View Full Version : Hubble Finds One of the Earliest, Brightest Galaxies in the Universe

2008-Feb-12, 10:10 PM
By boosting the abilities of Hubble with a gravitational lens telescope provided by nature, astronomers have been able to peer back to the earliest times in the Universe; to see a galaxy just 700 million years after the Big Bang.

More... (http://www.universetoday.com/2008/02/12/hubble-finds-one-of-the-earliest-brightest-galaxies-in-the-universe/)

2008-Feb-13, 05:36 AM

If and when we obtain a reasonable head-count of galaxies this distance, and gain an understanding of their spectra, we will once again - for at least the third time in Hubble's life, learn that this bright standout is just one of many many galaxies, most of which are much dimmer, and very much like our own.

It is tantalizing to hope, or expect otherwise, but we know selection effects limit our prospective of the most distant universe, and until we gain enough light gathering power to count and quantify, we can only hope and guess. We will see the brightest of the most distant events first, then more an more routine galaxies.

Ken G
2008-Feb-15, 05:48 PM
Did anybody note this rather odd paragraph from the link identified as the "original source" (the Hubble news release):

Current theory holds that the dark ages began about 400,000 years after the Big Bang, as matter in the expanding universe cooled and formed clouds of cold hydrogen. These cold clouds pervaded the universe like a thick fog.
I can't help but wonder why they think that the dark ages "began" when hydrogen became neutral, and their choice of the word "fog" certainly makes it sound like it got dark because it was all shrouded in some thick dark fog like a foggy night. Of course that overlooks the fact that the universe was pervaded by a brightness approaching that of the Sun but from all directions during that epoch, and the formation of neutral hydrogen did not affect that "darkness" in any way, indeed it was much more like the lifting of a fog that allows us a view of that era. I guess it's just tricky passing astronomical information through the general media, but shouldn't a "Hubble new release" be of a fairly high standard of scientific precision?

2008-Feb-15, 05:58 PM

It's good of you to make a prediction here. I don't think the upgraded Hubble will show much more depth than we've already seen, but in less than ten years, we should be seeing some great images from JWST that will show your prediction to be right or wrong (not inconclusive).

The best we will get from Hubble at this redshift is a few more anecdotal examples seen through the lens of a Galaxy cluster. JWST will give us much more surface area, and much deeper IR sensitivity.

My prediction is more mainstream than yours. I think JWST will show that there are many bright galaxies at 9>z>7, and that they will almost all be relatively small, and close together. I do think that most of them will show metallicity similar to ours, because I think that the brightest light comes from places where the early metal was created (just a prediction).

2008-Feb-15, 06:01 PM
I can't help but wonder why they think that the dark ages "began" when hydrogen became neutral, ... the universe was pervaded by a brightness approaching that of the Sun but from all directions during that epoch...

That is an amusing observation. I think that 'dark' in this sense didn't mean that it would look dark if you were there, but that there is little light (or visible information to us) being generated at those times. It is possible that the SKA will force them to use different terminology.

Ken G
2008-Feb-15, 06:18 PM
Normally, I think when one talks about the "dark ages", one means much later when the CMB really is dark, and there are also no sources of light as you say. When hydrogen is still ionized, it is a source of light, true enough, but it is also a sink for light-- and has no effect at all on the brightness you'd see if you were there except that it causes the radiation temperature to cool like the matter does, rather than at the faster rate of adiabatic expansion of light. So decoupling is when the CMB starts cooling somewhat faster than it was previously, and one might conceivably use that as the meaning of "dark ages", though I'd find that pretty stretched. If one instead uses the meaning of "dark" as "not counting any light that was already there", an only slightly less strange usage, then I can see what you are saying. Note this still does not rescue the horrendous reference to a "fog" of neutral hydrogen!