The observable, universe reaches the "big bang"

The VLT has detected a new kind of faint galaxies not observed before.
Spiral galaxies 10 Billion light years from us:
http://www.eso.org/outreach/press-re.../pr-17-04.html
Quote:
The newly discovered galaxies are thus seen when the Universe was about
3,500 million years old, i.e. 10,000 million years ago. But from the spectra
taken, it appears that these galaxies contain stars with ages between 1,000
and 2,000 million years. This implies that the galaxies must have formed
accordingly earlier, and that they must have essentially completed their
assembly at a moment when the Universe was only 1,500 to 2,500 million years
old.

End quote

I am sorry, but in my stupid layman frame of mind I can't imagine a galaxy
without at least *one* star like our sun. And the sun is 5 billion years
old. I have to study that article to figure out how can you be certain that
the object so far away doesn't contain main sequence stars... I can
understand that we see the brightest stars of those galaxies only, but I
would not say that the other stars are absent just because their light
doesn't reach us.

The mass of those galaxies is big, but not bigger than big galaxies around
us. Supposing that they are like their similar cousins it would mean that
the universe must be *at least* 15-20 billion years old, much older than
current big bang theories allow.

This continuing flux of data indicating the presence of very old objects at
13 billion years (massive black holes see
http://chandra.harvard.edu/press/04_...ss_060104.html) that
confirms other reports of galaxies with a lot of iron and heavy metals, etc.
I have reported those findings often in this group.

Fact is that the observable universe starts reaching 13 billion years in its
continuos expansion by modern telescope technology. And there isn't any
evidence that anything changes. No traces of this bang, to the contrary: old
galaxies, black holes, and similar objects like in our immediate
neighbourhood.

In my layman frame of mind this means that the direct evidence of
observations imply that the universe must be at least 15-20 billion years
old. The bang (if any) must have been before that.

It is proposed that big galaxies grow by mergers of smaller ones. Galaxy
interactions are very slow. Our galaxy will crash into andromeda soon, they
are speeding to each other at full speed, but they will meet in 4 billion
years. The full interaction could last 1-2 billion years. For *one* merger!

To grow a big galaxy out of mergers still takes several billion years at
least, not counting the time to build the smaller ones. How many billion
years is our galaxy interacting with the LMC?

How many billion years took to digest the rests of the galaxies that merged
with the milky way? We still find traces of them, meaning the interaction is
not yet finished.

This population of galaxies has been discovered because of the VLT. I bet
that with the next scopes yet another kind of galaxies even farther away and
fainter as these ones will be discovered.

And the fact that those galaxies are big could be just that we can't
perceive the smaller ones. That's all!

ESO press release:
The VLT has detected a new kind of faint galaxies not observed before.
Spiral galaxies 10 Billion light years from us:
http://www.eso.org/outreach/press-re.../pr-17-04.html
Quote:
The newly discovered galaxies are thus seen when the Universe was about
3,500 million years old, i.e. 10,000 million years ago. But from the spectra
taken, it appears that these galaxies contain stars with ages between 1,000
and 2,000 million years. This implies that the galaxies must have formed
accordingly earlier, and that they must have essentially completed their
assembly at a moment when the Universe was only 1,500 to 2,500 million years
old.

End quote

That last bit is a little misleading, as is typical for press
releases. In context, "completed their assembly" means that the
galaxies have assembled themselves into a state where they are
recognizable as galaxies. It doesn't (or if worded better _wouldn't_)
imply that no further evolution will occur.

"jacob navia" wrote in message ...
I am sorry, but in my stupid layman frame of mind I can't imagine a galaxy
without at least *one* star like our sun. And the sun is 5 billion years
old.

What do you mean by "like our Sun?" If you mean one solar mass and
burning hydrogen, such stars are likely (but not certain) to be
present in high redshift galaxies. But if "like" means having
accumulated helium in the core from 5 Gyr of nuclear burning, then
there are no such stars in a galaxy less than 5 Gyr old.

I have to study that article to figure out how can you be certain that
the object so far away doesn't contain main sequence stars...

What makes you think there are no main sequence stars? A star doesn't
have to be old to be on the main sequence. After all, high mass stars
may only last a few million years altogether, but they still spend
most of their lifetimes on the main sequence. And stars form out of
molecular clouds and reach the main sequence in less than a few
million years.

I can
understand that we see the brightest stars of those galaxies only, but I
would not say that the other stars are absent just because their light
doesn't reach us.

Neither would anyone else. We have no direct evidence (as far as I
know) whether low mass stars are present or not. Technically one
would say we don't know whether the "stellar mass function" or the
"initial mass function" is the same as the local one or not. We would
expect some differences, because the metal abundance is likely to have
been lower in the past, and the IMF depends on the metal abundance
because it affects the cooling of molecular clouds in which the stars
form.

The mass of those galaxies is big, but not bigger than big galaxies around
us. Supposing that they are like their similar cousins it would mean that
the universe must be *at least* 15-20 billion years old, much older than
current big bang theories allow.

Again what do you mean by "like?" What reason do you have for
believing that a young galaxy contains old stars? And where do you
get the mass estimate? I would expect the early galaxies to be on the
whole less massive than local galaxies, but I don't think the data
exist to say for certain.

This continuing flux of data indicating the presence of very old objects at
13 billion years (massive black holes see
http://chandra.harvard.edu/press/04_...ss_060104.html) that
confirms other reports of galaxies with a lot of iron and heavy metals, etc.

Why do you believe these objects were old when they emitted the light
we see now? I don't see anything in the press release that would give
that impression.

There is indeed evidence that lots of metals were created very early
in the history of the Universe. That's a bit of a surprise, but only
a bit. You might want to look up the "G subdwarf problem," which has
been known for at least 30 years, probably longer. What seems to have
happened is that a bunch of very massive, very short-lived stars
formed very early in the history of the Universe. This population,
sometimes called "Population III," had virtually no members of low
enough mass to last very long. Thus Pop III stars created the early
dose of metals and then vanished. Further observations of distant
objects should reveal whether this scenario is right or wrong.

Fact is that the observable universe starts reaching 13 billion years in its
continuos expansion by modern telescope technology. And there isn't any
evidence that anything changes. No traces of this bang, to the contrary: old
galaxies, black holes, and similar objects like in our immediate
neighbourhood.

The distant population looks quite different from the local
population. The most obvious difference is the number of active
nuclei, but in general luminosities and star formation rates were
higher in the past. Working out the details is very much a topic of
ongoing research. In particular, it is one of the prime objectives of
the Spitzer mission.

It is proposed that big galaxies grow by mergers of smaller ones. Galaxy
interactions are very slow. Our galaxy will crash into andromeda soon, they
are speeding to each other at full speed, but they will meet in 4 billion
years. The full interaction could last 1-2 billion years. For *one* merger!

You are looking at one example and not considering that galaxies were
more numerous (though smaller) and closer together in the past than
they are now. Also, the Local Group is not a very dense region of
space.

To grow a big galaxy out of mergers still takes several billion years at
least, not counting the time to build the smaller ones.

Perhaps you would like to show your work? Or even an order of
magnitude calculation? Models in the literature come to quite a
different conclusion.

This population of galaxies has been discovered because of the VLT. I bet
that with the next scopes yet another kind of galaxies even farther away and
fainter as these ones will be discovered.

That's a good bet. See above about Population III. Although we might
worry that the Universe wasn't transparent when Pop III was around. I
look forward to finding out.