Most distant object ever seen… maybe

By Phil Plait | May 25, 2011 12:07 pm

Is this the most distant object ever seen?

[Click to deathfromtheskiesenate.]

That is GRB 090429B, a gamma-ray burst (or just GRB to those who want to sound nerdcool), the catastrophic and extremely violent detonation of a massive star. Think of it as a super-supernova, the death throes of a star that lived a short, hot, turbulent life. I wrote about them extensively in my book "Death from the Skies!", or you can get the details about how they form and why they’re so awesome in an earlier post.

Its distance is estimated to be a whopping 13.14 billion light years. If this holds up, it may be the single most distant object ever seen by humans.

But is this really a record-breaker? And why aren’t we sure? OK, this takes a wee bit o’ explaining, but I think you’ll like it. After all, it’s an explosion so big it’ll crush your mind into dust.

[UPDATE: Due to a typo in my math notes early on, I incorrectly said the distance to this burst was 13.4 billion light years. D’oh! I have corrected all the numbers below, and I apologize for the error.]

Boom! goes the dynamite

The important thing here is that they are so bright — emitting more light in a few seconds than the Sun will over its entire lifetime — that they can be seen for tremendous distances. In fact, they can be detected from clear across the Universe, which is where GRB 090429B comes in.

It was first seen on April 29, 2009 (hence the name 090429B — it was actually the second GRB seen that day) by Swift, NASA’s satellite specifically designed to detect GRBs and rapidly transmit their locations to telescopes on the ground. GRBs fade very quickly, in minutes or even seconds, so rapid response is critical. In this case, observations by ground-based telescopes quickly revealed this was an unusual burst. Within hours astronomers began to suspect it was vastly distant. Estimates started putting it at greater than 13 billion light years away, almost as far as an object can be in the distant Universe.

Far, far away

Frustratingly, clouds prevented the monster Gemini 8-meter telescope from getting a spectrum of the burst, which would have nailed down its distance. Without that, the distance can only be estimated. However, several factors indicate it really is at this extreme distance:

1) Using different filters, astronomers found that the burst was visible in the infrared, but not visible light. Why is this important? Because the Universe is expanding. OK, bear with me here; there are a few steps to this logic.

As light from very distant objects comes to us, it is working against that expansion. Light can’t slow down — it always travels at the speed of light (duh) — but it does lose energy. That shifts the color of the light into the redder part of the spectrum. At huge distances, far ultraviolet light gets shifted all the way into the visible part of the spectrum.

Here’s the fun part: as it happens, some gas in the Universe absorbs ultraviolet light on its way here, but lets visible light pass through. Now imagine a GRB really far away, so far that UV gets redshifted to the visible part of the spectrum, while the visible light from the GRB shifts into the infrared. Here on Earth, we’d see IR from the GRB (which started out life as visible light) but not anything in the visible (which started out as UV). That’s what we see with GRB 090429b; IR but no visible — that’s what that picture above from Gemini is showing. That strongly implies that the light from the burst is coming from a long way off. Examining just which colors of light got through versus what got blocked allows astronomers to estimate the amount of redshift and therefore the distance to the GRB (I describe this technique in more detail here).

2) The host galaxy is invisible, even to Hubble. Gamma-ray bursts like this one come from the explosions of massive stars, which don’t live long. They are born, live out their lives, and die violently in the span of a million or so years. These kinds of stars are formed in giant clouds of gas inside galaxies, and can be seen for quite some distance with powerful telescopes. After the GRB faded, Hubble was aimed at that spot of the sky and saw… nothing (as you can see — or can’t see, I suppose — in the inset image; click to embiggen). That again implies a huge distance to the galaxy, so far that even its mighty light is faded away to nothing.

3) Less convincingly, but still important, is that the burst had a relatively faint afterglow in X-rays. Had it been at a less extreme distance, it would’ve been brighter. This is by no means solid evidence of great distance (some bursts are just fainter in X-rays) but it’s consistent.

So we can’t absolutely confirm it’s at this vast distance, but it seems very likely (a calculation of the odds puts it at 99.3% certainty).

Broken record

And even if it truly is at this mind-numbing distance, it still may not be the record holder for most distant object: one galaxy has been observed that might be even farther away, but the thing is that hasn’t been confirmed yet either. So it’s a fair bet that GRB 090429b is the single most distant discrete object* ever seen.

In a funny coincidence, the light from this burst reached Earth less than a week after another burst which broke the previous record. GRB 090423 — seen on April 23 2009 –blew away the previous record for most distant burst, with a distance of 13.04 billion light years (technically, that’s not the distance now but tells us instead how long the light has been traveling) — technically speaking it had a redshift of 8.25. But it only held that record for six days. GRB 090429b has a redshift of 9.4, giving it a distance of 13.14 billion light years — 100 million light years farther away.

To give you some idea of how amazing this is, the host galaxy of the burst must be one of the first that formed after the Big Bang itself. It may have even still been in the process of initially forming when the burst lit off — the Universe had only been around for about 600 million years when the burst occurred. Think of it this way: the most distant thing we can possibly see would be 13.7 billion light years away, since that’s how old the universe is.

This burst is 96% of the way to that distance.

As our tech improves, and telescopes get bigger and more sensitive, we’ll no doubt find bursts farther away than this one. But not by very much! The farther back we go, the less room there is in the early Universe for such an event to occur. At some point we’ll reach that limit, and then these record-breaking events will come far less often. They’ll all be as far as they possibly can be from us.

But that’s no reason to be jaded. Each of these events is second only to the Big Bang as far as sheer violence and energy, and were so titanic they must have had a profound effect on the environment around them. I suspect that when we have a good catalog of the most distant bursts, we’ll find out just how much of an effect they had on the early Universe, so record-breaking or not, they’ll help us understand what happened when the Universe was very, very young.

As if GRBs weren’t cool enough.

Image credits: GRB: Credit: Gemini Observatory / AURA / Levan, Tanvir, Cucchiara; Swift image: NASA / Swift / Stefan Immler; artwork: NASA /Swift /Cruz deWilde; brightness sequence: Gemini Observatory/AURA/Penn State/UC Berkeley/University of Warwick, UK; Hubble: Levan / Tanvir / Cucchiara for NASA/Hubble

* I say "discrete" because the background glow of the Big Bang, called the Cosmic Microwave Background, has been observed, and that’s at a redshift of about 1000, at a distance of 13.7 billion light years. We literally cannot see any objects farther than this, because they didn’t exist yet! In case your mind hasn’t already been blown by this post.

Related posts:

New burst vaporizes cosmic distance record
Swift bags most distant titanic explosion ever seen
Naked eye visible GRB
Titanic GRB still going strong
Record-breaking galaxy found at the edge of the Universe!


Comments (66)


    You wrote a book?


  2. Mircea

    How far in time from the Big Bang?

  3. Aside from this being amazingly awesome, I simply love the fact that we can’t even see anything in that location with hubble. Just one of those grand mysteries showing you how even more amazing the universe truly is.

  4. Diego

    Could we actually see the Big Bang with a Big enough telescope?

  5. Kappy

    @Mircea about 300 Million Light Years from the Big Bang, meaning that it occurred 300 Million Years after the creation of the universe. This means that in 300 Million Years an early galaxy had to begin forming and a suppermassive star had to get burning and go supernova.

    @Diego we already “see” the Big Bang. In theory everything that IS exists as a result of the Big Bang. Also we can see the cosmic background radiation that is left behind as a result from the Big Bang. Essentially the Universe still hasn’t fully cooled from it’s creation, so even in empty space a small amount of residual radiation exists.

  6. Scott B

    “The host galaxy is invisible, even to Hubble.”

    Is there any reason to think there’s a galaxy to be seen? I’m not up to date on the latest galaxy formation theories, but wouldn’t massive stars have formed before galaxies (at least as we know them) did? If this did occur 13.4 billion years ago, that’s only around 300 million years since the Big Bang. Are we sure galaxies had formed before this?

  7. Eddie Janssen

    A couple of months ago you wrote about the Hubble constant. It was determined to be 73.8 plus or minus 2.4 km/sec/megaparsecs. (
    Some people who responded (respondents 7 and 16) suggested that the speed of light divided bij the Hubble constant would result in the radius of the visible universe.
    When we take the lower limit of the Hubble constant (71.4) you arrive after c/h and converted into lightyears at 13,697 billion lightyears. That is the same as 13,7 billion you mention in the text.
    My question: Does c/h(0) result in the radius of the visible universe?
    I can understand the reasoning and its logic, but that does not necessarily make it true.

  8. Jim Johnson

    So… since this thing exploded…
    … before us
    … before the first life that eventually gave rise to us
    … before interstellar dust & gas coalesced to form a star with a planet on which this life could live
    … before much of that dust & gas was first created in the supernova deaths of earlier generation stars
    … possibly before those earlier generation stars even formed from coalescing interstellar gas clouds themselves.

    That’s a long time.

  9. Diego

    @Kappy, i know that. What we see is the result of It. Could we see the event itself?

  10. Philip Clarke

    Is it 13.4 or 13.14? Only the bbc and say 13.14.
    Such an amazing thought, something so close to the beginning of the universe.

  11. Kappy

    @Diego: I’m not sure there is anything to “see”. The instant the expansion began there was obviously a huge release of energy which we already do see, the cosmic background radiation. Then during the inflationary period, there wouldn’t have been any events that would cause huge spikes in detectable radiation because the matter hadn’t coalesced into anything of significant mass for fusion to take place, the universe was essentially “dark” during that period.

  12. Eddie Janssen

    I may have mixed up , and . at 1:10…

  13. Chris A.

    We can’t see the Big Bang per se, for two reasons:
    1) It didn’t happen in some place in a previously-existing, large, empty universe. Space itself has been expanding since the Big Bang, and the Big Bang happened everywhere in that space simultaneously.
    2) We can only see back in time to the epoch when the universe was transparent. Before that, light only traveled a short distance before being absorbed and re-emitted, thus providing a pervasive fog preventing us from directly seeing what came before.

    So, when we look at the cosmic microwave background (in all directions), we are seeing as close to the Big Bang (in time) as is possible (with electromagnetic energy, anyway). Now, if we could only make our gravitational wave detectors a lot more sensitive, we might “see” back closer to the Big Bang with gravity waves. But a better analogy would be that we would be “hearing” the Big Bang in that circumstance.

  14. Robert S-R

    I think Diego means, if we look far enough, can we see the Big Bang, er, “banging,” as it were. I think the short answer is no, because (correct me folks, if I’m wrong) we’re inside of it. So every direction we look in we see this faint fuzzy stuff, and it’s ALL Big Bang.

  15. Timmy

    I think I see what Diego is getting at.
    The Big Bang happened 13.7 billion years ago. So if we could travel 13.7 light years out and had a powerful enough telescope, we could see it happening.
    Johnny Goodboy Tyler did something similar so he could witness the destruction of the Psychlo home planet.
    Unfortunately not even Wesley Crusher’s space magic can travel that fast. Maybe a time travel episode?

  16. Doodler

    Any chance this was one of the long hypothesized Population III stars going off?

  17. Dax

    (Someone needs to call the janitor to clean all this grey matter off my desk.) XD

    That was probably the best post I have read on this site in a while.

    BTW, still working through your book, but loving every page.

  18. Chris Winter

    Population III stars, I am fascinated to learn, are thought to be the earliest stars. A new hypothesis has them spinning very fast, and thereby able to enhance the “s-process” that creates heavy elements like strontium.

    So the primordial stars were not so poor in life-supporting elements as I supposed.

  19. Siosilvar

    From the article: “As light from very distant objects comes to us, it is working against that expansion. Light can’t slow down — it always travels at the speed of light (duh) — but it does lose energy. That shifts the color of the light into the redder part of the spectrum. At huge distances, far ultraviolet light gets shifted all the way into the visible part of the spectrum. ”

    Really? I always thought the redshift came from things moving away from us, so the light’s frequency is effectively lower than when it was emitted. The loss of energy here comes from the inverse square law – intensity of light is inversely proportional to the square of the distance.

  20. Thorne

    I need some help with the distances and times, here. My only astronomy course was 35 years ago, and was pretty basic, and even then this concept messed with me, so any help will be appreciated.

    This GRB went off 13.4 billion years ago, because it’s now 13.4bly away? How is this possible? Even if the mass of matter which eventually coalesced to form our galaxy were traveling in a direct line from the center of the Big Bang, we couldn’t possibly be that far from that center, since we can’t be moving at even an appreciable fraction of the speed of light. The same would be true for the GRB, I presume.

    So, if the GRB detonation occurred at 0.3 billion years AB, and were on the opposite side of the center of the Big Bang, then the furthest the light on THIS side of the center could have traveled would be 13.1bly. If it’s only reaching us now, that would put us about 0.6bly from the “edge” of the universe, or the furthest distance light could have traveled from the Big Bang. My rusty arithmetic tells me that we would have to have been traveling in this direction at a speed of roughly 95% of the speed of light in order to achieve this. I know that can’t be right!

    By my reckoning, if we had traveled only 6.85bly from the center (a generous distance, as that would still require moving at 0.5c) then something 13.1bly distant (and therefore 13.1 billion years old) would have to be at least 6.25bly from the center, which would mean that it would have to have been much older than 0.3 billion years.

    I’m quite sure my logic is flawed here somewhere, but I’m damned if I can figure out where. Can anyone help me out, or point me in the right direction? I’m not even sure I’ve made my point clear, here.

  21. Justin Togail

    @Thorne: Perhaps because the Big Bang happened everywhere? There was no “center” of the explosion.

  22. Javier

    How come the energy traveled so many years and still does not reach “the end of the Universe”? As I get it, the event took place that many years ago, and by that time the Universe should have been “smaller”. At what rate does the spot we ocupy on the Universe is receding from the spot where this GRB took place? Which is faster: Universe expansion or the speed of the energy across it?

  23. T-storm

    I thought I heard something that day.

  24. Chief

    From what I’ve tried to figure out, the big bang resulted in an rapid expansion of the “proto” universe many times faster than that of light. Once the expansion gave the universe enough physical space, elementary particles and thus the laws governing them became “locked in”. Thus if I understand it. the universe was quite large and then settled down to the “growth” we have today and light then takes time to cover the longer distance eventually catching up to us to be observed.


  25. David

    The light is redshifted because of the Doppler Effect not because its doing work against gravity and losing energy; that would be gravitational redshift. More specifically it’s the Relativistic Doppler Effect.

  26. Dean

    Wait, the CMB at 13.7Bly is redshift 1000 but this GRB at 13.14Bly is only redshift 9.4?? That’s a heck of a log scale kicking in there, lol.



    The loss of energy here comes from the inverse square law – intensity of light is inversely proportional to the square of the distance.

    The inverse-square law applies to the collective energy of all of the individual photons per square metre at a given distance. What Dr. Phil Plait meant, when he said that light can’t slow down but it does lose energy, was that each individual photon’s frequency is reduced from a high energy state to a low energy state, in order for the photon to maintain the speed of light as space is stretched by the expansion of the Universe.

  28. Bill

    Hate to break it to you, but we have not, nor ever will see the “most distant object in the universe”. We are merely seeing an image of a moment in time 13.14 billion years ago that has finally reached our puny little senses. That is the limitation of science, isn’t it. We haven’t really seen anything.

  29. Messier Tidy Upper

    Just a brief speck of radiation at wavelengths our eyes can’t even physically see.
    So remote, so distant, so hard to comprehend in meaning.
    And yet what a wonder and what a blast beyond our ken
    When we realise what it means through clever minds!
    (Somehow the words of King Ozymandias “Look on my works ye mighty and despair” seem appropriate.)

    Was this the explosive hypernova ending of a Population III star that was the very first (or one of the very first) stars that ever formed – and one of the largest and most luminous ever?

    Did this GRB result in a massive black hole, one of the first ever formed and perhjaps the core of as Galactic supermassive black hole? Or was the star totally blown to shreds of stardust and creating the first ever heavier elements like gold, uranium and carbon?

    Coming from a time the cosmos was literally freshly born (well give or take a few million or hundred million years) this “news” has got to be among the oldest ever heard (or discerned in X rays and infra-red) but so astounding and thought-provoking and incomprehensibly impressive. Love it. Great write-up, BA thanks. :-)

  30. Messier Tidy Upper

    @16. Doodler : “Any chance this was one of the long hypothesized Population III stars going off?”

    I think it’s hard to see how this could be anything *except* a population III star being that distant and thus that early in the comos although I could, of course, be mistaken. 😉

    Not sure exactly when the first population II stars were born.

    I wonder too what the spectral class of those earliest generation of stars was – Type O seems insufficent and inadequate for describing such elephantine 300 or more solar mass behemoths (the most massive stars known in today’s universe have only about 100 to maybe , really pushing at the upper limits, 120 solar mass as I understand it) and weirdly enough too, I guess the lack of metals usually means classification as metal poor “sub-dwarf” stars!

    Seems to me the stellar leviathans that were the Population III stars deserve a spectral class of their own – class X or even Z perhaps? It’ll be interesting to see if we can ever get a spectrum of one of them.

  31. Don Q

    My way of “understanding” things like how something can be so far away that it must have traveled at the speed of light, starting at the big bang, to get there is this:

    Way back then, when these things/places were created, the rules (laws of physics) were different. I don’t just mean some of the constants were different, I mean the *big* different! To say the bang happened here or there, and things moved in this or that direction, or at this or that speed appear to have no meaning whatsoever. In effect, there wasn’t any “there” there. Things (?) were free to do what seems to violate our sense of “reality” (reality is really such a limited place).

    Another “proof”… Black holes are so massive that even light can’t get out, and certainly any mere physical object or activity, explosion or whatever going on inside the event horizon can’t get out. And if massive/super-massive black holes are even more so, imagine the effect of having all the mass in the entire universe at the ‘point’ of the beginning of the Universe. Certainly nothing could get out of this super-super-super-massive black hole, not even the big bang.

    But here we are.

    In that place… time? distance? inverse square? *What*? That place never even heard of such things. Trying to impose our measuring tapes and stop-watches on that place is folly.

    That’s what makes me go Wow!

  32. Jeffersonian

    I understand that space itself expanded (that there wasn’t a big empty universe for the big bang to occur inside of), and I understand that this GRB happened 13.1 billion years ago (that we are looking back in time). Still, doesn’t that mean that we are seeing toward the “center”, i.e. the relative site of the initiator locus? Isn’t this 96% of the way there and therefore in the neighborhood of what was once the entire neighborhood?

  33. Karl-Heinz

    Like Jeffersonian(35), I don’t REALLY understand this max distance issue. Maybe because the 4 dimensional space-time universe is so difficult to understand. Here are MY questions:

    1. If the light took 13.14 billion years to get here, this GRB-object (whatever is left of it) had 13.14 billion years time to travel even further – and as I understand it is travelling pretty fast – how far away is it now?
    2. If this GRB-object was born about 600 million years after the bigbang – it could have been only max 600 million light-years away from us – or say the place that was going to become us. How come the light travelled 13.14 billion years? Are we expanding THAT fast?

    Anyway, Phil, thanks for your great blog and your very nice book – a great and fun way to understand the wonders of the universe – and the many other issues you tackle.

  34. Someone

    So this is pretty much a picture from a very, very young stadium of the universe, huh? That is pretty impressive.

  35. Bob

    @21 Thorne

    I think you may be missing the concept that the distance comes from space expanding, causing the apparent motion between galaxies.

    So the light left this GRB when everything was MUCH closer together, but during the intervening eons, the distance between everything grew. I know-this idea was/is a tough one for me to conceptualize.

    One analogy I like to use is an ant on a rubber band (or balloon). Say an ant starts walking on a 2-inch rubber band at 2 inches per hour. You would expect him to reach the other end in 2 hours. Then you stretch the rubber band to 4 inches. The ant is still walking at 2 inches per hour, but now it’ll take him 4 hours to reach the other end. His speed hasn’t changed, but the distance increased, so it takes longer.

    The Balloon Analogy:
    Put a bunch of dots (stars/galaxies) on a balloon (space) inflated to a 4 inch diameter. Now inflate the balloon to 8 inches. The distance between the dots has increased- the galaxies/planets/stars move away from each other (or the space between them increases) creating apparent motion between them.

    Hope that helps (any comments on this from the smart folks around here would be appreciated!)

  36. Chris W


    The Big Bang didn’t have a center. There isn’t one specific point in spacetime we can look at today and say, “that’s where the Big Bang happened” as the Big Bang wasn’t an explosion that took place at a point in pre-existing spacetime. Rather, every point in space was, 13.7 billion years ago, part of the Big Bang, and space has been expanding ever since, carrying us all along with it. The Big Bang happened in my kitchen – and yours!

    Neither does the universe have an edge – although we can quibble about that depending on what we mean by “edge” when talking about the observable universe, as there are events sufficiently distant that their light will never reach us.

    As for us traveling at an appreciable velocity of the speed of light – yes, we are, relative to distant objects, just as high redshift objects are traveling at an appreciable velocity of the speed of light relative to us. This is of course due to the expansion of space. And objects at sufficient distance have recession velocities >c, which may seem impossible in special relativity, but since this is due to the expansion of space itself we’re in the regime of general relativity and all bets are off.

    Also, the 13.4 billion year figure is the light travel time from this GRB. The distance to the GRB is significantly greater, because space has been expanding as those photons crawled across the universe. Off the top of my head I’d guess the remnant of that GRB is “now” something like 70 billion light years away. Depending upon how one defines “now,” of course – it’s important for everyone to agree on a choice of coordinates.

    (Hope this helps. Sorry to be brief, but I’m sure there are some much better online descriptions of Big Bang cosmology and how best to picture it than I could scribble here, and some were probably written by our gracious host.)

  37. BillZBub

    I would love to see an interactive graphic of some sort that shows the most distant objects we’ve observed in each direction from the milky way. In other words, imagine you have a camera at the center of the milky way and you can pan it around freely. Dots would be visible in all directions that are colored based on their distance. That would give us a great sense of where we fit in the universe. I’ve always wondered if we even know which way the center of the universe is.

  38. Shantanu

    Great post. Just one correction. Light doesn’t strictly travel at the speed of light in the universe.
    It gets Shapiro delayed due to gravitational potential of interevening matter along line of sight.
    The Shapiro delay due to grav. potential of our galaxy is about 3 months (See

  39. Tom (H. Type)


    I’ve always had a problem with the “Balloon analogy”. If space is expanding at the speed of light then something 13.4 Billion light years away (i.e. the other side of the balloon) would be expanding in the other direction with space getting bigger in between at the speed of light. So we would never see it as the light beam would never reach us.
    I believe that expanding space/time is not smooth (like the surface of a balloon) but bulgy. With large bulges were space/time is expanding faster in those areas were matter (dark or light) densities are lower and deep recesses were matter densities are higher.
    So we get to see some very distant objects by looking down those slower expanding valleys.

  40. ghoppe

    @Tom (H.Type)

    Space isn’t expanding at the speed of light. The speed of expansion of space depends on the distance of an object. The further apart two objects are, the faster the expansion of space. This makes sense if you think about the balloon analogy.

    Hubble recently nailed down the expansion rate of the universe to an uncertainty of 3.3% to be 73.8 km/s per MPc. For every additional million parsecs a galaxy is from Earth, the galaxy appears to be traveling 73.8 kilometers per second faster away from us.

    My back of the envelope calculations show that the speed this event appears to be travelling away from us is, therefore, a significant fraction of c: 0.9917

    Another fun fact, if my calculations are correct, this means the space between the Earth and Sun is expanding at the rate of 11.3 meters per year!


  41. EJN

    Saying the object is 13.14 billion light years away is somewhat misleading, that is really
    the lookback time. The actual distance, called the co-moving distance, depends on
    knowing the proper cosmological model. Using the currently accepted lambda CDM
    with a FLRW (Friedmann-Lemaitre-Robertson-Walker) metric and with Z= 9.4
    & H_0 = 70, the co-moving distance is about 30 billion light years.

  42. kingthorin

    Why are we just hearing about this now?

    What made GRB 090423 so different? We heard about it right away ( and, etc), why did the one on the 29th take 2 years longer to hit the news?

  43. kingthorin

    @EJN isn’t it kind of irrelevant to talk about things being so far away? Maybe at this point in time it really is 30billion light years away. But isn’t it more likely that the object doesn’t even exist at this moment in time. It’s nice that something blew up over there 13.14billion years ago and now due to universe expansion etc would be ~30billion LY away…but chances are now it’s empty space, a blackhole, something completely different than what we’re observing.

    Wouldn’t it be more accurate to describe these things as “oldest object ever observed” or something like that?

  44. Thorne

    @37 Bob

    Thank you for the analogies. I do understand at least the concept of expansion of space, but still the timing of it escapes me. Light still moves at the same speed, and the expansion of space is, I presume, somewhat below that speed. As I understand it, the limits of the observable universe are those points where the apparent speed of expansion equals the speed of light.

    Using the expanding balloon analogy is misleading, I think. I rather see the surface of the balloon as the “edge” of space/time, the shell of light which was emitted by the Big Bang, and which is expanding outward at the speed of light. Our galaxy is a mote of dust inside of that shell, moving (mostly) outward, away from the center, but at a much slower speed. And there my mind just boggles. I still run into the problem of light from near the beginning of the universe just managing to catch up with us now, when in fact it should be much closer to the expanding outer shell.

  45. Tom (H. Type)


    Thanks, that makes a little more sense now…wow, my universe just expanded, although not at the speed of light :)

  46. The best explanations of these things that I know of are on Ned Wright’s site. I recommend reading through the whole thing and looking at his spacetime diagrams:

  47. Darren

    @49 Thorne
    “As I understand it, the limits of the observable universe are those points where the apparent speed of expansion equals the speed of light.”

    Not necessarily. Imagine that the balloon was foggy until it reached a particular size, then the fog cleared. From the time of clearing, a ring is expanding around you that shows the extent of the visible balloon. The edges of this ring are not expanding faster than light, but you cannot see farther.

    As time goes by the ring will be larger and will be encountering portions of the balloon that *are* receding faster than light relatively. Only at that point does the starting age becomes irrelevant and the expansion becomes the limiting factor.

    “Using the expanding balloon analogy is misleading, I think. I rather see the surface of the balloon as the “edge” of space/time, the shell of light which was emitted by the Big Bang, and which is expanding outward at the speed of light.”

    No, that’s not the right way to use the analogy. Think of the balloon as only being occupied by flatlanders. The balloon appears locally flat, and they cannot perceive the “up/down” dimension. The “center” of the balloon is not a concept to them. Instead all the dots used to be closer, and now they are farther. There is not spot on the surface that was the center. Scale everything up a dimension to us. There is no location in our 3D space that was the center.

  48. Doodler

    For those pondering the expansion of spacetime with respect to the location of this here event, let this bake your grey noodles….

    If the explosion occurred 13.14 billion years ago, shouldn’t the star have been significantly CLOSER to us when it actually exploded?

    13.14 billion years ago, the universe was a pretty small place compared to today (albeit still pretty huge after half a billion years of ballooning).

    Just my layman’s way of thinking, if we’re seeing that explosion at 13.14 billion light years away today, it should (remember, kids, layman’s thinking) have been right there when it originally popped off in the first place. So it was already 13.14 billion light years away, correct?

    I’m pretty sure someone with more experience with Expansion theory could torpedo that thought, but I’d welcome it if it made the whole picture somewhat less fuzzy.

  49. CB

    @ Doodler

    If the explosion occurred 13.14 billion years ago, shouldn’t the star have been significantly CLOSER to us when it actually exploded?

    13.14 billion years ago, the universe was a pretty small place compared to today (albeit still pretty huge after half a billion years of ballooning).

    Just my layman’s way of thinking, if we’re seeing that explosion at 13.14 billion light years away today, it should (remember, kids, layman’s thinking) have been right there when it originally popped off in the first place. So it was already 13.14 billion light years away, correct?

    I believe you’re correct that the star would have been significantly closer to our point in space when the explosion occurred. But as the photons from this event traveled, the universe continued expanding. So the original distance between us would be much less than what the photon ended up traveling, which is much less than the “current” distance to the point in space where this explosion occured oh-so long ago.

  50. Jeffersonian


    We can’t really talk about where “we” were when this happened because our region of space is only 4.6 billion years old.

    Great clarification.
    But even though there’s no 3D locus of initiation, wouldn’t there still be a more condensed, general neighborhood, relative to our position today, and wouldn’t we be looking in that space-time direction ?
    (i.e., reverse-engineer and picture the balloon deflating)

  51. Adam

    “with a distance of 13.04 billion light years (technically, that’s not the distance now but tells us instead how long the light has been traveling)”
    You have got to do a post on this! This page blows my mind:
    It seems that light can have an effective speed of many times the speed of light. Put another way, the universe is only 13.7B years old, but has a radius of 47B light years. What gives??

  52. Richi

    You do not mention the hardness ratio of the Xray faint afterglow. Without that and with the lack of spectroscopy it is very difficult to asses the distance only from a spectral energy distribution of 4 points (z,J,H and K) and an upper limit in visible (HST non detection). It might well be a GRB in a heavily obscured but nearer host galaxy. Any UV data from UVOT, or achival from GALEX?
    BTW: You do not need a massive galaxy to have an extremely massive star. If such a huge cloud exists it must be seen in radio, must’t it?

  53. un malpaso

    @57 Adam:
    Remember, the reason space itself is dark (i.e. why we don’t see light everywhere around us) is that very reason: because the universe is so big (and has expanded so fast) that light hasn’t been fast enough to catch up.
    The universe is actually stretching the light as it (space) expands, but there is more to the universe than we ever can see, since space itself has outpaced the distance light can travel in the age of the universe.
    And light doesn’t have any other “effective speed” than its own speed (c), only because its speed at any time is being measured (by us, in this case) in relation to the space around it anyway.

    Right? (looks around to see if anyone here with more experience/knowledge on the subject disagrees… if I am not clear on something, enlighten me.. ha!)

  54. Ricky

    “13.14 billion light years”

    what is that in dog years?

  55. What’s .26 Billion light years between friends?

  56. robert

    what if…we were or could instantly be in the area of where the farthest object visible is…what would we see? nothing or everything? and what about the edge of the universe? dosent this imply that there is a center? and from that center how far would we be from it…einstien predicted that the universe would someday collapse back in on itself but so far not enough material has been detected to account for such an event and the farther out we can see the faster the universe seems to be traveling…just like an explosion…it does make you wonder and thats the awsome beauty of it

  57. Jerry

    Let me try to phrase the question in simpler terms.
    Assuming the universe started with a big bang and has been expanding ever since, that would mean that in order for us to have arrived at a location to view an event which happened 13 billion years ago we would have to have travelled faster than the speed of light in order to arrive at the viewing position before the light from the event did. And that’s impossible (or is it?).


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