Recent Discovery of Galaxy + Black Hole

[BertiWooster]

I read recently that astronomers have discovered a giant galaxy surrounding the most distant supermassive black hole ever found .
The cluster of stars are so far away that it is being seen as it was 12.8 billion years ago � i.e the light from this galaxy , reaching us now, started out on it's journey 12.8 billion years ago . ( that is mind boggling to me , to put it midly )

Dr Tomotsugu , states that this galaxy and black hole ,must have been formed very rapidly in the early universe .

We are looking therefore at part of the early universe , soon after the 'big bang'
( my words )

Am I correct in the following -

1. At the big bang , the universe expanded rapidly at a rate far outstripping the speed of light .

2.Therefore the reason the light from these stars / the early universe , is only just reaching us is that the earth was formed and is thererfore at a distance in the universe , billions of light years from the location of where these stars are / were / were formed, themselves .

If I'm not correct please explain in easy to understand language � I'm trying to get my head around the fact that we are observing events 'soon' after the big bang .

[jake-the-peg]

1/ This is the general belief - it's called the inflationary stage and was pioneered by Alan Guth if you wan't to look it up

2/ Yes and obviously the expansion of the universe continued to seperate the two bodies contributing to the delay.

Note also that the farther away two bodies are the faster they are receding from each othe. This is because the Universe itself is expanding so where there is more "Universe" between us there is more expansion and a faster recession.

You would not see this if it were just a giant explosion into an empty Universe the way that the Big Bang is sometimes niaively pictured

[jake-the-peg]

BTW what's interesting here is the fact that this Galaxy was formed so quickly after the big bang.

With existing theories it's difficult to show how we get from a super energetic early Universe where matter is starting to form to island galaxies like we see today.

There is a lot of stuff like dark matter and dark energy that we don't yet understand enough to properly show how this happened.

Consequently finding really early examples of these is of great interest

[BertiWooster]

Thanks for that jake

It's incredible that ( even allowing for the fact that the continuing expansion of the universe is contributing to the dealy ) when the light from this galaxy started it's journey - it would have been another 8 billion years or so before the earth was born.

Is the reason that we cant quite see back, nearer to the big bang , because the light has already gone past ?

How do astronomers know/ measure that this light has been travelling for this period of time ?

[jake-the-peg]

Yes we think there is an Event horizon past which we cannot see because of this.

How we know the distances to stars and galaxies is an interesting story.

We first measured the distances to the nearest stars by the amount that they seem to move (their "paralax") due to the Earth going around the Sun.

For a long time though nobody was quite sure how far away galaxies were. Then Edwin Hubble discoverred the red shift. When you look at the spectrum of light from a star it contains black "Fraunhoffer" lines that tell you about the elements present. If something is moving away from you very fast these appear shifted into the red by the doppler effect.

What Hubble managed to do was to find specific stars called Cepheid variables in nearby galaxies. These are variable in their brightness but very special because that brightness is linked to their period of intensity. Measure their period you know who bright they should appear at say 1 light year. Compare that to how bright they really seem and you know how far away they are.

So Hubble found that a) Galaxies were a very long way away and b) there was a relationship between this red shift and their distance.

So we can measure the redshift of any distant body like this and know how far away it is and how early it is.

There's some toing and froing about the exact figures, the so called Hubble constant but in a nutshell that's it.

[beso]

Much of the Universe has already disappeared over the horizon.

The space between us and the most distant objects has expanded. Even though the light should have had time to reach us the distance subsequently became further and the light has still not reached us.

[BertiWooster]

I find this subject facinating .

Do we know how fast the universe is expanding compared to the speed of light ?

[jake-the-peg]

80 Km/sec per MegaParsec is the best guess ( A megaparsec is 3.3 Million light years ).

You recall I said things recede faster the further away they are from us because space is expanding. Well for every MPc away it's an additional 80 KM/sec.

So this object 12.8 billion Light years away is pretty close to the speed of light.

The thing is not to think of it as a baloon that's expanding but more like currents in a loaf of bread that's rising. Every morsell of bread is expanding so the more morsels between raisens the faster the seperation speed

[rov1200]

http://www.space.com/scienceastronomy/090817-dark-energy-alternative.html

If you don't believe the universe is expanding you can take another view

[jake-the-peg]

I think you'll find the Big Wake idea still has an expanding Universe it's just not accelerating in a manner that suggests dark energy.

Although I think Big Wave needs to show it can explain what we already observe before getting all excited.