A gamma-ray burst detected in April by NASA’s Swift orbiter has a higher redshift (z = 8.26 ± 0.08) than any other celestial entity for which a redshift has been measured—except for the cosmic microwave background (CMB) at z ≈ 1100. That means the massive star whose collapse to a black hole the GRB is presumed to manifest was significantly more distant than any star or galaxy yet observed. Its demise provides a glimpse of the cosmos just 625 million years after the Big Bang. Beyond revealing that such stars already existed back then and providing a first approximation to their formation rate, the discovery adds a potentially powerful new probe to the search for the first generation of stars and the investigation of how UV radiation from early stars reionized the intergalactic medium. After the first moment of cosmic transparency, signaled by the CMB, and before there were stars, almost all the primordial hydrogen and helium was unionized. To reconstruct the history of cosmic reionization, one seeks to measure the absorption by neutral atomic hydrogen of light arriving from sources at various very high redshifts. Such observations with quasars have revealed that cosmic reionization was essentially complete by z = 6 (950 Myr after the Big Bang). But high-redshift GRBs seem to be essential for tracing its earlier stages. GRBs are briefly luminous enough to be seen at much greater distances than quasars. (N. R. Tanvir et al., http://arxiv.org/abs/0906.1577; R. Salvaterra et al., http://arxiv.org/abs/0906.1578.)—Bertram Schwarzschild
Earliest astrophysical object yet seen
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I apologize if this is a naive question but I was a biology major not physics.
So I understand that as we look at objects which are further and further away in space with telescopes like Hubble, we are actually looking at the light that left those objects further and further into the past.
If we are measuring the rate at which objects are moving away, it makes sense that the further out into space we are looking, the faster objects would be moving because we're looking back in time closer to the point at which the big bang occurred when things were moving super fast.
But how do we know what is going on 14 billion light years away from here right now if we can't see it?
Thanks for your consideration,
Phillip Schutzer
Rafi,
that is an excellent question and one of the subtleties that we Physicists and Astrophysicists unfortunately take for granted. The fact of the matter is that we can only look "back in time" and the farther we look, the farther back in time we see. If we wanted to see an event that is occurring right at this moment 14 billion light years away, we would have to wait 14 billion years from now to see it...
Regards!
Peter Amerl
I have perhaps a naive question as well.
This article appears to say that just 625 million years after the Big Bang the objects were farther apart than any star or galaxy yet observed. That probably means several billion years away.
I would like to understand, if there was indeed a massive Big Bang originating from a point, then only way the objects got this far apart in 625 million years after Big Bang from a starting point would be that they traveled at speeds much much faster than light. So, is it commonly understood that objects traveled much faster than speed of light (or speed of light itself) in early moments of creation?
Thanks in advance for clarifying this.
Amjad Soomro
Somehow this comment thread is following a different article than the one about which I originally commented.
The original article was relating the story about the measurement of the acceleration of the expansion of the universe by a researcher at Johns Hopkins (my alma mater).
My point was that we see acceleration increasing the further out into space we probe. But we are actually looking further into the past to a time closer to the big bang when things were naturally moving much faster.
I don't see how we can infer that the universe expansion is accelerating from this if we are actually only viewing the past. What is the evidence that the universe is expanding faster locally not billions of light years away from here and likewise not billions of years ago.
Thanks for your consideration,
Phillip Schutzer
Amjad: I wasn't writing about the spacing between objects at 625MYr after the BB being billions of LYrs. Rather it's the present distance between us and the GRB (or the "comoving" spot that marks its demise) that's greater than any implied by previous observations of stars or galaxies.
Rafi: One deduces the history of cosmic exoansion by comparing distance (as measured by apparent brightnesss) with redshift for supernovae over a wide range of redshifts.
Let's not get into the "red shift." Let's just talk about how anyone knows what is going on 14 billion light years away from here. Personally, I think Einstein was right as with all of his other good instincts, when he said that the universe was "static".
Notwithstanding the light wave-length artifacts of "looking back in time" at anciently faster moving objects, please prove that we have any way of knowing how fast things are moving away from each other 14 billion light years from Earth.
Thank you,
Rafi Schutzer
Supposedly, space CAN expand faster than the speed of light though nothing can travel through space FTL, that is the theory. It has been theorized that at higher energy level, as in the beginning of the universe that the speed of light was faster than now. My naive question is: Since the "measuring stick" is expanding as the universe expands, why would there be any redshift? The space itself is expanding so there is no change in the wave length since the units of measure are expanding as well. Why not more red = more intervening dust?