NASA Discovers Most Distant Galaxy In Known Universe 105
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."
I don't get it (Score:5, Interesting)
Apologies for the ignorance - So I understand that the further an object is the longer it takes for light to reach us. So what we observe is effectively light that has been traveling for a long time and we are looking back in time. But surely the Universe is expanding and is we go back in time then at some point we were in fairly close proximity to this galaxy. Light back then would have taken only a few moments to reach us. Moving forward from this point, for us to be able to see the past now surely we must have moved away from this galaxy at a relative speed that is considerable. What I don't get is how fast we need to be hurtling away from this galaxy for us to see the relative past now. As surely any speed below the speed of light would only slow time, rather than reverse it as implied here. Can anyone explain?
Re:I don't get it (Score:3, Interesting)
Consider two objects moving vertically from one another (along the x axis, and along the y axis), or in the same direction at different speed, or in opposite directions. At some point, light from the first will need a year to reach the other; what the other will then see is what the first looked like a year before.
Re:I don't get it (Score:5, Interesting)
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.
However 420 mln light years after the Big Bang, was the universe already that big? If the universe was smaller (say 1 bln light-years across) the light of that star system should have reached us long time ago.
And, on the same note, there must be a lot of our universe that we can not see, simply because it is now so far away from use that the light from those places can not have reached us yet.
Or are OP and me missing something? If so, what?
Re:13.3 billion in one direction? (Score:2, Interesting)
The radius of the observable universe is 45.7 billion light years ( http://en.wikipedia.org/wiki/Observable_universe ). So yes, if you take 2 objects in opposite directions they are seemingly receding much faster than the speed of light in relation to each other. This does not violate relativity because it is actually the spacetime fabric that is expanding.
The 13.3 billion quoted here is actually the distance that light traveled to get here. The universe has been expanding all this time, therefore this galaxy's current proper distance is at around 43 billion light years.
NASA doesn't discover galaxies: astronomers do (Score:5, Interesting)
I realise that the title of this article was carried over from the CBC article, but could we at least try to remember that it's astronomers that discover things like this high-redshift galaxy, not an administration like NASA in isolation? I don't mean to diminish the absolutely central role played by NASA in both Hubble and Spitzer, of course, but at the same time, a whole range of people, institutions, and organisations come together to make scientific discoveries like this possible, and I think it's important that we recognise that science is often a highly collaborative and international endeavour.
For example, there are 23 astronomers who co-authored the paper on this galaxy: 11 are from US institutions, 11 from European institutions, and 1 from a Chinese one. Note, I didn't say that they were (necessarily) American, European, and Chinese: in the list of co-authors, there are at least some Europeans working in the US and vice versa.
Also, the Hubble Space Telescope is a collaboration between NASA and ESA, the European Space Agency, albeit with NASA in this instance contributing the majority. There are other space missions including Herschel and Planck which are led by ESA, but in which NASA plays a minority role. Many space missions are collaborative in this way, in essence underpinning the mix of US-based, Europe-based, and other international astronomers who've written this paper.
In more detail, it can get even more complicated when you realise that NASA, ESA, and other space agencies themselves employ astronomers and other space scientists, so in that sense, discoveries can be made by those organisations too.
Speaking of which, it might have been more appropriate to give the links to the original US and European press releases from the Space Telescope Science Institute [hubblesite.org], NASA [nasa.gov], and ESA [spacetelescope.org] to get the full story.
Anyway, despite the (important, I believe) pedantry, this is is an interesting discovery :-)
Re:I don't get it (Score:4, Interesting)
That part I get; I also checked the wikipedia link provided by a helpful AC.
The issue I don't understand: this galaxy must have been some 13.3 bln light years away from us, as the light took that long to reach us. Anything closer we'd see "nearer in time". This means the galaxy must have been at least that big already at that time. Sounds pretty big to me, considering it has been expanding since and expansion is accelerating.