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Fraser
2007-Jul-11, 06:17 PM
Astronomers announced today that they've located the most distant galaxies ever seen, 13.2 billion light-years away, formed when the Universe was only 500 million years old. ...

Read the full blog entry (http://www.universetoday.com/2007/07/11/most-distant-galaxies-ever-seen/)

antoniseb
2007-Jul-11, 08:27 PM
It seems plausible that these are galaxies that distant, or perhaps discreet star-forming regions of galaxies that distant (given how small they seem to be). I look forward to any information that the JWST can give about them. The article itself allows some doubt.

thothicabob
2007-Jul-13, 02:46 AM
Hmm. I didn't read the article - I just read the heading here, but it seems to me that 500 myrs is a bit 'soon' for galaxies, no? I can see groups of stars forming in the regions where hydrogen's collected graviationally, and perhaps that's that they're referring to as galaxies? i would think it would take a bit more time for enough stars to form and enough 'structure' to develop for such groupings to really qualify as galaxies?

Still, being able to 'see' that far back is something. Two things are striking about this period in time, I think - it wasn't until after the first stars formed and went supernova that any sort of real chemistry was possible - before and during the first generation of stars, the universe was even more than 'deader than a doornail' - doornails couldn't even exist (no iron), let alone anything remotely that could be seen as potentially complex enough to imagine leading to something called "life".

Another thing that's interesting - as far 'back' (and 'out') as we can see, we're only really seeing to our visible horizon - if the universe really is about 160 bly's across, there's SO MUCH of the universe forever hidden from us...our visible sphere is only a small fraction. And this brings up a bit of a question: are the galaxies we now "see" as 12-13 blys away NOW actually about 70-80 bly's away (and all we're seeing is the light emitted from when they were "closer")? In other words, is all that we see really all there "is" (or was), and even if the sphere is now 160 blys across, what we 'see' is what is in it?

Or are there really regions (and galaxies within those regions) beyond our horizon that we've never seen (and never will)?

As I understand it, the likely reality is the latter (and if so, well, that's just something to think about, ain't it?), but I'd like to be sure I've got a good understanding. And if that's the case, has all that extra mass and energy been considered properly in determining if there's enough mass to cause a Big Crunch (assuming that the implication that expansion is re-accelerating could be an artificact of our misinterpretation of current observation/knowledge (not that I am saying it is, just hypothesizing here))?

lyndonashmore
2007-Jul-15, 10:16 AM
Mmmmmmh, a galaxy when the universe was only 500 million years old. Interesting.
Our galaxy, the milky way rotates (least where we are) once every 250 million years (http://answers.yahoo.com/question/index?qid=20070419005733AADMQBh&show=7)
That means that if this galaxy were us, the big bang would have gone off , everything whizzed out, clumps form and eh up! a galaxy is made - and yet in all this time it has only had time to rotate twice!
That is, from the BB itself to the 'formed' galaxy it could have only rotated twice.
I wonder how long it will be before they find a galaxy older than the universe. Anyone taking bets?
Cheers,
lyndon

antoniseb
2007-Jul-15, 10:51 AM
I wonder how long it will be before they find a galaxy older than the universe. Anyone taking bets?
I'm not a gambling man, but it is a safe bet that we will never find a galaxy older than the universe.

BTW, the 'galaxies' they are finding are only a few hundred light years across, and so they would rotate faster, not that rotating has much to do with the initial formation of the spherical inner core of the galaxy...

ArgoNavis
2007-Jul-15, 11:40 AM
Mmmmmmh, a galaxy when the universe was only 500 million years old. Interesting.
Our galaxy, the milky way rotates (least where we are) once every 250 million years (http://answers.yahoo.com/question/index?qid=20070419005733AADMQBh&show=7)
That means that if this galaxy were us, the big bang would have gone off , everything whizzed out, clumps form and eh up! a galaxy is made - and yet in all this time it has only had time to rotate twice!
That is, from the BB itself to the 'formed' galaxy it could have only rotated twice.


I am not sure why it needs to have rotated any set number of times - the images I see of galaxies in the early universe are just blobs. This is understandable given their distance, however it would appear to me that they are still in the process of formation.


Galaxy structure as we know it doesn't appear until much later.

Michael Noonan
2007-Jul-15, 12:28 PM
I'm not a gambling man, but it is a safe bet that we will never find a galaxy older than the universe.

BTW, the 'galaxies' they are finding are only a few hundred light years across, and so they would rotate faster, not that rotating has much to do with the initial formation of the spherical inner core of the galaxy...

Good to see you back again antoniseb.

I added a diagram so go with the thought 5844

In the start there was a large expansion so the light would have traveled in time, shouldn't there be significant cooling like red shift?

Is it possible this early light started as gamma ray bursts and the photons are less energetic due to red shift.

I am guessing the path of the light was curved through space as it expanded to reach us not straight. The bottom two pictures.

I am not good with the math so hopefully the diagrams aren't too awful.

antoniseb
2007-Jul-15, 12:42 PM
Is it possible this early light started as gamma ray bursts and the photons are less energetic due to red shift.

No. The light we are seeing from these distant galaxies (if this observation proves correct) comes from a time z=9. Thus the photons are stretched by a factor of 10. Gamma rays from this period would still look like gamma (or maybe xrays for low-end gammas), but these were infrared photons that had been red-shifted down from hard UV.

Even the Microwave Background is only redshifted by a factor of 1100. A one MeV gamma would only be redshifted into the xray region from that period.

Nice diagram though.

speedfreek
2007-Jul-15, 12:55 PM
Another thing that's interesting - as far 'back' (and 'out') as we can see, we're only really seeing to our visible horizon - if the universe really is about 160 bly's across, there's SO MUCH of the universe forever hidden from us...our visible sphere is only a small fraction. And this brings up a bit of a question: are the galaxies we now "see" as 12-13 blys away NOW actually about 70-80 bly's away (and all we're seeing is the light emitted from when they were "closer")? In other words, is all that we see really all there "is" (or was), and even if the sphere is now 160 blys across, what we 'see' is what is in it?

Or are there really regions (and galaxies within those regions) beyond our horizon that we've never seen (and never will)?

Currently, the estimated comoving distance (the distance that an object is now) to the edge of our observable universe is around 46 billion light years, so those most distant galaxies would be something closer than that. Let's look into this a little closer.

When we observe distant galaxies we see that their light has been "stretched" by the expansion of space whilst that light was making its journey. This "stretching" is known as redshift, where the absorption lines in an objects spectrum are shifted towards the red end of the spectrum (if they were shifted towards the blue end it would mean the object was moving towards us). We use the value z to show an objects redshift measurement.

The most distant galaxies we see have redshift values around z = 9 or thereabouts. I know that is an arbitrary figure on it's own, so I will add that a redshift of z = 1.5 is considered to mean an object is apparently receding at the speed of light. So the most distant galaxies are receding from us at apparent speeds that are faster than light. The reason we can see them is because they were a lot closer to us 13 billion years ago when they emitted the light we see today - it is estimated they were as little as 2 billion light years away at that time. Space was expanding as the light made its journey, and by the time it reached us, around 13 billion years have passed. They are now apparently receding faster than light, but were not when they emitted the light.

The thing about the expansion of space is that it is incredibly slow locally and it is a cumulative effect which means the further you look, the faster an object is receding. So the light was always able to make its way towards us through space that was expanding very slowly, but the cumulative effect is that the distance was 2 billion light years when it departed, and it took 13 billion years to arrive. Meanwhile, the expansion of space has put those distant galaxies well over 13 billion light years away!

But I mentioned a figure of 46 billion light years to the edge of the observable universe, didn't I? This is because space had already been expanding before those galaxies formed, and the expansion was faster earlier on. Right after the big-bang it is thought that all points were expanding away from each other at the speed of light, but immediately slowed from that, and was decelerating towards the present day, although we have some evidence that the expansion has "recently" started to accelerate again.

You may have heard of the Cosmic Microwave Background radiation, the "earliest" radiation we have measured, which was emitted something over 300,000 years after the big-bang. Well the CMB has a redshift of around z =1100! If the rate of expansion equates to z = 1100 over 300,000 years after the expansion started, and the expansion had decelerated to that point, imagine how far the "edge" of the universe might be by now. The estimate is around 46 billion light years, giving us an observable universe with a comoving diameter of 92 billion light years. Remember, by the time the galaxies formed after 500 million years, the expansion equates to a redshift of something around z = 9. That's a massive deceleration of the expansion before those galaxies formed! In the time between the CMB and the first galaxies, the expansion was huge!

But what if there were galaxies outside our observable universe? Well if the most distant galaxies we can see were only 2 billion light years away when they formed, how can we see a galaxy that was 4 billion light years away at that time? It's light has not reached us yet, and due to the cumulative effect of the expansion of space, it might have already been receding apparently faster than light at that time, but we will still see it one day. We will continue to see objects that are more distant than the most distant objects we see right now until such a time that the expansion of space is so fast that light cannot approach our "hubble distance" from the other side and creep over it, but that epoch is currently a long way off. So actually, our observable universe includes all the galaxies that are within 46 billion light years of us right now. But it might be a very long time before we can actually observe some of them!

This link (http://www.atlasoftheuniverse.com/redshift.html) is a good guide to get you started on understanding how the expansion of space relates to all this.

Michael Noonan
2007-Jul-15, 05:54 PM
This link (http://www.atlasoftheuniverse.com/redshift.html) is a good guide to get you started on understanding how the expansion of space relates to all this.

Thanks speedfreek

This has been the thing that confused me most. I had been of the idea that an expansion for the first 130,000 years could only produce a sphere 260,000 in diameter and an expansion for 300,000 years a diameter of 600,000 light years.

Having the space swell between this expansion gets rid of the problem of two starting beams of light not exceeding the speed of light away from each other. It just seemed too short a timeframe for the inflationary epoch to have achieved such a diameter and high z factor.

Also in this soup of energy no particular direction would have been important as the interaction of the expanding energy should have kept the whole of the inflation solid with energy. This would point to the inner inflation retaining more heat than the edges forming the boundary of the universe.

That was why I saw no problem with all the energy delivered instantly or over the entire inflation. So to a high energy particle its time to inflate would have been near zero for the whole of the inflation. As larger lower energy particles formed they couldn't travel at anywhere near light speeds due to relativity.

If this soup of the early inflation did cool at the edges first, then would the whole of the inflated area therefore no centre be eventually full of matter and energy?

Occam
2007-Jul-15, 11:48 PM
When reading that article, just mentally insert the word known in front of Universe and all will be well. Our knowledge of the universe, including its estimated age, is being revised all the time. I doubt very much if the 13.2 billion year figure will last and it's discoveries like this that help adjust the figure.

danscope
2007-Jul-16, 03:52 AM
Well said, Occam! Truer words were never spoken. In matters of knowledge,
we shall ever press on. A new page,...and a new day.
Best regards, Dan

thothicabob
2007-Jul-16, 05:44 AM
Thanks speedfreak! But I have a sort of handle on that anyway, but I'll check out the link. As i recall, however, the current estimate of the diameter is about 156 billion light years - yours is big; this is mind-boggling.

I'm fairly certain there are areas of the universe forever inaccessible to us - certainly the 300,000 light-year superluminal "head start" that inflation provided before things condensed and the radiation we see from the CMB was emitted was enough to put some degree of separation between 'us' and 'most' of the rest of the universe - and anywhere within this 156 bly "sphere", any observer would only be able to see "out" about 13.2 bly (at least, that would be their max visible horizon), if I understand it right. In essence, the 'known' (or visible) universe is really just a very small subset (at most) of what theoretically, at least, is "out there".

speedfreek
2007-Jul-16, 06:12 PM
Having seen some of the comments since my last post I feel it is my duty to point out the difference between inflation and metric expansion, just to confuse things a little!

Basically, the "inflationary epoch" is an event hypothesised to have happened within the first second after the big-bang. It had a duration of a fraction of a second, and in this time, the universe inflated from microscopic to macroscopic, ending up only a few centimetres across (an increase in volume of a factor of 10^78 or thereabouts!). Apart from this very small inflationary epoch, everything else (all other increases in distance) is due to metric expansion.

Now on to your figure of 156 billion light years. It is one of the common misconceptions that was widely reported but is in error. How it came about was thus:

Research using the WMAP data was used to extrapolate a minimum comoving size for the observable universe. This minimum size is 78 billion light years in diameter. This means that the comoving diameter of the observable universe should be a minimum of 78 billion light years. Unfortunately, in some media reports this figure was taken as a radius and thus the figure is was wrongly reported to be 156 billion light years in diameter.

But our best estimate so far puts that radius at around 46 billion light years, and so the diameter is 92 billion light years across (which is indeed larger than the minimum estimate from WMAP of 78 billion light years across). And this is all relating to the observable universe. We have no notion of how large the whole universe might be, the parts outside our observable universe.

thothicabob
2007-Jul-16, 07:17 PM
Research using the WMAP data was used to extrapolate a minimum comoving size for the observable universe. This minimum size is 78 billion light years in diameter. This means that the comoving diameter of the observable universe should be a minimum of 78 billion light years. Unfortunately, in some media reports this figure was taken as a radius and thus the figure is was wrongly reported to be 156 billion light years in diameter.

But our best estimate so far puts that radius at around 46 billion light years, and so the diameter is 92 billion light years across (which is indeed larger than the minimum estimate from WMAP of 78 billion light years across). And this is all relating to the observable universe. We have no notion of how large the whole universe might be, the parts outside our observable universe.

Okay, just to be sure I interpret what you're saying correctly, this means that galaxies we currently "see" as being 13.2 bly from us (within our visible horizon) based on their red-shift (meaning this is how long/the total distance the light's been travelling to reach us, not necessarily how far the galaxies were when the light was emitted) are "now" actually 46 bly away; Further, this represents likely a small fraction of the 'total' universe, much of which was separated sufficiently initially through inflation so that it's forever beyond our visible/knowable horizon, and metric inflation has served to accentuate this separation over time.

...a fair summation?

BTW, have you a link for the above? (I'll look for my own based on your info, but it would be useful to know what info you're working from. I'll admit, after reading the initial 'news' reports, and the associated paper, I haven't followed that particular topic up much).

speedfreek
2007-Jul-16, 10:46 PM
Okay, just to be sure I interpret what you're saying correctly, this means that galaxies we currently "see" as being 13.2 bly from us (within our visible horizon) based on their red-shift (meaning this is how long/the total distance the light's been travelling to reach us, not necessarily how far the galaxies were when the light was emitted) are "now" actually 46 bly away; Further, this represents likely a small fraction of the 'total' universe, much of which was separated sufficiently initially through inflation so that it's forever beyond our visible/knowable horizon, and metric inflation has served to accentuate this separation over time.

...a fair summation?

BTW, have you a link for the above? (I'll look for my own based on your info, but it would be useful to know what info you're working from. I'll admit, after reading the initial 'news' reports, and the associated paper, I haven't followed that particular topic up much).

Firstly, here (http://en.wikipedia.org/wiki/Observable_universe) is a wiki link that sums it all up nicely.

You summation is correct in principle, but I should point out that the terms are inflation and metric expansion - it helps to avoid too much confusion! ;)

thothicabob
2007-Jul-16, 11:03 PM
Firstly, here (http://en.wikipedia.org/wiki/Observable_universe) is a wiki link that sums it all up nicely.

You summation is correct in principle, but I should point out that the terms are inflation and metric expansion - it helps to avoid too much confusion! ;)

That must have been a fruedian slip - oopsies! - i've got the difference between inflation and expansion more or less down, i think. And I did find that link - I suspected that was the one you were referring to. Wikipedia can be a good source of info, but one must be careful, especially laymen like me, with using it; often there are errors that it would take an expert to spot. I've seen that with subjects I'm a bit more up on, and they can be pretty subtle...and important. Still, it's good as an initital reference and as a jumping off point, for sure.

thanks.

transreality
2007-Jul-16, 11:06 PM
Having seen some of the comments since my last post I feel it is my duty to point out the difference between inflation and metric expansion, just to confuse things a little!

Basically, the "inflationary epoch" is an event hypothesised to have happened within the first second after the big-bang. It had a duration of a fraction of a second, and in this time, the universe inflated from microscopic to macroscopic, ending up only a few centimetres across (an increase in volume of a factor of 10^78 or thereabouts!). Apart from this very small inflationary epoch, everything else (all other increases in distance) is due to metric expansion.



The size of the entire universe after inflation you mention is several centremetres across, yet metric expansion is referring only to the size of the observable universe. Where did the disjunction occur? Where is the uncertainty about the extent to which the observable universe and entire universe arising from?

speedfreek
2007-Jul-17, 01:12 AM
I am stating things as the current best model in cosmology proposes them, the wiki link was just for convenience. I know how some wiki articles can be misleading and should not be trusted without checking their references, but the whole big-bang section (check the side-bar) is pretty rigorously reviewed in my opinion. The comoving figure of around 46 billion light years to the edge of our observable universe is the current best estimate.

For Transreality: Even the inflationary epoch is described only as part of our observable universe, which inflated to a few centimetres across (I should have been more specific in my earlier post). The whole universe might have been a kilometre or 10,000 light years across after inflation (insert arbitrary figure as applicable!), but our observable universe was only a few centimetres across at that time.

thothicabob
2007-Jul-17, 01:22 AM
I wonder how long it will be before they find a galaxy older than the universe. Anyone taking bets?

Well, without pointing out the obvious (but it's related to how the ages of the galaxies and universe are determined), I'd be willing bet that will be a very long time indeed. ;o)

BigDon
2007-Jul-17, 06:21 AM
Wow. Just wow.

Thank you Speedfreak. (Boy, I sure hope your not one for real)

speedfreek
2007-Jul-17, 05:41 PM
Heh, the term speedfreak doesn't have same connotations in the UK as it does in the US. I also chose to distance myself from the US connotation by spelling it as freek and it all comes from my long love of motorsports!

It just happens that redshift and the metric expansion of space are the topics I have studied the most over the years.. I have only an amateur self-education in these areas of cosmology, but I have been keeping up with developments in these areas since I was a teenager in the early 1980's!