New burst vaporizes cosmic distance record

By Phil Plait | April 28, 2009 7:00 am

The light had been traveling a long time, oh, such a long time. It had passed gas clouds, tenuous patches of dust, interstellar and then even intergalactic space. It had blasted through countless atoms and unimaginable stretches of space and time, and now the light had been reduced to a mere echo of its once epic luminosity. But it was enough… after spending the age of the Universe careening through it, those few remaining photons finally saw something blocking their path that they couldn’t barrel their way through.

NASA’s Swift satellite.

And finally, after billions of years, in the early hours of Thursday, April 23, these electromagnetic bullets slammed into Swift’s gamma-ray detectors. And when they did, they signaled the detection of the most distant discrete object in the Universe ever seen.

Gemini telescope detection of GRB 090423A.

Gamma-ray burst GRB090423A, as it’s now called, not only breaks but completely destroys the previous record holder. In astronomical parlance, it has a redshift of 8.2, meaning the light from this burst has been traveling for more than 13 billion years! The previous most distant GRB was seen only just last September, but this new one is nearly 200 million light years farther away.

Wow. Not too long ago, the most distant objects we had seen and been able to measure were quasars, galaxies spewing out huge amounts of radiation. The record holders were at (what seems now to be measly) redshifts of 5 or 6, corresponding to 12 billion light years away or so. But then gamma-ray bursts came on the scene, and blew away those distances.

Swift is a satellite designed to detect these distant blockbusters, and has recorded the fading light from over 30 GRBs so far this year, and several hundred since its launch in 2004. I worked on the education and public outreach for Swift for several years, and I remember very well when we bagged a redshift 7 burst, blowing away the previous record. It was around then that I started to suspect that we might actually see much farther ones, even out to a redshift of 10 (nearly 13.2 billion light years). This detection of GRB 090423A indicates that’s no pipe dream.

Dana Berry artwork of a GRB
Artwork of a GRB at the moment of truth.

A gamma-ray burst happens when a massive star — maybe as much as 100 times the mass of the Sun — explodes in a supernova. We’re not exactly sure why, even now, but the forces in the heart of this beast can focus the energy of the explosion into two beams of cosmic destruction; vast death rays blasting out from the core. The energies are beyond belief, dwarfing even the Sun’s total emitted energy over its entire lifetime. Any planet in that beam’s way within a few thousand light years of the burst is in for some serious hurt (which I lovingly detail in my book).

But I doubt that happened for 090423A. When it went off, the Universe itself was only 630 million years old! There probably weren’t enough heavy elements to make earth-like planets, though I suppose gas giants might have been around by then… but even the first stars themselves were hardly more than 200 million years old at that time. It’s hard to imagine what the Universe must have looked like when it was so young.

Finding such ancient gamma-ray bursts is crucial in understanding what the early cosmos was like. We can find out what proportion of elements existed in stars back then, and the way the light is absorbed by intervening dust and gas tells us about them as well. We know precious little from this era of the Universe, because any object in it was sp far away at the time that they are essentially invisible. Only the titanic brightness of a GRB allows us to see them at all.

The star that exploded to form this GRB was probably not among the very first in the Universe to be born; even 230 million years is a long time compared to the lifetime of those extremely massive stars, which may have exploded after living only a million years or so. But it may have been born in the second generation, stars that formed from gas blown out by the explosions of those first stars. If so, we’re one step closer to seeing what the very first objects in the Universe were, and how they behaved. That’s a mystery that has been on the minds of many astronomers for many years, and Swift is whispering to us that we’re almost to the point where they are within our grasp.


Image credits: Gemini Observatory/NSF/AURA, D. Fox and A. Cucchiara (Penn State Univ.) and E. Berger (Harvard Univ.); and Dana Berry, Skyworks Digital.

Comments (84)

  1. Stupid question: where were my atoms (the ones making up my body) when this event took place? How did I get so far away, so quickly, that light from the event took 13 billion years to reach me?

    Does this have something to do with inflation?

  2. Another, hopefully “not dumb”, question: How much of the universe is there that’s more than 13 billion light years away? Anything that happened more than 13 billion years ago, to something that is less than 13 billion light years away, would have already had its photons pass us.

    So, how much of the “original” universe is far enough from us to be possible to be seen?

  3. It’s a real skill getting children and gamma-ray bursters to sit still for a portrait.

  4. How much energy did that release?

  5. JackC

    I got a laugh out of the fact that all the Hayden displays indicating the age or size of the Universe – were on replaceable disks. So far though, it seems they are safe.

    And I am with Doubting Foo and Ken above. I have to go study this link a bit more I think:

    http://www.space.com/scienceastronomy/mystery_monday_040524.html

    JC

  6. Daffy

    Doubting Foo, that is something I have never understood either. It happened, obviously, but I don’t get the mechanics of it. Seems like my atoms had to have traveled faster than light. Maybe someone can help us grasp the concept…

  7. Lawrence

    The concept is somewhat difficult to explain, but it is a combination of the speed of light & the inflation of the Universe – the two actually resulting in a “faster than light” situation.

    That’s as best as I understand it, which is probably either wrong or mostly wrong.

  8. RL

    @Doubting Foo, Ken B., and Daffy,

    I recommend listening to some really good Astronomy Cast (Pamela Gay and Fraser Cain) podcast episodes. They covered your questions in recent “question show” episodes. Check them out.

  9. Pointybirds

    Doubting Foo/Daffy … my guess would be that the space itself between us and these events has been expanding, red shifting the light and slowing its arrival at our particular neck of the woods. I’m sure there are people far more knowledgable/anal here who can help out :)

  10. Nigel Depledge

    Wow!

    And I thought it was a long way down the street to the chemist’s!

  11. Jack Mitcham

    I’m kind of surprised they’re still gamma rays after such a long cosmological redshift.

    And Doubting Foo:

    I might be 100% wrong about this, because I haven’t taken special relativity in school yet. The way I understand it is that we are kind of being “carried away” from that light by the expansion of the universe. The distance between us and the source of the GRB is expanding. The light, which is stuck moving at c, is just barely overcoming this expansion at first. As the space between ourselves and the GRB decreases, there is less space between us to expand, so it continues to get closer and closer.

    Even though the GRB is traveling at c, the relative velocity compared to Earth is far less than c, especially at first. It’s like running up the down escalator in a way.

    What this means is there is a “horizon” as to how far back we can see. At some point, the universe will be adding more space faster than a photon traveling at c can traverse that space. That far out, events happening are forever outside of our light cone. We can never know about what’s outside of our horizon.

    Please correct me if I’m wrong on any of this, which I probably am.

  12. Gavin Polhemus

    Space has been stretching since the big bang, and continues to stretch today. You are not moving very quickly, and the distant galaxies are not moving very quickly. Still, because space is stretching, the distance between you and the distant galaxies is growing. The redshift tells us how much the universe has grown since the event occurred. This gamma ray burst is at a redshift of 8.2, which means that space has stretched by a factor of 9.2 since the time of the burst (add 1 to the redshift to get the factor). Using the growth chart for the universe, we see that this means that the burst happened over 13 billion years ago.

    It is common to say that since the light has been traveling for 13 billion years, the it was 13 billion light years away. This is nonsense. Our galaxy was much less than 13 billion light years away from this burst when the burst happened, but the space has been stretching as the light traveled towards us, forcing the light to cover much more than the original distance. Since the space has continued to stretch, the current distance between us and whatever remains of this burst’s origin are much farther than 13 billion light years away. There is no nice way to convert times into distances when space is stretching by these huge amounts. It is best to just state what can be stated clearly: we are looking at an event that happened over 13 billion years ago.

  13. LIES! All of this is a LIE perpetrated by the God-hating atheist scientists! Everyone knows that the universe is only 6000 years old – the Reverend Billy Ray says so, from his counting of the Bible! Any of this “evidence” you claim to have is more LIES created by the Devil to confuse us and lead us away from God’s Word-

    Sorry, I can’t go on with a straight face. But this is utterly fascinating, looking so far back. The universe must have been a very strange place 13 billion years ago.

  14. According to current theories we should never discover light that has been traveling for over 14 billion years, or even let’s give ourselves a bumper, say 15 billion years. This would be a prediction that so far has been held to be true, since we haven’t discovered anything that has traveled that long. So far so good, science predicts and experimentation supports it.

    But . . . what if we do? Suppose we do discover a GBR that has been red-shifted so far that it is older than the age of the Universe? What would happen? The whole edifice of scientific thought would come crashing down, right? Of course not! But it certainly would be shaken around a bit.

    You see this is how I see science working. We learn, we hypothesis, we test, we experiment, and we keep on going! As we learn more, we change the theories, making them better and better, more inclusive and better explanations. This is how the process works! we never stop learning! So if we did discover a GBR older than our current thinking predicts, we will keep on working on it until we understand it better! We will formulate new ideas, have new theories to test, and keep on going!

    This is why science is fun! This is why it drives people so hard! And this is also why when some Creationistic claims that ‘science is so locked into one viewpoint they will never admit to something contradicting it’ is so wrong! This is the moment scientists live for! The point where the testing and experimenting reach the limit of human knowledge and understanding and they truly live for expanding those limits. This is science!

    tedhohio@gmail.com

  15. Daffy

    Sincere thanks to everyone for trying to explain this. I admit it makes my brain hurt…but I think I am grasping the concept!

  16. IVAN3MAN

    Phil, in the penultimate paragraph, fourth line, typo: it should be so, not “sp”. :-)

  17. Torbjörn Larsson, OM

    Those things really burst onto the scene!

    How much of the universe is there that’s more than 13 billion light years away?

    Wikipedia claims under the heading “Observable universe” that the “edge of the observable universe is now located about 46.5 billion light-years away.”

    But as for the universe itself, it is likely unbounded in every direction on account that it is flat in the standard cosmology (besides the occasional bump from a mass). A flat universe would naturally go unboundedly in every direction.

    As for actual measurements I believe that studying the microwave background radiation modes and cosmic variance (i.e inherent uncertainty from studing the universe over the whole observable distance) sets a lower limit of some 5-10 observable radii, but I may be wrong.

    Seems like my atoms had to have traveled faster than light.

    No, that is impossible by way of relativity. But there is AFAIU nothing in relativity that prevents space-time itself from expanding faster. It certainly did during inflation.

    The way I think of this is like raising a raisin bread. As the bread raises the individual raisins don’t move much compared to the dough. Choose one raisin as reference (Milky Way). Raisins close to it will not move fast but further away the raisins will move away fast in relation to the Milky Way raisin.

    [So also, from such an analogy, while the edge of the observable universe is expanding a light year per year, AFAIU distant objects will move away faster and "disappear" over the edge. The future universe will look more and more empty, as distant galaxies are for ever racing away from each other.]

  18. Gavin Polhemus:

    This is how I had the concept explained to me many years ago…

    Imagine that you have a rubber band that is 1 foot long. There is an ant at one end. The ant then starts walking at a constant speed towards the other end, while at the same time, the rubber band starts stretching.

    At any point in time, all parts of the rubber band are getting further away from each other, and the further apart the points, the faster they are going relative to each other.

    At some time in the future, the ant finally reaches the other end. Despite it starting only 1 foot away, it has now traveled several feet to get to the other end, which is now even further away than the ant has traveled.

    So, for example, despite the “event” occurring when the points are only 1 foot apart, you have to travel 3 feet to get to the other side, at which time, the points are now 5 feet apart.

    Perfectly clear now. :-)

  19. Torbjörn Larsson:

    How much of the universe is there that’s more than 13 billion light years away?

    Wikipedia claims under the heading “Observable universe” that the “edge of the observable universe is now located about 46.5 billion light-years away.”

    (I sure hope that quoting is correct. We need a “preview” feature.)

    I guess in a forum such as this, I need to be a bit more precise in my wording on something like this? :-)

    “How much of the universe is there that is far enough away such that light which was emitted more than 13 billion years ago has yet to reach us?”

  20. Thanks for all the answers. I will have to chew on this some more. My brain feels about the way it felt when I went from procedural programming languages to object oriented programming languages back in the 1990′s. I think my internal concept of certain things has to change for me to feel like I really get all this.

  21. phunk

    There’s no way to know at the moment how much universe there is outside out observable part.

  22. phunk

    that should have been “our observable part”

  23. csrster

    It should be possible to calculate backwards and work out how far away the GRB was from the-place-where-the-Earth-would-later-be-formed at the time the GRB occurred. I’m not sure that it would be especially meaningful, but it might help to make the discussion more concrete.

  24. smerk

    @where were my atoms (the ones making up my body) when this event took place?

    Sorry if i missed other replies to this already, but your atoms per se didn’t exist yet
    when this event took place ~13 Gyr ago. The current standard model framework for
    particles and the cosmos seem to indicate that the primordial hydrogen/helium with
    a dash of Li, had to be fused to heavier elements by first and second generation stars.
    These in turn had to burp or even explode to release their “ash” back into the cosmos
    to gravitationally collapse all over again into new solar systems like ours. Only then
    were there the heavier elements, e.g. Si, Fe, … that make up the bulk of our home
    and the C, N, O, P, … that make up life here.

  25. George F

    Maybe we should ask former Apollo 14 astronaut Edgar D. Mitchell. He seems to have info that we know very little of.

    http://www.washingtontimes.com/news/2009/apr/21/astronaut-says-were-not-alone/

  26. Torbjörn Larsson, OM

    A flat universe

    Btw, the other day I learned why the universe is flat from reading Stenger’s “God – the failed hypothesis”. It’s a lot of interesting modern physics related in simple form there, among other things that one can now show that the universe has exactly zero energy. (Which was news to me.) So should be flat, in the simplest models.

    [Actually it is interesting details of physics too in the 2002 paper "ON THE TOTAL ENERGY OF OPEN FRIEDMANN-ROBERTSON-WALKER UNIVERSES" by Faraoni and Cooperstock.

    Technically, AFAIU one can't universally describe localization of energy in general relativity (GR) due to such stuff as the nonlinearities in the situation (from space-time affecting mass-energy and vice versa). So there are many energy principles that can apply, or not, at various times.

    But by looking at gravity's action as a dynamical system one can resolve the situation here. Roughly, FRW cosmologies (as AFAIU standard cosmology gives) has flat space, zero energy, as an attractor state. This includes so called de Sitter (dS) spaces which AFAIK aren't flat. Conversely they can transform the problem so that dS spaces are attractors for points arbitrarily close to flat space, so dS spaces and its relatives are zero energy too.

    As far as I understand it, GR considered by itself as Schwarzschild space-time has inherently an effective boundary - there is a sphere enclosing all matter at any time by way of how the physics are set up - so there will always appear to be too much mass compared to the actual space-time. But FRW cosmologies are in reality unbounded, and by passing to them one can study the actual dilution of energy density to zero.

    And as they point out, that vanishing total energy, with potential emergence from another system without energy exchange with a third system, means that the universe is also a thermodynamically closed system. Again news to me that one could decide either way. And somehow that feels like a satisfying resolution too.]

  27. Avanti Shrikumar

    The universe is expanding, certainly. Pointybirds is right; expansion -of- space, not expansion -into- space. When the burst actually took place, the source couldn’t have been more than 630 million light years away, because the universe itself was not more than 630 million years old (it would have had to recede faster than the speed of light in order to get any further, in which case I think it would be totally unobservable…though not impossible since this recession is due to expansion of space).

    “Anything that happened more than 13 billion years ago, to something that is less than 13 billion light years away, would have already had its photons pass us”

    Incidentally something that is currently 13 bil light years away was a lot closer 13 bil years ago, due to the expansion of the universe. Just another complication to consider. The edge of the observable universe is 46.5 billion light years away, even though the universe itself is not more than around 13.6 billion years.

    That’s another thing…13.6bil is given by 1/H, but isn’t that only an upper-bound on the age of the universe, since the expansion rate was faster at the beginning, implying a younger universe? So maybe this was indeed among the first generation of stars? I’m out of my depth here.

  28. Torbjörn Larsson, OM

    Ken B:

    I guess in a forum such as this, I need to be a bit more precise in my wording on something like this?

    Actually I suspected that this was the actual question. But you would have gotten the same answer FWIW, since I believe I can’t easily find or, worse, actually calculate the answer. Call me Hubbled by the circumstances. ;-)

  29. Avanti Shrikumar

    Oh wait, I didn’t consider inflation. I really am not sure about these things; I have an amateur’s understanding, really.

  30. Jason

    I’m looking at the time frame involved here. Universe was very young when this thing went boom, according to Phil, only 630 million years old. I realize very massive stars go psychotic far quicker than smaller ones, however with the time it would take a star to form in the first place it’s hard to imagine it to be that shrot of a lifespan. Unless I’m somehow missing something, being the null-science minded, which is pretty likely.

  31. I think Phil should straighten this out once and for all … As correctly pointed out above, although the event happened 13 billion years ago, it is INCORRECT to say that the GRB was seen 13 billion light years away. It is a common misconception that size of the universe must be equal to the cosmological time multiplied by the speed of light. That would be true only in a flat universe. On cosmological scale, our universe is highly curved. Due to expansion of the space metric the light from this GRB traveled close to 46.5 billion light years and was actually heading away from us during the initial part of its journey (according to ΛCDM)

  32. Attempting to understand this cosmology makes me feel like an ant trying to climb Mount Everest. But, possibly like ant, I don’t care how big the mountain is, I am going to try to climb it anyway.

    I wonder about the plausibility of matter in the universe that is beyond our visible horizon being massive enough to account for what we call dark energy. Put another way, could dark energy just be the gravity of ordinary matter in the universe beyond our time horizon?

  33. so will all these gamma rays turn everyone into Incredible Hulks?

    and if everyone are Incredible Hulks, would they then not be so incredible?

  34. Bjoern

    @Jack Mitcham
    “I’m kind of surprised they’re still gamma rays after such a long cosmological redshift. ”

    Well, the redshift is “only” 8.2, hence the original frequency of the radiation has changed by a factor of 9.2 only. If you take high-energy gamma radiation and divide its frequency by 9.2, you still have high-energy gamma radiation usually…

    @Ted Herrlich
    “Suppose we do discover a GBR that has been red-shifted so far that it is older than the age of the Universe?”

    It doesn’t work this way. Red shift is related to age in such a way that for a red shift of infinity, you’ll get the age of the universe. Hence no red shift can ever be measured which would give an age larger than the age of the universe.

    OTOH, there are lots of other ways in which we could discover that things are older than the (assumed) age of the universe…

  35. The light had been traveling a long time, oh, such a long time. It had passed gas clouds, tenuous patches of dust, interstellar and then even intergalactic space.

    ALT: A long time ago, in a galaxy far, far away….

    Jason Says:
    I realize very massive stars go psychotic far quicker than smaller ones,

    Sounds like another discussion thread….
    ;)

    J/P=?

  36. American Voyager

    So now I’m a bit confused. Did the gamma rays Swift picked up travel 13 billion light years or not? I think I understand it using the walking up a “down” escelator analogy but I want to make sure. If they did, could we calculate what the absolute magnitude of the blast would have been? Would it have been brighter than our sun? It must have been staggering.

  37. Andy

    Hopefully someone sees this buried under all the other great comments, but I have a question:

    How do we know how far away this GRB is/was? What did we use to measure distance?

    -Andy

  38. @American Voyager, the gamma rays burst happened 13 billion years ago but traveled an effective distance of almost 46.5 billion light years

    To be observable from such a distance it must have outshined anything that we know of in the universe. Our sun has absolute (visual) magnitude of 4.83 which means you could barely see it with naked eye from the distance of 10pc ~= 32.6ly (def not if you were in a bigger city)

  39. Bend

    @PsyberDave

    You’ve been reading New Scientist! :) It would sure be nice if that was an explanation for Dark Energy, as it means with enough data we could really good a good picture of whats outside our observable universe! Its an exotic idea as any ive heard!

  40. Layman

    Special relativity is hard to understand for the layman. When an object moves close to the speed of light, time for that object slows down; at the speed of light time stops altogether. So what does Phil mean when he says that the photons have been traveling for a long time? For them the trip has taken no time at all! How do they become an echo of their original luminosity in no time at all? Perhaps because they are more and more spread out. But does a single photon become reduced in luminosity?

    And I thought special relativity was supposed to correct Newton’s idea of absolute space and time. Yet we say that the light detected is 13 billion years old in a universe 14 billion years old. Sounds like there’s some absolute clock ticking away somewhere to make these statements!

  41. @TheChef you had me goin’ for a second there

  42. Troublemaker

    How confident are we in the redshift measurement? High redshifts have been claimed before, only to be debunked or forgotten. I’m not intimately familiar with the systematic errors associated with photometric redshift determinations for GRBs, but it seems premature to do too many somersaults over a possible continuum break.

  43. BeckyWS

    @ Scibuff (after just asking you a question on the same topic at Universe Today!)

    If as you say the magnitude must have been larger than anything we know of, then how can we be sure that it was a massive star (as is being suggested)? Or are people assuming that stars then were very different and much higher energy when exploding? As a related question, although GRBs come from different theorized sources, do we have any good examples of the objects that caused them, as we do for supernovae, like where a star disappears? And is there a common magnitude to them or do they seem to be variable and therefore attributable to different sources? Sorry for all these questions, and thanks for your time.

    Becky

  44. Mchl

    Phil… the way you started this entry made me feel as if I was in Total Perspective Vortex from D.Adams’ novel…

  45. If the photons from this GRB crashed into the detectors on SWIFT, does that mean that they travelled 13.2 billion light years at the speed of light without hitting anything else?

    If they hit a planet or an asteroid or even a dense dust cloud, then they would have never made it to SWIFT and we would never know about it. Right?

    And while I understand that the vastness of the universe is mostly empty space, isn’t it kind of amazing that the light from this GRB made it all the way to SWIFT without hitting something else first?

  46. chutz

    And while I understand that the vastness of the universe is mostly empty space, isn’t it kind of amazing that the light from this GRB made it all the way to SWIFT without hitting something else first?

    Yes it is amazing and unlikely, but don’t forget that the Universe is a _big_ place. It’s so big that even extremely unlikely events like gamma rays traveling 13.2 billion light years without hitting anything happen pretty regularly. Gamma ray bursts themselves are a pretty uncommon event, and having one that is pointed directly at Earth so we can see them is even more uncommon, yet SWIFT is detecting hundreds a year. This is because the Universe is so vast that uncommon events happen quite regularly.

  47. Pieter Kok

    Phil, thanks for not saying that the GRB happened a few days ago! ;-)

  48. Selasphorus

    Wow. Absolutely wow.

  49. kappapavonis

    @scibuff says

    “….. It is a common misconception that size of the universe must be equal to the cosmological time multiplied by the speed of light. That would be true only in a flat universe. On cosmological scale, our universe is highly curved. …..”

    Not quite – that misconception would be true in a “static” universe, i.e. a universe without expansion or contraction – this was Einstein’s view when he developed General Relativity.

    On a cosmological scale, our Universe is not highly curved – the part that we can measure is flat (or very close to it), meaning that the internal angles of a triangle add up to 180° no matter how large the triangle. The best line of evidence pointing to our Universe’s flatness is the spectrum of the cosmic microwave background. (http://map.gsfc.nasa.gov/)

  50. I’ve been exploring the possibility of a linkage between gamma ray bursts happening in the Milky Way galaxy and a GHZ (Galactic Habitable Zone). For example, if we assume that gamma ray bursts (GRB) only occur in stars with a mass of greater than 100 solar masses and the rate of star formation in the Milky Way is 10 stars per year, then on average there will be one GRB in galaxy every 9,700 years. Over the course of geologic history (4.5 billion years) there have been 460,000 GRBs. But if we further restrict the angular width of the emission cone to 5 degrees (on both ends) then only 350 of these GRBs will be visible from the earth (or 0.075 percent of them).

    Peforming a random simulation (Monte Carlo program) the brightest GRB visible from the earth occurred at time = 1.77 billion years (2.73 billion years ago). It was only 1,165 light-years away from Earth and had an energy flux of 70 million joules per square meter (or the amount of energy flux received by the sun in 14 hours). Since GRBs typically last ~10 seconds this power flux is ~5,000 times the power flux of the sun.

    I also computed the distance breakdown of all 350 visible GRBs. Only 13 of them occur within a distance of 10,000 light-years. Also, I compute the total sum of all the energy fluxes form all the visible GRBs – it comes out to 190 million joules per square meter. That’s a lot of energy falling on the earth’s surface over the course of the earth’s history.

    *********************************************************************

    Program to compute gamma ray bursts in the Milky Way galaxy

    Rate of star formation in Milky Way galaxy = 10.00 stars/year
    Minimum mass of a star that can produce a GRB = 100.00 solar masses
    Maximum time for the simulation = 4.500E9 years
    Full beam width of the gamma ray burst = 5.00 degrees
    Cylindrical radius of target from center = 26,000.0 light-years
    Cylindrical z-position of target = 50.0 light-years

    Number of gamma ray bursts in galaxy per year = 1.031E-4
    Average time between gamma ray bursts = 9.699E3 years
    Number of gamma ray bursts during simulation = 4.640E5
    Gain of the gamma ray beam = 2,101.33

    Number of gamma ray bursts visible from target = 350

    The 10 brightest gamma ray bursts:
    Time …….. Distance …. Energy flux
    (years) ….. (l.y.) …… (joules/m^2)
    ——- ….. ——– …. ————

    1.773E9 ….. 1.165E3 ….. 7.001E7
    1.122E9 ….. 1.801E3 ….. 2.722E7
    2.983E9 ….. 2.693E3 ….. 1.439E7
    4.199E9 ….. 2.963E3 ….. 1.204E7
    1.173E9 ….. 2.952E3 ….. 1.019E7
    2.703E9 ….. 3.570E3 ….. 7.273E6
    1.251E9 ….. 5.751E3 ….. 3.524E6
    2.147E9 ….. 6.594E3 ….. 2.746E6
    1.817E9 ….. 7.653E3 ….. 1.743E6
    3.010E8 ….. 7.689E3 ….. 1.667E6

    Minimum …. Maximum …….. Number of
    distance … distance ……. visible
    (l.y.) ….. (l.y.) ……… GRBs
    ——– … ——– ……. ———
    0 ………. 1,000 ………. 0
    1,000 …… 2,000 ………. 2
    2,000 …… 3,000 ………. 3
    3,000 …… 5,000 ………. 1
    5,000 …… 7,500 ………. 2
    7,500 …… 10,000 ……… 5
    10,000 ….. 20,000 ……… 32
    20,000 ….. 30,000 ……… 71
    30,000 ….. 50,000 ……… 125
    50,000 ….. 75,000 ……… 86
    75,000 ….. 100,000 …….. 23

    Sum of the energy flux from all the gamma ray bursts =
    1.942E8 joules/m^2

  51. How does changing the angular diameter of the beam affect the parameters for GRBs? In general, the narrower the beam the fewer the GRBs that are visible from the earth and the greater the distance to the nearest GRB. For example, for a beam width of 1 degree only 11 GRBs would be visible over the course of the earth’s 4.5 billion year history and the nearest one would be 18,000 light-years away. For a beam width of 30 degrees more than 12,000 GRBs would be visible over the earth’s lifespan and the nearest one would be only ~500 light-years away. Thus, a narrow beam diameter reduces the threat of GRBs to Earth life.

    *********************************************************************

    Gamma Ray Burst Parameters versus Beam Width
    (at the earth)

    Rate of star formation in Milky Way galaxy = 10.00 stars/year
    Minimum mass of a star that can produce a GRB = 100.00 solar masses
    Maximum time for the simulation = 4.500E9 years
    Cylindrical radius of target from center = 26,000.0 light-years
    Cylindrical z-position of target = 50.0 light-years
    Number of gamma ray bursts in galaxy per year = 1.031E-4
    Average time between gamma ray bursts = 9.699E3 years
    Number of gamma ray bursts during simulation = 464,000

    Beam …… # Visible . Distance of
    Width ….. GRBs …… nearest GRB
    (deg) …………….. (light-years)
    —– ….. ——— . ————–

    1 …….. 11 …….. 1.799E4
    2 …….. 49 …….. 2.132E3
    5 ……. 350 …….. 1.165E3
    10 …. 1,262 …….. 1.140E3
    20 …. 5,437 …….. 7.797E2
    30 … 12,185 …….. 5.417E2

  52. Next, let’s consider the effects of where the target planet is located in the Milky Way galaxy. I ran the program for various target planets located in the middle of the galactic disk at various radii from the galactic center. Surprisingly the results do not show a strong correlation between distance from the galactic center and number of visible gamma ray bursts. The number of visible GRBs is in the range 306 to 361, an 18 percent difference. Thus, it wouldn’t matter where the earth was located in the galaxy. It would have been affected by approximately the same number of GRBs over its 4.5 billion year history.

    In terms of the brightest GRB visible the range is from 2.556E6 to 7.001E7 joules per square meter, a factor of 27 difference, but most of this difference is caused by statistical fluctuations in the mass of the GRB, since the maximum value of 7.001E7 occurs at a distance of 26,000 light-years and not the center of the galaxy where we would expect it. Likewise, the distance to the nearest GRB goes from 1,165 to 5,865 light-years. There does appear to be a modest correlation between location and this value with all of the values greater than 3,000 light-years occurring at locations farther than 30,000 light-years from the center of the galaxy, and all the values less than 3,000 light-years occurring at locations nearer than 30,000 light-years from the center.

    Thus, planets in the outer part of the galaxy may experience the same number of GRBs as planets in the inner part of the galaxy over some fixed period of time, but the GRBs will tend to be farther away for planets in the outer part of the galaxy relative to planets in the inner part of the galaxy.

    Thus, in terms of establishing a GHZ (Galactic Habitable Zone) there may be an effect in terms of distance to the nearest GRB with the outer part of the galaxy (greater than 30,000 light-years from the center) having greater distances and thus, less gamma ray flux. For the inner part of the galaxy statistical fluctuations swamp out any such effect. There is no narrow band for the GHZ as there is for the circumstellar habitable zone.

    Of course, these calculations do not take into account the central supermassive blackhole. During times when it is actively feeding the central galactic bulge (inner 6,000 light-years) of the galaxy may become a very lethal place for life.

    *********************************************************************

    Gamma Ray Burst Parameters versus Location

    Rate of star formation in Milky Way galaxy = 10.00 stars/year
    Minimum mass of a star that can produce a GRB = 100.00 solar masses
    Maximum time for the simulation = 4.500E9 years
    Full beam width of the gamma ray burst = 5.00 degrees

    Distance . # Visible .. Energy flux …. Distance of
    from ….. GRBs ……. of brightest … nearest GRB
    galactic ………….. GRB ………… (l.y)
    center ……………. (joules/m^2)
    (l.y.)
    ——– . ——— .. ———— … ———–

    0 …….. 321 …….. 2.591E7 …….. 1.799E3
    5,000 …. 360 …….. 5.569E7 …….. 1.431E3
    10,000 … 325 …….. 1.875E7 …….. 2.356E3
    15,000 … 361 …….. 2.635E7 …….. 1.782E3
    20,000 … 355 …….. 1.561E7 …….. 2.373E3
    26,000** . 350 …….. 7.001E7 …….. 1.165E3
    30,000 … 311 …….. 5.259E6 …….. 4.366E3
    35,000 … 346 …….. 3.425E6 …….. 5.323E3
    40,000 … 321 …….. 2.556E6 …….. 5.865E3
    45,000 … 306 …….. 9.425E6 …….. 3.116E3
    50,000 … 311 …….. 5.244E6 …….. 4.038E3

    ** — location of the earth

  53. EJ

    scibuff, can you show us the math on the 46.5 billion ly number?

  54. Using a similar Monte Carlo calculation but setting the minimum mass of the star to 10 solar masses we can compute the distance to the nearest supernova event. One such calculation is as follows. Supernova occur in our galaxy roughly once every 140 years. The nearest once was ~40 light-years away and happened 1.5 billion years ago. Assuming a Type Ia supernova it would have had a peak apparent magnitude of -18.7 (270 times brighter than the full moon).

    I don’t know if there were any organisms alive at the time with eyes, but if there were and they happened to look up they would have been greeted with an astonishing sight – a star hundreds of times brighter than the full moon lasting a month or so.

    Incidentally, ~40 light-years is also the distance to the nearest black hole which this nearest supernova generated. It should be out there somewhere if only we knew where and how to look. I wonder if it would be detectable via gravitational lensing.

    **************************************************************************

    Program to compute gamma ray bursts in the Milky Way galaxy

    Rate of star formation in Milky Way galaxy = 10.00 stars/year
    Minimum mass of a star that can produce a GRB = 10.00 solar masses
    Maximum time for the simulation = 4.500E9 years
    Cylindrical radius of target from center = 26,000.0 light-years
    Cylindrical z-position of target = 50.0 light-years

    Number of supernovae in galaxy per year = 7.032E-3
    Average time between supernovae = 1.422E2 years
    Number of supernovae during simulation = 3.165E7

    Minimum distance of any supernova = 4.342E1 light-years
    Occurring at time = 2.987E9 years
    Peak apparent magnitude (Type Ia supernova) = -18.68

  55. Paul

    I thought they had found gamma ray bursts to be a result of merging black holes and a neutron star or 2 neutron stars merging?

    http://www.universetoday.com/2005/10/05/gamma-ray-burst-mystery-solved/

    http://www.nasa.gov/mission_pages/swift/bursts/short_burst_oct5.html

  56. Spencer Attridge

    Mr Larsson, good Hubble pun!

    I thought a good metaphor for the expanding universe/inflation, was the expanding balloon….

    Imagine a tiny ballon that (for the sake of the metaphor will never break) has two dots on it (representing either atoms/lightwhatever)…on expansion of the ballon the distance between dots increases (faster than c).

    I like this image as I find it easy to imagine

  57. @EJ “scibuff, can you show us the math on the 46.5 billion ly number?”

    I don’t think you can compute a precise number unless you assume a particular cosmological model. For example, consider a photon travelling at the speed of light (c) over some infinitesimal time step (t):

    Then we have two components to its velocity:

    ds = c * dt is the distance it travels over the time step due to the innate velocity of light

    dr is the extra distance it travels due to the expansion of space:

    dr = H * r * dt

    where H is the Hubble constant (actually not a constant over time), and r is the hyperspace radius of the universe

    So you can put these two together via the Pythagorean theorem and you get:

    dl = sqrt(ds^2 + dr^2) = dt * sqrt(c^2 + H^2 * r^2)

    If you integrate dl over time you will get the final path length of the photon that you need. The only trouble is that this is a difficult integration. You need to know how both H and r vary over time which depends on a model.

    Let’s assume we let H be a constant over time (70 km/sec per Megaparsec) which most cosmological models don’t accept. Then you can come up with a formula for r:

    r = r0 * exp(H*t)

    where r0 is the initial hyperspatial radius of the universe at the beginning time. Then plugging into the dl equation you get:

    dl = dt * sqrt(c^2 + H^2 * r0^2 * exp(2*H*t))

    This is still a nasty integration. I don’t believe it has an analytical solution but I could be wrong. It depends on r0, a measurement in hyperspace, which we probably don’t know too well.

  58. Paul M.

    “…those few remaining photons finally saw something blocking their path that they couldn’t barrel their way through.”

    But some would have just missed Swift and kept on going – maybe somebody else will catch those one day.

    Wow

    Wow for the GRB… and us for finding it!

    - and by us I mean humans… not that I was involved in any way

  59. peteshmm

    I understand we are not obliged to believe this interpretation of this burst! It is just
    the best analysis the observers can give at the moment.

  60. Don’t laugh. Is it possible that one night the sky will have a blinding flash of light from the big bang?

  61. ethanol

    Molly:

    I believe that the blinding flash of the big bang is now the cosmic background microwave radiation. There’s been an awful lot of expansion and redshift since that happened…

  62. Okay, maybe I’m missing something here.

    Phil said that a gamma ray burst is created when a very massive star explodes as a SUPERNOVA.

    I thought that if the star were massive enough to form a black hole — which a 100-solar-mass star would certainly be — there would be NO supernova explosion. The star would swallow itself, and only the twin Death Rays of the Gamma-Ray Burst would escape; and that such an event was called a HYPERNOVA.

    So, what’s the skinny here, anyway?

  63. fred moore

    If space has been uniformly expanding at the rate posited,

    then after the 4.6 billion years since the Earth formed,

    we all should just be able to see the first rays from our own Sun …

    oh, about ….

    NOW!!!

    And what was the reason given for the Pioneer spacecraft speeding up as it entered interstellar space?

    Ya gotta love this stuff!

  64. If my brain did not turn to mush trying to imagine this awesome event, Tom Marking’s calculations caused it to implode and disintegrate into a mass of twisted and tangled neurons all sending the same message: “Does not compute…”

    Thanks Tom! :) :) ;)

  65. TMB

    But the real question is: does it have a Gunn-Peterson trough?

    [TMB]

  66. csrster

    “So what does Phil mean when he says that the photons have been traveling for a long time? For them the trip has taken no time at all!”

    I think it’s pretty obvious what he means. He means that there are two events (the GRB explosion and the photon detection) and the time separation between them _measured in the Hubble frame_ is 13 billion years.

    Tom:
    “dl = sqrt(ds^2 + dr^2) = dt * sqrt(c^2 + H^2 * r^2)”
    Why do you add these two components in quadrature?

  67. Pieter Kok

    csrster: because he is calculating distances (in space and time), so you have to use Pythagoras (the relativistic version).

    Also, when you talk about duration or length in relativity, you always have to state with respect to which observer. For observers co-moving with the light from the GRB there was no time at all between emission and detection, but for us there was 13 billion years (it’s a bit more complicated, because you also have to take into account the non-negligible speed of the source of the GRB, and the gravitational redshift).

  68. Torbjörn Larsson, OM

    The best line of evidence pointing to our Universe’s flatness is the spectrum of the cosmic microwave background.

    Yes, I wouldn’t call a spatial curvature of 0.010 + 0.014/-0.012 highly curved… “These are consistent with a cosmological constant, w = − 1, and no spatial curvature Ωk = 0.”

    - Wikipedia, on extended modeling of the standard cosmology.

    “With WMAP alone the curvature is weakly constrained, with marginalized limits Omega-k = −0.099 +0.085 −0.100, and Omega-Lambda < 0.76 (95% CL), assuming a Hubble prior of 20 < H0 0. Without this prior on the positivity of Omega-Lambda, limits on the curvature are weakened.” [Symbols replaced.]

    - WMAP 5-year results.

    I thought the standard cosmology, the un-extended model, actually has w = − 1 and Ωk = 0 built in. (I further believed that Minkowski space, local lorentzian space-time, also has Ωk = 0. Perhaps I’m mistaken on both counts though.)

    @ Spencer Attridge:

    Thanks! I feel inspired by higher stars [read: "Bad Astronomy"].

  69. Torbjörn Larsson, OM

    does a single photon become reduced in luminosity?

    No, but the radiation field would. A photon is an instantiated quantum of the EM field.

    I’m not sure it is meaningful to speak of an elementary particles existence outside of the field.

    [In the classical naive Copenhagen interpretation of QM that would be, if I'm not mistaken, that it is meaningless to speak of observable properties of wave functions outside of the observation of them. If you tried, you would have particles with "wave properties" and wave functions with "particle character", as they used to say.]

    because he is calculating distances

    Nitpick: I believe he is (correctly) summing path-lengths.

    “A distance is but a path well traveled.”

    [Einsteinian version: "A distance is a travel worth waiting for."]

  70. @csrster ““dl = sqrt(ds^2 + dr^2) = dt * sqrt(c^2 + H^2 * r^2)”
    Why do you add these two components in quadrature?”

    The ultimate answer is that we treat the expansion of the universe to be occurring in another dimension orthogonal to the usual 3 dimensions. If the expansion was taking place in the usual 3 dimensions then there really would be a center to the expansion. So orthogonality allows the use of the Pythagorean theorem. The calculation of total path length of a photon is similar to the path length of a spiral in planar geometry although there are some complications because we don’t think the “pitch” of the spiral in the case of cosmology is constant. It is this changing “pitch” of the spiral which must be obtained from some specific cosmological model.

  71. Once again, Phil is ahead of the curve.

    http://apod.nasa.gov/apod/ap090429.html

    How many times does an image appear on APOD a few days after Phil tells us about it? :-)

  72. Michael L:

    If my brain did not turn to mush trying to imagine this awesome event, Tom Marking’s calculations caused it to implode and disintegrate into a mass of twisted and tangled neurons all sending the same message: “Does not compute…”

    ITYM:

    Does not comp*&^%jhvkjY.'/=TE$hf
    NO CARRIER

  73. @Tom @csrster For redshifts greater than 0.8, the relationship between redshift and distance is more complex, as account has to be made of many other factors. This is the distance formula

    You can experiment with different values of universe curvature using this online calculator

  74. @tracer “Phil said that a gamma ray burst is created when a very massive star explodes as a SUPERNOVA. I thought that if the star were massive enough to form a black hole — which a 100-solar-mass star would certainly be — there would be NO supernova explosion. The star would swallow itself, and only the twin Death Rays of the Gamma-Ray Burst would escape; and that such an event was called a HYPERNOVA. So, what’s the skinny here, anyway?”

    A lot of this is not known with any degree of certainty. The limit of 100 solar masses for a black hole producing supernova is too high by about a factor of 10. The current limit is thought to be 10 solar masses or thereabouts. Thus, if a star has more than 10 solar masses it will form a black hole during a supernova event. But there are great uncertainties here starting with the Tolman-Oppenheimer-Volkoff limit:

    http://en.wikipedia.org/wiki/Tolman-Oppenheimer-Volkoff_limit

    Which tells you how massive the supernova remnant has to be in order for a black hole to form. It’s currently thought to be 1.5 to 3.0 solar masses so that’s a factor of 2 uncertainty right there. That would mean a 10 solar mass star undergoing a supernova would have to lose 70 to 85 percent of its mass during the supernova, but we don’t know this percentage to any high degree of precision.

    So what is a hypernova? It’s thought to be a supernova involving an extremely massive star with 100 to 150 solar masses. A hypernova would generate a black hole which would probably be more massive than the garden variety 10 solar mass generated black hole. As to the other details of the explosion, besides the gamma rays being focused into a tight beam on both ends, not much is known. The assumption that the gamma ray beams are the only radiation is probably unfounded. We don’t know at the moment because we have never witnessed a hypernova up close and personal although there is some speculation that Eta Carinae is just the sort of star that could cause a hypernova.

    Also, something like two thirds of all planetary nebula have a dumbbell shape indicating that even these less powerful explosions are not isotropic in direction but focus their energy along an axis. So there may not be such a peculiarity concerning GRBs and their tightly focused beams after all.

  75. DrFlimmer

    @ Tom Marking:

    Is your life so boring or how long did you need to make all these calculations?
    Nontheless, they are very interesting, thanks a lot!

    Btw: I hate it that I cannot register on Universe Today for some reasons (I don’t receive the confirmation mail and I tried two different addresses).

  76. IVAN3MAN

    @ DrFlimmer,

    I was wondering why you had not been making any comments there. I registered on day #1 and I had no problem.

  77. EJ

    @Tom Marking – thanks a lot, that was a good explanation. I’d assumed 46.5 billion ly was predicated on assuming some specific cosmological model, but I couldn’t figure out which one.

  78. @scibuff “For redshifts greater than 0.8, the relationship between redshift and distance is more complex, as account has to be made of many other factors. This is the distance formula”

    Oooo, that’s a very nasty integration. The reciprocal of a square root of a cube plus a square. I guess that’s what computers are for. Thanks for the calculator.

    Playing around with some of the numbers in the calculator I get:

    H0 = 71
    Omega-M = 0.27
    Omega-Vac = 0.73
    Z = 8.2
    Current age of universe = 13.666 Gyr
    Initial age of universe when photon started = 0.63 Gyr
    light travel time = 13.035 Gyr
    Comoving radial distance = 30.017 Gly
    Comoving volume within redshift Z = 3265.010 cubic Gpc
    Luminosity distance = 276.142 Gly

    The path length of the photon is 13.035 billion light-years in this case. Changing the parameters I find it very hard to come up with a photon path length of more than ~30 billion light-years and if I do the age of the universe is longer than ~13 billion years. So it doesn’t seem that 46.5 billion light-years is a credible number. Maybe that is the comoving distance, not the path length of the photon.

  79. DrFlimmer

    I was wondering why you had not been making any comments there. I registered on day #1 and I had no problem.

    An honour being missed, too bad that it does not help. The next problem is that I cannot try again with the same nick and the same address, because it is already used (of course). Dammit.

  80. Ralph

    An analogy that may help get your mind around this. 2 dots and a marble on a rubber sheet. One dot is the observer, the other the location of the emission and the marble is the light emitted. As the marble rolls toward the observer, the rubber sheet is stretched slightly slower than the marble rolls. Eventually, the marble gets to the observer dot, but it has rolled much more than the distance originally from the emission dot and the observer dot. The speed differential is how the red shift occurs and how we can measure the distance between the observer and emission point.

  81. headexplodes

    Seriously… just thinking about this is absolutely mind-boggling. And then I think of where the photons currently are that were traveling in the other direction. Will they run into something and finally end? Or will they speed along into infinity (and beyond!)? *head explodes again*

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