NASA Discovers Most Distant Galaxy In Known Universe

An anonymous reader writes with this snippet from cbc.ca: "'NASA's Hubble and Spitzer space telescopes (not to be outdone by the Kepler Space Telescope) have discovered the most distant galaxy identified so far in the universe... the galaxy is 13.3 billion light years away and only a tiny fraction of the size of the Milky Way. Due to the time it takes light to travel through space, the images seen from Earth now show what the galaxy looked like when the universe was just 420 million years old, according to a press statement released from NASA. The newly discovered galaxy (is) named MACS0647-JD."

Re:I don't get it

[Anonymous Coward]

This is explained thoroughly on http://en.wikipedia.org/wiki/Observable_universe

Re:I don't get it

[gshegosh]

The speed limit of c only applies to matter inside of the spacetime. The spacetime itself can expand faster than light and in fact there might be galaxies that we'll never be able to reach or see because they move away from us faster than light. Moreover, the idea of inflation stage of universe growth seems to explain well some problems with standard "big bang" theory and is widely accepted. Inflation means that there was a shot period in universe history when it expanded very quickly, faster than light speed in fact.

Re:13.3 billion in one direction?

[meetpi]

It's also worth pointing out that in the context of the universe, there is no edge. By default we tend to think of the universe as being like an explosion in space where the first particles ejected are at the edge of the explosion radius.

However, when we're discussing the universe, this explosion is actually creating space, so the expansion is not from the core to the edges, it's happening through all of space - everything is moving away from everything else. Think of it like the surface of a balloon that is being blown up. In 2d terms, all points on the surface of the balloon are moving away from each other, but none of them are at the 'edge' of the balloon.

Someone standing on the surface of a sufficiently large balloon would look around and see everything receding from them - it would be reasonable for them to feel they were at the centre of the surface of the balloon and that therefore somewhere there was an 'edge' - but they'd be wrong.

Re:13.3 billion in one direction?

[aneroid]

Would the distance between the two galaxies be 26.6 billion years and longer than the age of the universe?

Good point: Yes and No.

Would it happen, yes, already has: If the universe is 93 billion light years in diameter, it is obviously possible to to find a galaxy 26.6 billion light years away but it should not be older than 13.7 billion years.

Because 13.3 billion light years away vs 13.3 billion years ago are not the same in the "Expanding universe" theory. The summary says "the galaxy is 13.3 billion light years away" - which makes it not as old as that statement implies --- imagine an early universe 1 billion light years across, with 2 galaxies forming near the edge diametrically opposite each other. They could now be 93 billion light years apart from each other but they would still be slightly younger than this one (MACS0647-JD). Similarly, it's possible that this galaxy could have been formed 12 billion years ago and has since moved relatively or "apparently" further away to 13.3 billion light years. 1.3 billion light years in 1.3 billion years in an expanding universe doesn't seem impossible since the universe is already larger (93 billion light years) than it is old (13.7 billion years).

The article didn't explain how they've correlated distance with age. Doppler shift?

The "No" part to your question, and the part which makes some of my answer wrong, is for observable:
There would also be the implication that what is "observed" can not be older than 13.7 billion years so you would need to wait another 13.3 billion years to observe the 13.3 billion year-old galaxy **at** 26.6 billion light years away.

Re:I don't get it

[Kergan]

I think the point of OP is different: the light from this galaxy took 13.3 bln years to reach us; so this implies the light has been travelling for that distance (13.3 bln light-years) before it reached us. Otherwise it should have reached us earlier. (...)

Or are OP and me missing something? If so, what?

I suspect you're misunderstanding space inflation. The big bang wasn't so much an explosion in space than it was an explosion of space. Picture a balloon with dots on it. Roughly speaking, our 3d space would correspond to the balloon's surface. (The balloon's volume corresponds to nothing physical.) There isn't such a thing as a center of the balloon's surface any more than there is a center of the universe, and the big bang corresponds to a huge initial blowing into the balloon. Crunchy details if needed [ucr.edu].

Re:I don't get it

[History's Coming To]

It's a perfectly good question, and a tricky one to fully explain. The first thing to look at is how you measure distances - because we're talking about light here we're firmly in the realm of relativity, so there's no such thing as "space" and "time", you have to bundle them together in spacetime. And talking of x-light-years or y-million-years doesn't actually make much sense, you have to measure both at once, so instead of distances or times things are measured in "spacetime intervals" which account for all four dimensions.

Now this is the tricky bit - for any "light-like" path (more technically called a "null geodesic") the spacetime interval is zero. So the light that we're receiving from the galaxy here and now has a spactime interval of zero. The light that this galaxy emits all travels the same spacetime interval of zero - some of those photons would have been aimed at (as you suggest) "our galaxy" when it was "closer" - although in fact "our galaxy" was just a wisp of hydrogen at the time. Other photons (the ones we see today) were essentially aimed at a point that was also 13Bn years IN THE FUTURE, and those are the ones we see hitting us today.

Long story short, you don't just aim light at a point in space, you also aim it at some point in the future, and the further away in space it's aimed then the further into the future it's aimed. In a million years we'll still be able to see this galaxy (assuming it doesn't slip over the cosmic horizon), and the photons we'll detect then are currently still in transit, aimed at when/wherever we will be then, just as the photons we detect today were still in transit last week, last year and 13Bn years ago.

Re:Very young galaxy

[History's Coming To]

It's exactly at the point of the Big Bang. As are you. As is Jupiter, Spica, and an empty bit of space a billion lightyears from our galaxy. The Big Bang happened everywhere, it's just that "everywhere" was all in one place at the time.