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Galaxies Distances

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Galaxies Distances was created by disley

If the Milky Way formed at about the same time as recently discovered
deep space galaxies why are they 12 billion light years apart?
16 years 11 months ago #23434

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Replied by voyager on topic Re: Galaxies Distances

If the Milky Way formed at about the same time as recently discovered
deep space galaxies why are they 12 billion light years apart?


Becuse they formed in different places I would guess. I'm not entirely sure what exactly you mean though.

Bart.
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16 years 11 months ago #23437

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Replied by disley on topic Re: Galaxies Distances

The Universe started small and expanded I understand but not at 12 billion light years speed?
16 years 11 months ago #23442

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Replied by voyager on topic Re: Galaxies Distances

The Universe started small and expanded I understand but not at 12 billion light years speed?


What do you mean "12 billion light years speed"? The universe has been expanding for 14 billion years .... why can't things be 12 billion lighyears appart?
My Home Page - www.bartbusschots.ie
16 years 11 months ago #23445

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Replied by disley on topic Re: Galaxies Distances

I understand the universe is speeding up all the time do you know at
what speed it is now?
16 years 11 months ago #23448

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Replied by Seanie_Morris on topic Re: Galaxies Distances

The Universe started small and expanded I understand but not at 12 billion light years speed?


That, actually, sounds correct. The Light Year (Ly) is only a measure of distance, though it also sounds like a measure of time. I'm not a cosmologist, so I can't comment on whether the 2 are linked in your scenario, but certainly thinking about it does seem to suggest so.

Don't forget disley, as we are currently looking at it, we see those distant galaxies 12 billion Ly away as they were 12 billion years ago. They have sinced moved from their 'last known position', and where they are now can ge guestimated by following whats called 'redshift'. But thats for a different discussion. if we could stand where we are and look out into space 12 billion years ago, most of these galaxies would probably have looked like large, irregularly shaped star clusters against the night sky.

Seanie.
Midlands Astronomy Club.
Radio Presenter (Midlands 103), Space Enthusiast, Astronomy Outreach Co-ordinator.
Former IFAS Chairperson and Secretary.
16 years 11 months ago #23449

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Replied by dmcdona on topic Re: Galaxies Distances

I guess all three could have formed at the same time but have either formed in different places or have been formed in the same place and travelled in different directions.

e.g. if you and I set off from Liffey Valley and went along the M50 North and South respectively, the distance between us would increase even though we would be doing the same speed (10 km/h) :D

As far as I know, the visible universe extends to about 13.7 billion light years. But I read somewhere recently that the actual size is something like 40 billion light years - we just can't see it...

€0.02 worth from a similar non-cosmologist as Seanie
16 years 11 months ago #23452

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Replied by disley on topic Re: Galaxies Distances

more research on my part I understand the universe is expanding at or above the speed of light.If my Deep Sky galaxy and our Milky Way
are speeding apart will its image not speed towards us at the same speed?
16 years 11 months ago #23468

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Replied by DaveGrennan on topic Re: Galaxies Distances

more research on my part I understand the universe is expanding at or above the speed of light.If my Deep Sky galaxy and our Milky Way
are speeding apart will its image not speed towards us at the same speed?


Disley, have you come across the balloon analogy of the universe expanding. Its often used to explain why most galaxies appear to recede from us. draw two dots on opposite sides of a balloon and blow it up so it expands at the speed of light for 6 billion years, one dot has gone 6 billion light years in one direction, the other has gone 6 billion ly in the opposite direction although that balloon has only been expanding 6 billion years, the two dots are 12 billion ly apart?

That make sense?
Regards and Clear Skies,

Dave.
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16 years 11 months ago #23472

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Replied by disley on topic Re: Galaxies Distances

Yes re the baloon. 2 points what about the image?

I agree re 6 billion each way but would this not mean we see the Deep

Sky galaxy as it was 6 Billion years ago and not as in the Hubble photo

not long after the big Bang ?
16 years 11 months ago #23474

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Replied by dmcdona on topic Re: Galaxies Distances

My head hurts. I'm off for a lie down... :cry:
16 years 11 months ago #23478

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Replied by DaveGrennan on topic Re: Galaxies Distances

Yes re the baloon. 2 points what about the image?

I agree re 6 billion each way but would this not mean we see the Deep

Sky galaxy as it was 6 Billion years ago and not as in the Hubble photo

not long after the big Bang ?


That may be true if light could travel through the center of the balloon but it cant, space-time is curved therefore the light takes a longer time to get here. But your original question was;

why are they 12 billion light years apart?

Regards and Clear Skies,

Dave.
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16 years 11 months ago #23485

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Replied by ctr on topic Re: Galaxies Distances

While also not a cosmologist, is there not Hyperinflation soon after the big bang to take into account.

The furthest galaxies appear very red and therefore are moving the fastest away from us. I read recently that the spectrum of their stars contain very little heavier elements and so are first generation stars. So I suppose they are first generation Galaxies

One question that is needed to be confirmed is if the Milky Way is one of these first generation Galaxies? As we are here I guess not.


If any of the above is complete waffle please understand I'm having a long day. My knowledge on this subject is limited but, like disley, I find it fascinating.

Each of us is here on earth for a reason, and each of us has a special mission to carry out - Maria Shriver

16 years 11 months ago #23488

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Replied by albertw on topic Re: Galaxies Distances

Disley, have you come across the balloon analogy of the universe expanding.


I prefer the raisins in a cake analogy :-) You can have light go directly though (you are using transparent flour right?!) basically and raisin will see all the other raisins moving away from it as the cake expands in the oven. Though the universe is thought to be cone chaped and not cake shaped - (dont bother asking me to clarify that! I read it in Nature or somewhere like that in a paper on the WMAP data).

One thing to remember about the deep field images is that most of the prety galaxies are relativly close foreground ones. When astronomers talk about the galaxies that are say 12 billion years away, they are referring to the small smudges of light in the background.

The current speed of expansion is a big matter of debate. Redshift from galaxies outside our local cluster will tell you the current expansion speed over that distance. The change in that speed over time, or the acceleration of the universe is still a hot topic. Though its starting to be settled. They key to measuring acceleration lies with the Hubble Constant. The current value from satelite observations is 71±4 (km/s)/Mpc which is quite a surprise. It was long thought that the universe might constantly expand though decelrate, and perhaps even contract back to a big crunch. 71.4 would mean that the universe is accelerating in its expansion. If you do some reasearch on Hubble's Law you'll get a better understanding of the issues with the expansion of the universe. There are lots of ways of inderectly measuring the hubble constant, one brute force quantity over wuality approach is described in www.irishastronomy.org/user_resources/fi...20454-arc_jan_05.pdf

One school of thought is that the early universe did expand very very quickly. Thats what inflation theory is all about. The theory is needed to explain a couple of issues witht he big bang.

The HDF images were quite a surprise when they appeared. Prior to that there were few galaxies with a redshift of more than 1 known. Galaxies in the deep field go to a redshift of 6, which is where the 12 billion ly figure comes from.

The light horizon of the universe is about 14 billion ly. So from the earth we can see light from things up to 14 billion ly away. The same would go for any raisin in the cake! (forget about the crust). However the universe is much bigger than that, thanks to expansion (and inflation). Currently the universe is at least 40 billion ly wide, or at least 156 billion ly wide. Those numbers depend on dark energy, which I know next to nothing about, other than its thought to be responsible for accelerated expansion. Dark Energy is one of the current trendy topics in cosmology so in the coming years those numbers will be refined.

Seeing galaxies back to 12 billion ly should not be too surprising though. Afterall we have images of the cosmic microwave background which effectivly are images of the universe as it was half a billion years after the big bang.

Cheers
Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/
16 years 11 months ago #23506

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Replied by Maddad on topic Re: Galaxies Distances

For any of these numbers, 13, 40, or 156 billion light-years, we're talking about the radius of the universe as opposed to its diameter. Makes my head hurt to think about it because I'll never ride my bike that far.
16 years 4 months ago #32782

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