what would it take to throw out the present Big Bang
picture? I can think of two obvious things: 1) an object at any
redshift older than the calculated age of the Universe at that
redshift, or 2) a microwave background temperature at any redshift
differing from (1+z)*2.7 K. (wlandsman mentioned #1.) Less obvious
but still sufficient would be failure to find any single set of
cosmological parameters consistent with all data. Of course such
contradicting observations would have to be confirmed and have low
uncertainties and systematic errors, not be simply 1- or 2-sigma
deviations or observations where the meaning is unclear. A couple of
decades ago, globular cluster ages were thought to constitute such a
problem, but _Hipparcos_ data showed the cluster distances were wrong
and therefore the ages were overestimated. As I wrote, at the moment
there's no problem despite considerable data.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

On Sat, 07 Mar 15, Steve Willner wrote:
Finally, what would it take to throw out the present Big Bang
picture? ... 2) a microwave background temperature at any redshift
differing from (1+z)*2.7 K.

I wonder what you'd think of this paper: "The Temperature Of The z=8.4
Intergalactic Medium" -- http://arxiv.org/abs/1503.00045 .
They measure the "spin temperature" of the IGM at z=8.4 and are
hard-pressed to reach as high as 10K. I don't understand much of the
paper, though.

Eric

On Saturday, March 7, 2015 at 3:45:50 AM UTC-5, jacob navia wrote:


I note that you snipped the object older than the universe that can be
seen with a pair of binoculars...

Sigh. The name of this star is HD 140283 -- it is the nearest halo star to the Sun with V = 7.2 and a distance of 190 light years in the constellation of Lyrae. The French astronomers I quoted obtained interferometry for this star and greatly reduced the uncertainties in its age determination. Their best age determination is 13.7 +/- 0.7 Gyr if there is no reddening, and 12.2 +/- 0.6 Gyr for a very modest (but plausible) reddening (A_V = 0.1).

The latest estimate (14.5 billion years +/- 0.8 Gy) is still older than
the universe as the big bang would have it.

No. The latest estimate is from the French paper. Please don't quote
an obsolete press release but use the improved results (
http://adsabs.harvard.edu/abs/2015A%26A...575A..26C ). And as the
moderator noted, please don't ignore the 1 sigma error bars.

I find it remarkable that cosmoslogists are able to estimate the age
of the universe but studying tiny temperature fluctuations in the
microwave background. And this age turns out to be entirely consistent
with the ages of the oldest stars and of high redshift galaxies.

--Wayne

In article , wlandsman
writes:

I find it remarkable that cosmoslogists are able to estimate the age
of the universe but studying tiny temperature fluctuations in the
microwave background. And this age turns out to be entirely consistent
with the ages of the oldest stars and of high redshift galaxies.

Indeed. The CMB gives us lambda, Omega, and H, and hence the age. The
values for lambda, Omega, and H are also essentially the same as those
derived from other methods---several of them---without using the CMB at
all. It is thus not just the one parameter---age---which agrees from
several independent determinations, but the individual parameters used
to calculate it as well.

Le 08/03/2015 09:38, wlandsman a écrit :
Their best age determination is 13.7 ± 0.7 Gyr if there is no reddening,

and 12.2 ± 0.6 Gyr for a very modest (but plausible) reddening (A_V = 0.1).

quote
The adoption
of one particular result for AV then becomes arbitrary. In
this work we determine AV in the direction of the star along with
F(bol) using a SED fitting method, described below. However, we
also fix AV = 0.0 mag and discuss our results considering both
possible scenarios
end quote

It is interesting that you do not take into account the precise wording
of the authors of that paper. The reddening hasn't been observed by some
observers, the star is very near (just 190 ly) so this reddening
parameter looks highly suspicious to me, not "plausible" as you say.

This is very dangerous for an unbiased analysis of the data that in
astronomy can be very difficult to evaluate.

The authors of that paper conclude the abstract with:

quote
Theoretical advances allowing us to impose the mixing-length parameter
would greatly improve the redundancy between M, Yi, and
age, while from an observational point of view, accurate determinations
of extinction along with asteroseismic observations would
provide critical information allowing us to overcome the current
limitations in our results
end quote

They say that their accuracy can (and should) be improved!

You wrote:
quote
Please don't quote an obsolete press release but use the improved results
end quote

The paper you cite is from December 2014. I just wasn't aware of that
very new publication.

As I said, I see that we have reached the point where the age of the
star fits into the framework that many astronomers wish. But this is not
a final analysis, as the authors themselves write in their abstract.


To be continued!

jacob