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John Kierein
2002-Apr-25, 07:32 PM
Nobody on the General astronomy board wants to comment on my post, so I thought I'd try here.
http://www.badastronomy.com/phpBB/viewtopic.php?topic=1145&forum=2&5

Silas
2002-Apr-25, 08:08 PM
The best astronomers in the world, and you call them "dumb?"

If they have found stars in our own galaxy that are 12 to 13 billion years old, that would set a lower limit, right? Meanwhile, doesn't the Hubble constant set the upper limit?

You may disagree with the Hubble constant -- and that's your right, of course -- but it doesn't make anyone "dumb" for their accepting it as the cosmological state of the art.

I intend to try to learn more about how these "clockwork stars" work.

Silas

Chip
2002-Apr-25, 08:20 PM
John Kierein wrote: "....
If you believe this link: http://www.flatoday.com/space/explore/stories/1999b/060299h.htm
the universe should be 15 to 20% younger than 12-13 billion years old. But that's only if you think the red shift is doppler. Of course the fact that there are stars older than that in our own galaxy makes this screwy unless the red shift is not doppler."


Whenever you have a situation where it boils down to cosmic questions being answered by either "A" or "B" -- with a "black or white" choice and no options, then it seems to me that something isn't quite right, and there may be a flaw in the reasoning.

This may sound terribly pedestrian of me, but I think it would be best to begin with the minority theory that runs counter to the mainstream, and assume that it is flawed somewhere. This is hard to do if the counter theory is dear to one's heart and seems so right by many standards, but it is necessary to assume fallibility and search for it. If after covering every angle, it still seems to work, then we should look into the mainstream concepts for loopholes. Even then, it may seem that there is actually a third alternative that has been overlooked.
/phpBB/images/smiles/icon_wink.gif


<font size=-1>[ This Message was edited by: Chip on 2002-04-25 16:21 ]</font>

2002-Apr-26, 09:27 AM
<a name="20020426.1"> page 20020426.1 aka yeah, YUCK
On 2002-04-25 16:20, Chip wrote: To: o
Ok i'll admit little interest in 12 Billion Yrs
or 20 {whatever the number if there was 1}
or whether the cosmos is comming or going
or allready a has been.. As Far as Red Shift?
Crompton, Doppler or some third party
I kind of like the Electron Skin verses
there once was an electron
with hair in his chin
he said to him self
after a grin
if i shave it off
i'll have a faster spin
and thereafter, Red Shift
began to begin 1:24 A.M. 2-4-26 HUb'

Spaceman Spiff
2002-Apr-26, 02:08 PM
Yes, that's right. We are THAT dumb. Why
would an astronomer EVER think taking
the ages of stars in distant galaxies into
account when estimating the "age" of the
universe? We have to be told these things,
ya know. /phpBB/images/smiles/icon_wink.gif

But seriously folks, Mr. Kierein, as usual
makes an totally unsubstantiated statement
and then declares astronomers to be as dumb
as posts for not realizing our "mistake".

Where is the evidence? That's the first
question that needs to be asked when claims
are made for this or that.

Whatever information we do have from
distant galaxies generally indicates YOUNG
populations of stars participating in
spectacular "starburst" activity. We cannot
measure the light of individual stars in
distant galaxies (other than from an
occasional supernova).
We don't even measure the light
of white dwarf stars in M31 for the simple
reason that they are too darned dim!

What we do measure
is a composite spectrum from millions or
billions of stars (depending upon the
situation). We then model that composite
light with various populations of stars (we
have computer models that tell us how the
spectrum of a starburst changes with time -
as the various types of stars come and go).

So until somebody measures an ancient star
in a high redshift galaxy, then the so-called
problem introduced by Mr. Kierein does not
exist.

John Kierein
2002-Apr-26, 02:50 PM
All the press including CNN is saying the data gives the age of the universe. Nobody corrects them. This is BAD ASTRONOMY. The data only says that these stars in our galaxy are that age and to say the universe is only 1 billion years older than the age of the stars in our galaxy is just WRONG!

What do you mean it's unsubstantiated? The NICMOS data clearly shows that distant galaxies contain old stars just like our galaxy and there is no reason to suggest that they don't contain stars of the same age as ours. Their deep sky image shows plenty of spiral galaxies just like ours. When compared to the visible data, both the older stars and younger stars show up, the young stars in the visible, and the OLD stars in the near IR. It simply doesn't follow any logic at all to say that by determining the age of some of the stars of our galaxy that they are determining the age of the universe! I can't believe you guys can defend this conclusion! It flies in the face of the data.

Note this statement from this web site:

http://www.cosmiclight.com/galleries/deepfield.htm

"Astronomers found this supernova in 1997 during a second look at the northern Hubble Deep Field [top panel], a tiny region of sky first explored by the Hubble telescope in 1995. The image shows the myriad of galaxies Hubble spied when it peered across more than 10 billion years of time and space. The white box marks the area where the supernova dwells.

The photo at bottom left is a close-up view of that region. The white arrow points to the exploding star's home galaxy, a faint elliptical. Its redness is due to the billions of old stars residing there. "

How can the universe be only the age of our galaxy in light of this? (No pun intended.)

<font size=-1>[ This Message was edited by: John Kierein on 2002-04-26 10:53 ]</font>

<font size=-1>[ This Message was edited by: John Kierein on 2002-04-26 11:09 ]</font>

Spaceman Spiff
2002-Apr-26, 04:08 PM
Agreed. The age of a star does not equal
the age of the universe. Even the articles
I read said that - and if CNN did not make
this distinction, then shame on them (though
are we supposed to rely on CNN for our
understanding of science? or do you think
that maybe the astronomers know better?).
It's just that these stars are apparently
very old, and so they set interesting bounds
on the age of the universe (stars can't
be older than the galaxy or universe they
inhabit) -- unless of course you **believe**
the universe has no age. But science isn't
about belief. It's about evidence.

re. the ages of stars in distant galaxies.
John, I have already had this discussion with
you. I will not get into a back and forth
with you, because it's useless. So for the
rest of the readers....

The NICMOS data, and all other data,
observe changes in galaxy morphology, type,
interaction frequency, etc. There are no
"gaping wounds" (yet) in the current paradigm
of an evolving ~14 billion year old universe.

The interested reader may want to see these:
http://lanl.arXiv.org/abs/astro-ph/0204315
and
http://xxx.lanl.gov/abs/astro-ph/9912146

but there are many more.

re. the Type 1a supernova discovered by HST.
The redshift of this galaxy has been measured
to be about 1.73. At this redshift, a 14.1
billion year old universe was already 3.8
billion years. A 3+ billion year old
elliptical galaxy will not likely be
dominated by the light of hot stars. On top
of that its spectrum is shifted to longer
wavelengths by a factor of almost 3 -- so
a multi-color filter image will tend to make
that object look redder than its stars
actually are. Isn't 3 billion years old
enough for you, John?

But also keep in mind....
Not all galaxies are expected to have formed
at the same time. Not all galaxies are
expected to have the same star formation or
merger histories (the latter tends to convert
whatever gas is present into stars - a la the
Antennae galaxy pair). The fields of galaxy
formation and evolution are new, yet rapidly
expanding (no pun intended). Our
knowledge and understanding are far from
anything resembling mature.

But the bottom line is that nobody has found
a 10 billion year old population of stars in
a high redshift galaxy, regardless of what
Mr. Kierein claims. It would be the
astronomical find of the century. Astronomers
are now spending a lot of their efforts in
the study of high redshift galaxies, and if
there are 10 billion year old populations of
stars to be found at redshifts above 2 and 3,
(even z = 1 would be interesting for 10 Gyr
old stars) then we'll eventually find them.

Until then, you'll have to stay tuned.


<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-04-26 12:11 ]</font>

<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-04-26 12:12 ]</font>

The Bad Astronomer
2002-Apr-26, 04:17 PM
I'll just note a common misconception here: red stars are not necessarily old. They are born red, so a star a few million years old (or less) can still be red.

An elliptical galaxy generally forms stars in an initial burst and then stops. After a while, perhaps a few million or tens of millions of years, the blue stars explode, leaving the redder ones. That's why ellipticals tend to be redder than spirals; spirals have ongoing star formation, so there are still blue stars being formed.

So when you look at an elliptical, it is red not because it is old in absolute terms, but because it is old enough that the blue stars are gone.

So even galaxies that are young when compared to the age of the Universe can still be red, if they don't have ongoing star formation.

John Kierein
2002-Apr-26, 04:53 PM
The article and CNN said that all the old stars in our galaxy were formed a billion years after the big bang started. It implied that there is not ongoing galaxy formation. I disagree with that and I agree with Spiff that not all galaxies were formed at the same time. In fact, I certainly think that individual stars were not all formed at the same time. The statement that the age of the stars in our galaxy plus a billion years is the same as the age of the universe is so idiotic to me that I can't help but call it a dumb statement. It makes me angry to hear people saying such an idiotic thing to promote the big bang. It just isn't science any more. It's a religion.

Theories seem to think that spirals were formed from galaxies colliding and we see that happening all over the place, continuing today when they should be flying away from each other. We see spirals as far out and from as long a time ago as we can see. I think the evidence is just about overwhelming that the universe is not the age of the oldest stars in our galaxy plus 1 billion years. I think we are seeing things that are much older than that. And I'm not even considering whether there was a big bang or not. They just made that 'age of the universe' thing up to be comfortable with a big bang theory.

Personally, I think that it's an "Endless, Boundless, Stable Universe". If it's endless then it's always been there.

By the way BA, are you trying to tell me that galaxies near the beginning of the big bang quit forming stars? But our galaxy has existed for 10 billion years longer than them and is still actively making stars? Sounds mighty anthropomorphic to me. You would probably say we're really special in a very special place in the unverse, much more special than those distant galaxies. Sounds like Ptolemy putting us in the special place at the center of the universe. Next you'll go back to epicycles.

<font size=-1>[ This Message was edited by: John Kierein on 2002-04-26 13:01 ]</font>

GrapesOfWrath
2002-Apr-26, 05:44 PM
On 2002-04-26 12:53, John Kierein wrote:
The statement that the age of the stars in our galaxy plus a billion years is the same as the age of the universe is so idiotic to me that I can't help but call it a dumb statement. It makes me angry to hear people saying such an idiotic thing to promote the big bang.

But that's a personal problem. Otherwise, you have to allow other people to get angry with you over these issues. Why be surprised when they do?

Silas
2002-Apr-26, 06:05 PM
On 2002-04-26 12:53, John Kierein wrote:
The article and CNN said that all the old stars in our galaxy were formed a billion years after the big bang started. It implied that there is not ongoing galaxy formation. I disagree with that and I agree with Spiff that not all galaxies were formed at the same time. In fact, I certainly think that individual stars were not all formed at the same time. The statement that the age of the stars in our galaxy plus a billion years is the same as the age of the universe is so idiotic to me that I can't help but call it a dumb statement.

I've been reading on this, and it doesn't seem dumb at all. It's a deduction, and it is based on two premises.

1) A certain kind of star could only be formed in the very early life of the cosmos.

2) This kind of star cools down at a very precise rate, which can be measured.

If these are both correct, then the measurement of the lifetime of that kind of star -- no matter where it was, in our galaxy or in another -- would indicate the age (approximately) of our cosmos.

If either of these are incorrect, well, that's science for you.

It isn't dumb. It isn't malicious. It isn't invalid. It's science: it's making use of what we think we know, to try to learn more.

Ease up on the pejoratives, and explain why you think one or both of the premises is incorrect.

Silas

DoctorDon
2002-Apr-26, 08:03 PM
ObDisclaimer: Galaxy formation is not my specialty, but I've read about this and I think I can address two issues here:



On 2002-04-26 12:53, John Kierein wrote:
Theories seem to think that spirals were formed from galaxies colliding and we see that happening all over the place, continuing today when they should be flying away from each other.


By "should be", I assume you mean due to the Hubble flow. But the universal expansion only happens if local gravitational forces don't cancel it out. Hence the space between the sun and the earth is not expanding, and we see blue shifts in some of our closest neighbor galaxies (and *only* in close by galaxies). So galaxies can absolutely collide, and since galaxies are in clusters, they can keep colliding for a long time, until the clusters evaporate, which isn't going to be for some time yet.



We see spirals as far out and from as long a time ago as we can see.


I thought one of the whole points of the HDF was that those most-distant galaxies were all irregulars.




I think we are seeing things that are much older than that.


like what?



By the way BA, are you trying to tell me that galaxies near the beginning of the big bang quit forming stars? But our galaxy has existed for 10 billion years longer than them and is still actively making stars?


The level of star-formation going on now is *nothing* compared with what it was back beyond z=1! We know it peaks around z=1;
whether it holds steady or declines beyond that is still up for grabs because it's hard to measure beyond that, but looking back from *here*, there's a dramatic increase as you look back in time. Far from being a contradiciton of the Copernican principle, it's actually a *confirmation* of it, because if there is a universal decline in star formation, you would expect to see less of it going on where you live, and more as you look out into the past. Which is what we see.

All of this is talking about averages over whole galaxies. Of course, if the Earth were in the middle of the Orion Nebula, we *would* be in a "preferred" position where there is a lot of star-formation going on. Of course, if the earth were in the Orion nebula, chances are we wouldn't be here to talk about it, so there's the Anthropic principle for you.

Anyway, the point is you could well have a galaxy go through an active starforming phase, and then basically run out of (useful) gas, until it collides with another galaxy, which causes all kinds of shock fronts, which compress the gas that's there, giving star formation a big push and causing the colliding galaxies to light up light christmas trees. Well, very big, very explosive christmas trees, anyway. I think that is what we really observe happening, but like I said, it's not my personal field of expertise.

Don


<font size=-1>[ This Message was edited by: DoctorDon on 2002-04-26 16:04 ]</font>

John Kierein
2002-Apr-26, 08:18 PM
Hey Silas, since when do white dwarf stars only get created a billion years after the big bang?
"While extremely large stars typically end their lives in a dramatic explosion, called a supernova, white dwarf stars are the end of the evolutionary road for smaller stars, ones which never had a high enough central pressure or temperature to trigger thermonuclear reactions."
They are old. But stars like Jupiter (which radiates more than it receives from the sun and is called a low grade sun itself) could just as well become a white dwarf. Jupiter was only formed about 5 billion years ago.

John Kierein
2002-Apr-26, 08:32 PM
Hey Dr. Don, How do you know it peaks around z = 1. Could it be that you are ignoring the older stars whose peak energies are red shifted out of the observed spectral range so that it only SEEMS there are an excess of younger more newly formed stars? Let's see what SIRTF says about this. I can hardly wait!

Silas
2002-Apr-26, 11:19 PM
On 2002-04-26 16:18, John Kierein wrote:
Hey Silas, since when do white dwarf stars only get created a billion years after the big bang?


I don't know... I think they were talking about a specific kind of white dwarf -- the ones they're calling "clockwork stars."

I don't know the details. All I'm trying to do is point out that you were hasty in referring to the reasoning as "dumb."

(The "Hollow Earth" theory -- now that's dumb!)

Silas

AKONI
2002-Apr-26, 11:57 PM
... But stars like Jupiter (which radiates more than it receives from the sun and is called a low grade sun itself.

Let me start out by saying A. This is my first post and B. I research history not astronomy so most of these topics are rather new to me, but astronomy has become the latest thing I want to learn about.


Okay,.. Jupiter is considered a star? Yep, off topic for this discussion, but it was mentioned in this thread. Can someone explain this to me (or point me in the right direction to get the information myself where the explanation won't be over the head of a novice?), and also... Why have I never heard of this before?

Thanks.



<font size=-1>[ This Message was edited by: AKONI on 2002-04-26 19:57 ]</font>

Chip
2002-Apr-27, 12:31 AM
On 2002-04-26 19:57, John Kierein wrote:
"...But stars like Jupiter (which radiates more than it receives from the sun and is called a low grade sun itself..."

AKONI asked:
"...Jupiter is considered a star? ...Can someone explain this to me (or point me in the right direction to get the information myself where the explanation won't be over the head of a novice?), and also... Why have I never heard of this before? Thanks.


Chip's two cents:
Jupiter is a planet, a "gas giant". It does radiate energy as John stated, but that doesn't make it a star. It is gigantic, (as a planet) but it isn't large enough to be even a small star. It lacks the thermal nuclear reactions in it's core (which is believed to be rocky) to be anything like a star in structure.

Here is probably more than you'd care to know about Jupiter (http://www.seds.org/nineplanets/nineplanets/jupiter.html), but there are some interesting facts. /phpBB/images/smiles/icon_wink.gif

John Kierein
2002-Apr-27, 12:32 PM
Under the definition of a star as being an object that self radiates energy; i.e., one whose radiation is not just reflected energy, then Jupiter qualifies. The definition of a white dwarf given here: http://www.space.com/scienceastronomy/astronomy/galaxy_age_991229.html
is the definition from above. So it follows that Jupiter, since it doesn't radiate from thermonuclear radiation is a candidate to eventually become a white dwarf. It may be that Jupiter still isn't quite big enough and maybe it has to be a brown dwarf before it'll become a white dwarf.
Good luck in finding white dwarf stars in large red shift galaxies. They're so intrinsically dim you have a tough time finding 'em in our galaxy. But the data shows there are lots of old stars in the distant galaxies and there's no reason to assume that the distribution of ages excludes white dwarf stars.

As for Dr. Don's quote: "I thought one of the whole points of the HDF was that those most-distant galaxies were all irregulars." that was the original conclusion from the first HDF in the visible. That conclusion was proven WRONG when the HDF was repeated in the near IR by the Near Infrared Camera and Multi-Object Spectrometer. This Hubble instrument was added to Hubble and had a cooled detector that could image in the Near IR. This camera showed that NOT all the most-distant galaxies were irregulars, but had the same general distubion of shapes as nearby galaxies. The reason was that the original visible image only showed the young stars; the old ones were red-shifted out of the spectral range that the visible imager could see. When the near IR images were taken the old stars showed up and the entire galaxy shape could be discerned. Many were spiral that were previously thought to be irregular. Look here:
http://oposite.stsci.edu/pubinfo/pr/1998/32/pr.html
This goes to show that collisions are not necessary to invigorate star formation since the stars in the spiral arms are old and young new stars from star formation seem to be clumped near the galactic center in an irregular shape. It's much more likely that star formation is an ongoing process near galactic centers, than need to be triggered by collision. Distant galaxies have lots of old stars. How presumptive of these guys to think that the age of stars in our galaxy are representative of the age of the universe. It just doesn't follow!


<font size=-1>[ This Message was edited by: John Kierein on 2002-04-27 08:38 ]</font>

Kaptain K
2002-Apr-27, 05:07 PM
John,
The passage in the Space.com article...

white dwarf stars are the end of the evolutionary road for smaller stars, ones which never had a high enough central pressure or temperature to trigger thermonuclear reactions. emphasis added
...is flat out wrong. Stars (by definition) are either undergoing thermonuclear fusion or have, in the past, undergone fusion.
Main sequence stars (like our Sun and most stars) are fusing hydrogen into helium. When the hydrogen in the core of a star the size of the Sun or smaller is depleted, they do not have enough mass to initiate fusion of heavier elements. After blowing off their outer layers in a furious stellar wind, the core that remains is a white dwarf that gradually cools and eventually becomes a black dwarf.
Giant and supergiant stars have passed the hydrogen burning stage and are burning heavier elements. When enough iron accumulates in the core (iron fusion is endothermic) the star suddenly collapses. The resulting explosion is called a supernova. The remnant is either a neutron star or a black hole, depending on the mass.
Brown dwarfs are stars that are not massive enough for hydrogen fusion, but are large enough for deuterium fusion. After the deuterium is exhausted, they too cool off to become black dwarfs.
Planets do not have the mass to initiate fusion (even of deuterium) and will never become stars. Jupiter is a net radiator because of 1) nuclear fission and 2) the release of gravitational energy from its contraction since its formation.

The Bad Astronomer
2002-Apr-27, 10:14 PM
On 2002-04-27 08:32, John Kierein wrote:
Under the definition of a star as being an object that self radiates energy; i.e., one whose radiation is not just reflected energy, then Jupiter qualifies.

Under hat definition, I am a star.

Astronomers have no hard-and-fast definition for a star, but most would say it's a body that at some point in its life had sustained nuclear fusion in its core. That would include brown dwarfs with a mass of about 0.77 solar masses (which can have deuterium fusing in their cores for a short time) up to the biggest supergiant. Jupiter would not qualify.

John Kierein
2002-Apr-27, 11:03 PM
Well, in my book, you ARE a star!

Spaceman Spiff
2002-Apr-29, 06:40 PM
As usual, John just repeats what he wants to
be true, and ignores whatever evidence is
out there. And so I repeat. The evidence
currently lies in a universe with an evolving
star-formation rate (and no, John, that's not
because we haven't looked into the IR -- we
have. AND all big starbursts involve hot,
massive stars that put out most of their
light in the UV -- redshift just shifts that
into the optical). The evidence currently
also lies with evolving galaxy populations.
In regards to the latter, the interested
reader may want to see these:

a review on our current knowledge of galaxy
evolution:
http://lanl.arXiv.org/abs/astro-ph/0204315

and

the HST/NICMOS paper on the Hubble Deep Field
that finds clearly for morphological
differences between high and low redshift
galaxies (contrary to what John says):
http://xxx.lanl.gov/abs/astro-ph/9912146

As I said above, this area of galaxy
formation and evolution is a highly volatile
one right now, because the first bits of
evidence/data have just started coming in.
Our picture is far from complete, but what
pieces are present DO fit in with the current
paradigm. And if the time comes that the
data don't support it, then the paradigm will
be junked for a better description of
nature.

DoctorDon
2002-Apr-29, 07:41 PM
On 2002-04-26 16:32, John Kierein wrote:
Hey Dr. Don, How do you know it peaks around z = 1?


Because of graphs I've seen at colloquia and conferences, like this one:

http://www.noao.edu/noao/noaonews/sep97/pics/hi2.gif

Note the peak at z=1. Although like I said, the last couple of talks I saw on the subject claimed that the two rightmost points might be underestimated.

But like I also said, this is not my field of expertise.

Don

John Kierein
2002-Apr-29, 07:43 PM
C'mon Spiff. They say that there may be 15 peculiar galaxies in the distant sample when they expected to see 4 if it were like the local sample. How can you be sure this is significant? The distant sample is very hard to analyze and may be distributed over a very large variation in distance. How do you know that the peculiar ones may not just be slightly more luminous intrinsically and therefore show up at a greater distance? This is hardly evidence for evolution. Aren't peculiar galaxies just younger and more luminous? Pretty weak argument if you ask me. I agree with you that galaxies are not all formed at the same time. There should be a distribution of ages. The younger ones have brighter stars and the older ones have stars that have faded out and reddened. You should see more younger ones in a distant field just because they are brighter.
Also, this is something that can be easily biased. How do you choose the sample of nearby galaxies? The sample of distant galaxies was not large. There is easily some room for opinion here as to what is or is not peculiar. Someone who is desperate to find evolution can fool himself easily into finding it here.

<font size=-1>[ This Message was edited by: John Kierein on 2002-04-29 16:00 ]</font>

<font size=-1>[ This Message was edited by: John Kierein on 2002-04-29 16:12 ]</font>

Spaceman Spiff
2002-Apr-29, 10:45 PM
John, as I have said several times now: the
field is YOUNG and the evidence is just now
starting to trickle in from a whole array
of different sorts of studies (the one by
van denBergh et al. is just ONE such study in
just ONE subfield that is attacking the
problem). And we do know more about the
starformation rates as a function of
redshift(back to z ~ 1-2) than we currently
know about galaxy morphology evolution. But
that may soon change. I'll add another one:
the 2DF galaxy survey shows the evolution of
large scale structure with redshift. The
deeper and larger SLOAN galaxy survey, when
it's done will put its 2 cents in, too. And
so will MAP, PLANCK, SIRTF, NGST, and on and
on and on. I can't help it if that's not fast
enough...

There is nothing mature, at all, about this
field, and I don't have THE answers -- nobody
does yet. And so all I am saying is that:

1) the data from a wide range of sources
are consistent with an evolving universe.

2) there are no data (yet) that contradict
the current paradigm of a universe in which
stars and galaxies (as a whole) came into
existence roughly 14 billion years ago.

These points ARE contrary to the statements
you have been making, for sure. Astronomers
can only go where the data take them. Only
time and evidence will tell whether the
current paradigm will stand or fall.

3) AND astronomers are not being stupid, as
you so plainly put it.

4) Like Dr. Don, this is NOT my field of
expertise (mine is quasars, another pet-peeve
of John's).

If you want to see what has been going on
in the past few years, visit the Los Alamos
preprint website (not everybody puts their
papers there, but many do).

For some fun in clicking on a galaxy in the
Hubble Deep Field, then getting its redshift
(photometric and spectroscopic if possible),
and seeing how the galaxy's morphology
changes with filter....

http://www.astro.sunysb.edu/fsoto/hdf/hdf_fs.html

another one:
http://nedwww.ipac.caltech.edu/level5/Deep_Fields/mirror/hdfn/index.html

and for the HDF-South
http://nedwww.ipac.caltech.edu/level5/Deep_Fields/mirror/hdfs/index.html

that's all I wish to say on this subject.
Good luck!



<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-04-29 18:56 ]</font>

ToSeek
2002-Apr-30, 01:17 PM
On 2002-04-29 18:45, Spaceman Spiff wrote:
For some fun in clicking on a galaxy in the
Hubble Deep Field, then getting its redshift
(photometric and spectroscopic if possible),
and seeing how the galaxy's morphology
changes with filter....

http://www.astro.sunysb.edu/fsoto/hdf/hdf_fs.html


What amazes me as much as anything is that there are 1067 galaxies bright enough to get spectrums on in this tiny bit of sky. Awesome!

John Kierein
2002-Apr-30, 02:21 PM
So why did they just select 111 galaxies to prove galactic evolution?

Spaceman Spiff
2002-Apr-30, 11:10 PM
Here is a very simple test. Find me a grand
design spiral galaxy JUST LIKE M81, along
with its many populations types of stars
(young, intermediate, old) at a redshift
of 6. How about 5? 4? 3? 2? (astronomers are
smart enough to count down from 6). Milky Way
or M31 are ok, too. At what redshift DO these
sorts of spirals first show up? That's a good
question, right now.

Show me a grand design spiral, complete with
all the do-dads of M81's stellar populations,
at high redshift, and then astronomers will
agree that there is a problem with the
current consensus paradigm.

Depending upon the severity of the "problem",
this could mean anything from re-evaluating
the parameters that govern the expanding
universe (we just had one of those with the
recent data from the Type Ia supernovae - if
that result holds up), to re-evaluating our
still nascent models for galaxy formation,
to abandoning the big bang paradigm, to
abandoning rationality (just kidding on that
last one).

Of course, astronomers will find them, IF
they are out there. You'll just have to
allow us some time....


<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-05-01 11:52 ]</font>

John Kierein
2002-May-01, 01:55 PM
"The NICMOS images reveal many of the objects to be ordered spirals and ellipticals similar to those in the local universe." This quote is taken directly from the link you gave me and I repeat it here.
http://xxx.lanl.gov/abs/astro-ph/9912146

One problem with imaging very distant objects is that we are reaching the limits of resolution for these. The new ACS will help a lot in this regard, but unfortunately it is not a great IR instrument like NICMOS, so the old stars will still be out of the spectral range. But the ACS does have some near IR capability. http://acs.pha.jhu.edu/instrument/overview/
The new experimental refrigerator for NICMOS will allow us to get some data at the NICMOS resolution, too.

<font size=-1>[ This Message was edited by: John Kierein on 2002-05-01 10:15 ]</font>

David Hall
2002-May-01, 02:31 PM
On 2002-04-29 18:45, Spaceman Spiff wrote:

For some fun in clicking on a galaxy in the
Hubble Deep Field, then getting its redshift
(photometric and spectroscopic if possible),
and seeing how the galaxy's morphology
changes with filter....

http://www.astro.sunysb.edu/fsoto/hdf/hdf_fs.html


Man, that's a pretty cool site. It must have been murder setting up the area map for the HTML coding.

Spaceman Spiff
2002-May-01, 03:50 PM
re. the John's quote from the paper I
supplied about the NICMOS imaging of
the HDF......

Yes, but Mike Corbin (a colleague of mine)
was not speaking of the highest redshift
galaxies in the HDF. Most of the galaxies
in that image have redshifts between
0.05 - 1, corresponding to lookback times
between 0.8 - 8 billion years ago (for
today's favorite flavor of cosmological
parameters). The Milky Way's disk appears to
have matured about 8 billion years ago.
The MW's disk began forming about 11 billion
years ago.........
11 billion years of lookback time corresponds
to a redshift of about 2 (again for today's
favorite flavor of parameters). Given the
admittedly scanty data (but we have more than
was reported by van den Bergh's group, and
much more is to be gathered), spiral galaxies
(with present epoch characteristics) appear
to be missing above redshifts of 2.

Whatever the case may be, we sure as heck
have never found an M81 look-alike at high
redshifts. And we have looked - not enough
or deep enough - but we have looked in the
infrared: with NICMOS and with the VLT and
other ground scopes working in the IR.

Something else to keep in mind is that the
HDFs and the new ACS galaxy images included
a near infrared filter (around 8140A,
so-called 'I band'). Note too that the SUNY
website for the HDFs pages I gave links to
(above) also included J,H,K images -- these
are well into the infrared (1.1-2.2 microns);
done from the ground (KPNO 4-m telescope).
So we are not totally in the dark about what
redshifted galaxies look like in the
infrared (high redshift galaxies should look
like nearby galaxies do at optical
wavelengths - if there is no evolution going
on).

I'll be the first to agree with John that the
investigation into the history of star and
galaxy formation in the observable universe
is just beginning. But I will disagree with
John that there are NOW data that strongly
contradict the current paradigm. There aren't
yet even any red flags.

ACS will help, but in the end, HST is limited
by the "puny" 2.4 meter mirror. We will have
to await the NGST. In the mean time the 8-10m
monsters on the ground are beginning to do
spectacular work -- they'll be chiming in
with interesting constraints while we wait
for the NGST. These are exciting times to
be an astronomer.


<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-05-01 11:51 ]</font>

<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-05-01 11:55 ]</font>

<font size=-1>[ This Message was edited by: Spaceman Spiff on 2002-05-01 11:57 ]</font>

ToSeek
2002-May-01, 03:52 PM
On 2002-05-01 10:31, David Hall wrote:
Man, that's a pretty cool site. It must have been murder setting up the area map for the HTML coding.


That's what grad students are for.