Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Slawomir Budziak on 29/04/2011 13:30:06
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Slawomir Budziak asked the Naked Scientists:
Dear Scientists,
How deeply into the history of the universe can we currently see using telescopes?
Your faithful Polish listener (http://www.thenakedscientists.com/HTML/podcasts/),
Slawomir Budziak
What do you think?
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Using radio telescopes it is possible to get back to a few hundred thousand years after the big bang by observing the cosmic microwave background. Beyond that point no observations by electromagnetic radiation are possible because the universe was not transparent. there are two other thresholds that may be eventually reached by using first neutrino telescopes to measure the neutrino background radiation and finally gravitational wave telescopes to see the very beginnings of the expansion itself. however observations of other effects do allow us to infer conditions before the CMB namely the proprtions of hydrogen helium and other atoms in the oldest material etc but these are not really telescopes just fossil evidence.
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Hello Soul Surfer and other forum users. I will take the liberty of quoting the full question I sent to the Naked Scientist. I am struggling to put two pieces of information together in such a manner as to have a coherent picture of our state of knowledge about the universe.
The first bit of information concerns the oldest galaxy which, as I learnt from a scientific radioprogram, had been discovered the the Hubble telescope and dates back to 480 million years after the big bang. The galaxy in question is thus over 13 billion years old.
The second element of this puzzle is the claim made by one the scientists working with the SKA radio-telescope which went more or less as follows: „If you were to draw a ruler out into the universe, from where we are today (point 0), the furthest point where we can see today is 1." and with the SKA "we would like to be looking at 10 (…) the point in the history of the universe where the very first objects formed“.
@Soul Surfer - your post correlates very well with the first bit of data I referred to. How does the second one fit into the picture?
regards
Slawomir Budziak
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The SA telescope is expected to reach 50-100 times further than any existing radio telescope. The idea behind it is to use a lot of smaller radio telescopes and then put their radio-images together, in real time, into one big picture, also called interferometry.. (http://www.nrao.edu/index.php/learn/radioastronomy/radiotelescopes). Australia or South Africa is thought to be where it gets built finally, but in SA Shell wants to explore after oil, in the same region planned for SKA, so it is still a open bid what the South African government choose. Depending on their need for quick money or a long time development it will be one or the other.
If it will see the absolute beginning? Nah, don't think so myself, but it will be very close to it. The square kilometer array telescope. (http://www.skatelescope.org/uploaded/37504_080924_URSI_Hall.pdf)
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The SA telescope is expected to reach 50-100 times further than any existing radio telescope. The idea behind it is to use a lot of smaller radio telescopes and then put their radio-images together, in real time, into one big picture, also called interferometry.. (http://www.nrao.edu/index.php/learn/radioastronomy/radiotelescopes). Australia or South Africa is thought to be where it gets built finally, but in SA Shell wants to explore after oil, in the same region planned for SKA, so it is still a open bid what the South African government choose. Depending on their need for quick money or a long time development it will be one or the other.
If it will see the absolute beginning? Nah, don't think so myself, but it will be very close to it. The square kilometer array telescope. (http://www.skatelescope.org/uploaded/37504_080924_URSI_Hall.pdf)
Open bid! Your having a laugh. I can totally guarantee that this area will be sold out to oil. It is the nature of greed over science.
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The SA telescope is expected to reach 50-100 times further than any existing radio telescope. The idea behind it is to use a lot of smaller radio telescopes and then put their radio-images together, in real time, into one big picture, also called interferometry.. (http://www.nrao.edu/index.php/learn/radioastronomy/radiotelescopes). Australia or South Africa is thought to be where it gets built finally, but in SA Shell wants to explore after oil, in the same region planned for SKA, so it is still a open bid what the South African government choose. Depending on their need for quick money or a long time development it will be one or the other.
If it will see the absolute beginning? Nah, don't think so myself, but it will be very close to it. The square kilometer array telescope. (http://www.skatelescope.org/uploaded/37504_080924_URSI_Hall.pdf)
Yoron - the SKA might allow for better resolution, but as we can already identify the CMBR we will not be able to go "back" any further. The CMBR / Surface of last scattering is the EMR limit of perception; before then the entire universe was opaque. So to re-iterate SoulSurfers point - we are already at the time limit of what we can see with EMR telescopes. New telescopes like the SKA will improve our views of the early universe but not push back further into the past
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The square kilometer array is specifically designed to look at red shifted 21cm hydrogen radiation. This is radiation produced in a hyperfine interaction between the proton and electron of a cold hydrogen atom and can detect the presence of clouds of hydrogen before they form stars and galaxies. This will allow the detection of forming galaxies in the "dark ages" of the universe before many stars had formed and will give a significant extension of structural information in our universe and allow our models to be examined in more detail for accuracy.
Now you are thinking of measuring distance in terms of light years and clearly going ten times further than 13 billion light years is not sensible so the distance scale has not been defined in these terms. The scale being used is a different one based on a non linear scale. On this scale red shift is often used a red shift of 1 is a bench mark this means that the light has twice the wavelength or half the frequency that it was emitted at when we see it this turns blue light into red light (hence red shift) now the cosmic microwave background was emitted when the whole universe was about at the temperature of the surface of a star, that is around a red shift of 1000. So there are several factors of ten to go on this distance scale.
Now current observations of the neutral hydrogen line are not as great as optical telescopes and probably limited to around a red shift of 1 so going to a red shift of 10 where the 21 cm (1.4 GHz) radiation becomes 210 cm (140 MHz) represents a significant increase in range out to and beyond the current observations. Furthermore these observations will give a detailed broad picture of this structure instead of the few fortuitous gravitational lenses or voilent events that allow very remote objects to be observed.
Why use a non linear scale well the detail of what is happening become much smaller as you push further back towards the big bang when things are very hot and events happen very quickly se when the cosmic microwave background was formed our universe was only around 380,000 years old and trying to definre that in the context of 13 billion years from our viewing point just does not make sense defining it only in time from the big bang disconnects it from our now however using the red shift scale it works all the way as far as you can go.
The very first stars probably formed at redshifts of 20 -100 and some of the violent gamma ray bursts may be associated with them.
Beyond a res shift of 1 almost everything has to be done using models and "fossils" like the ratio og=f hydrogen to helium in the earliest stars
It is interesting to note that there are two other background radiations that may one day be observed
1 The Neutrino background at a red shift of around 10^10 a couple of seconds after the big bang showing structure around the time nuclei were forming.
2 The gravitational wave backrround at 10^25 which could confirm details of inflation .
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Very interesting Soul Surfer. And yeah Imatfaal, CMB may define the absolute start, but we will see further with this telescope as I understands it? how far I don't know though? But Soul Surfers explanation makes it almost understandable :) What fascinate me is the how they can guarantee a 'real time' interpretation of all that data. That must be a incredible amount of information that you will need to integrate into one picture.
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Further in time btw. That seems to be what you reacted on, and that's what Soul Surfer points out too. That we will come closer to the BB, but not by using it as 'visual' binoculars. But, it's still a search for the faintest light as I understands it, and so, in that motto, possible to define as reaching further out. The 50 to hundred times further, is a definition you will find at a lot of sites and using the definition of detecting the faintest light it will reach further, enabling us to see red shifted objects outside our radio telescopes resolution today.
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Yor-on; No we cannot see past the CMB using electromagnetic radiation and the SKA will not do this it is just that they are using a non linear distance /time measurement based on the red shift which is as follows,
Red shift 1 10 100 1000 ***** 10^10 infinity
measure
Light years a few billion 13.7 billion- 370 000Y 13.7 bill -2 seconds 13.7billion
from here
objects dist galaxies most dist galaxies first stars Microwave background nucleii big bang
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SoulSurfer - the maximum angular resolution of an optical telescope relies on aperture and wavelength of light - I presume radio telescopes have a similar limitation with reference to the wavelength and area (or sqrt of) of the aerial (?) or something like that.
How would this work with neutrinos? Would a neutrino's wavelength (what is this anyway) get extended by redshifting - or are we talking a different method of reduction of energy? And graviational waves would be very high wavelength any way - would they be stretched even further by the time we receive them?
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No Soul Surfer, didn't mean pass the CBM, just further away in time, and so more distant. The more red shifted a object is, the further away it will be distance wise too, generally speaking, as I understands it? Or am I thinking wrong there?
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What I was thinking there was that the waves/redshift we discuss are expected to have a source. But I think I see how you mean :) and it was a lovely presentation of how the redshift relates to age. Thanks for that one. I think it's a incredible achievement if we succeed in getting it to work. Will be a big feather in the hat for any country getting this project. SA will be stupid if they choose oil before it.
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Yoron - to get further away in time or in distance, you need light that has travelled for longer than that of the CMBR and there is none! The SKA will allow us to see the first stellar formations and early galaxies in unprecedented detail - but these events are way more recent than the era that caused the CMBR. You can think of it as the universe being in a state of "white-out" till the era of last scattering, then almost completely dark (ie no new photons emitted) whilst the atomic hydrogen slowly gathers together, then stars slowly burst into life and there is new emission of photons again.
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ah well, can't sleep anyway :) It's a weird thing, if we assume a inflation and look out in the universe those 'light sources' should actually have been placed isotropically everywhere around us, and closer than they are today. so what we might see could be the light before the star formations, and also as they get formed I assume? On the other hand, that light we see from those moments should be extremely red shifted, and that should mean that it's very old light, if I'm thinking right. And with age comes distance as I think of it, that is any red shifted light you measure today will have to have traveled further than the less red shifted light you measure. We can see approximately 9.6 billion light years away today as I understands it? But with light coming from when the first stars was created? It seems as if free electrons created in the 'plasma'? becomes a screen obstructing the view a couple of hundred thousand years after the Big Bang but I believe that it will be able to see the light from the first stars and they, if still existing, has to be awfully far away from us today, assuming a expansion?
And that was also what I mean by the 'light sources' in my first post. But thinking of it I saw that we also might see the light before those stars was formed and I can see how you think there. But what light you measure from the CMB today here have traveled just as far in time as it is old actually. That the plasma was isotropic just mean that it was evenly placed everywhere in space but as measured today from any point in SpaceTime that background radiation should have traveled the amount of years it is old. So I still find my reasoning reasonable :) Or am I thinking wrong there? The CMB is red shifted but only through the expansion, whereas with a star receding it can be both expansion and its own motion from us creating the absolute redshift we measure. Da*n
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Another thing, if we somehow could see past that electron cloud would we possibly be able to see the universe shrink? That made my head spin when I thought about it :) That's not possible is it. To see the hydrogen plasma? I better try to get some sleep here :)
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Rereading you, is it the recombination period you discuss? And no free photons propagating? You mean that they got scattered colliding with electrons and protons and so give no clear picture under that period? Or was there something more to it?
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ah well, can't sleep anyway :) It's a weird thing, if we assume a inflation and look out in the universe those 'light sources' should actually have been placed isotropically everywhere around us, and closer than they are today. so what we might see could be the light before the star formations, and also as they get formed I assume? On the other hand, that light we see from those moments should be extremely red shifted, and that should mean that it's very old light, if I'm thinking right. And with age comes distance as I think of it, that is any red shifted light you measure today will have to have traveled further than the less red shifted light you measure. We can see approximately 9.6 billion light years away today as I understands it? But with light coming from when the first stars was created? It seems as if free electrons created in the 'plasma'? becomes a screen obstructing the view a couple of hundred thousand years after the Big Bang but I believe that it will be able to see the light from the first stars and they, if still existing, has to be awfully far away from us today, assuming a expansion?
And that was also what I mean by the 'light sources' in my first post. But thinking of it I saw that we also might see the light before those stars was formed and I can see how you think there. But what light you measure from the CMB today here have traveled just as far in time as it is old actually. That the plasma was isotropic just mean that it was evenly placed everywhere in space but as measured today from any point in SpaceTime that background radiation should have traveled the amount of years it is old. So I still find my reasoning reasonable :) Or am I thinking wrong there? The CMB is red shifted but only through the expansion, whereas with a star receding it can be both expansion and its own motion from us creating the absolute redshift we measure. Da*n
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Another thing, if we somehow could see past that electron cloud would we possibly be able to see the universe shrink? That made my head spin when I thought about it :) That's not possible is it. To see the hydrogen plasma? I better try to get some sleep here :)
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Rereading you, is it the recombination period you discuss? And no free photons propagating? You mean that they got scattered colliding with electrons and protons and so give no clear picture under that period? Or was there something more to it?
Don't like the name "recombination period" it presupposes a period of combination and destruction before which do not exist. But yes, the era that was c 370k years after big bang which starts with a mess of protons, ions, electrons, and radiation that is opaque and ends with a boring dark very spaced out cloud of hydrogen/helium atoms.
To tackle your first/second paragraph is gonna be hard.
The light we see from the era of last scattering/recombination era is very red-shifted (factor is over a 1000) that from the earliest stars is much less redshifted. We can see 13.6 billion years into the past (cos we can see the CMBR) - but due to universe expansion that is now 46 billion light years distant from us.
The furthest/oldest stellar objects we can see are around 13.1 billion years old - http://arxiv.org/abs/1010.4312 about 30 billion light years away, and are red-shifted by 8.55. As near as anything this is the light of the first stars. As you can see it is younger, closer and less red-shifted that the CMBR.
Between the end of recombination/last scattering, and the genesis of the star there was NO new light formed - this was the universal dark ages.
The ionized matter that formed the CMBR was moving away from us very rapidly AND it has had huge amounts of redshift from universal expansion. Stars may be moving very quickly but the amount of redshift from expansion is many times smaller.
I hope thats getting clearer. If not youre gonna have to ask simpler questions - or rope in a real cosmologist like ssurfer
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Heh, he is checking on us :)
Okay, I will have too look at the pdf :) but I presume that this a radio telescope? I'm looking on the resume as I write and seeing that it's about ionizing Ly-alpha photons I guess this -Astronomers Find 90% More Universe.- (http://www.universetoday.com/60773/astronomers-find-90-more-universe/) will fit admirably.
"Astronomers frequently use the strong, characteristic “fingerprint” of light emitted by hydrogen known as the Lyman-alpha line, to probe the amount of stars formed in the very distant Universe Yet there have long been suspicions that many distant galaxies go unnoticed in these surveys. A new VLT survey demonstrates for the first time that this is exactly what is happening. Most of the Lyman-alpha light is trapped within the galaxy that emits it, and 90% of galaxies do not show up in Lyman-alpha surveys."
I found it a very interesting piece of discovery, if it is correct? And yeah, I get slightly confused, as I did look for the furthest visible object, just finding this -Galaxy cluster at the edge of the Universe.- (http://blogs.discovermagazine.com/badastronomy/2010/05/10/galaxy-cluster-at-the-edge-of-the-universe/) as the farthest? But that pdf place it a he* of a way further. It must have to do with how I defined the search I guess. I hope we're doing okay so far Soul Surfer? :)
If we're not you better step in and correct it.
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Hubble space Telescope, not radio then?
That's pretty far away.
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No not radio - it is redshifted from ultraviolet where the lyman-alpha line lies to the near infra-red (1200 Ang to 11000 Ang). We use radio telescopy not so much because everything is redshifted and we have to - but because intervening stuff is transparent to radiowaves, we can use radio interferometry, and object emit radiation at long wavelengths as well as short