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Space Science

Gamma Ray Burst Visible At Record Distance 68

Invisible Pink Unicorn writes "A gamma ray burst detected on March 19 by NASA's Swift satellite has set a new record for the most distant object that could be seen with the naked eye. The burst had a measured redshift of 0.94, meaning the explosion took place 7.5 billion years ago. The optical afterglow from heated gas was 2.5 million times more luminous than the most luminous supernova ever recorded, making it the most intrinsically bright object ever observed by humans in the universe. The previous most distant object visible to the naked eye is the nearby galaxy M33, a relatively short 2.9 million light years from Earth."
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Gamma Ray Burst Visible At Record Distance

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  • by Naughty Bob ( 1004174 ) on Friday March 21, 2008 @11:52AM (#22820072)
    If I read correctly, a GRB of this magnitude occurring 2700 light years away would be as bright as the sun. Ouch.
  • Phew (Score:3, Interesting)

    by OrochimaruVoldemort ( 1248060 ) on Friday March 21, 2008 @11:57AM (#22820148) Journal
    so long as it isn't 100-900 light years away, the earth wouldn't be destroyed. still, it is going to be in the night sky for at least a few months
    • Re: (Score:2, Informative)

      by Anonymous Coward
      No. It's already faded from view. The peak brightness in the visual range, however, was estimated to reach about magnitude 5 or 6, which is about the same as the dimmest stars you can see from a really dark location.
  • Photoshop (Score:3, Funny)

    by esocid ( 946821 ) on Friday March 21, 2008 @12:01PM (#22820208) Journal
    I don't know...looks photoshopped to me.
  • Oblig... (Score:2, Insightful)

    Ze goggles!!! Zey do nothing!!!!!!!!!!

    (kisses karma goodbye)
  • by holmedog ( 1130941 ) on Friday March 21, 2008 @12:28PM (#22820648)
    Or perhaps it concentrated its energy in a narrow jet that was aimed directly at Earth. They're shooting at us!
    • by jandrese ( 485 )
      Alright, what did you guys do 7.5 million years ago to piss off some aliens halfway across the known universe? I'm looking at you holmedog.
      • 7.5 million years ago you say?
        But... according to the summary: "the explosion took place 7.5 billion years ago"

        And in order for our offensive behaviours to get to the aliens, we would have to give time for our message to get there. So really, what the hell did you people do to piss them off 15 billion years ago?!
        • Yeah, except 7.5 billion years ago, it was a lot closer (expanding universe, you know), so it's much less than 15 billion years ago. Well, maybe not *much* less, since the rate of expansion is accelerating... my brain hurts.
        • Re: (Score:2, Insightful)

          by Idiomatick ( 976696 )
          I think its safe to say whether 7.5M or 7.5B years it happened a long time ago in a galaxy far away...
      • The expanding wavefront of the earliest radio broadcast of a Wayne Newton record is much smaller than that. I think whatever is shooting at us is a lot closer.
  • by Lazarian ( 906722 ) on Friday March 21, 2008 @12:40PM (#22820806)
    Not to nitpick, but the article title should have been more along the lines of "Most distant naked-eye event recorded", since gamma rays themselves are not visible.

    Anyway, it's a good thing that this occurred so far away, instead of nearby. There are a few hypergiant stars known to exist in our galaxy like Eta Carinae and the Pistol Star which are inherently unstable. And in 2004 a GRB was emitted by a magnetar half way across the galaxy that, were it visible, would have been brighter than a full moon. Its been proposed that GRB's may be a factor in past extinction events here on earth.

    • Re: (Score:3, Informative)

      by Chris Burke ( 6130 )
      Not to nitpick, but the article title should have been more along the lines of "Most distant naked-eye event recorded", since gamma rays themselves are not visible.

      It's not the gamma rays they're talking about, but the afterglow caused by gas heated by the gamma rays, and this afterglow is partly in the visible spectrum, and was in fact visible with the naked eye (magnitude between 5 and 6, which is at the edge of unaided human vision). The title is completely correct.

      "No other known object or type of exp
      • "No other known object or type of explosion could be seen by the naked eye at such an immense distance," said Swift science team member Stephen Holland of Goddard. "If someone just happened to be looking at the right place at the right time, they saw the most distant object ever seen by human eyes without optical aid."

        There is no way of knowing what past humans eyes have seen. There may have been a more distant object at some time in our past that was viewed by human eyes, just not recorded.

        • There is no way of knowing what past humans eyes have seen.

          Thus the disclaimer of "No other known object".
    • Gamma ray bursts emit a *lot* of light at longer wavelengths than gammas. Actually, they spend more time emitting longer-wave light than they do emitting gammas. The gamma pulse is very brief, but the other forms of radiation last a lot longer.
  • by SleptThroughClass ( 1127287 ) on Friday March 21, 2008 @01:18PM (#22821374) Journal
    For you newcomers, a record was like a mechanical CD but larger. The diameter of a CD is about half that of a Long Playing Record, so "Record Distance" is a distance comparable to the width of two CDs. I don't know why astronomers are the ones studying lights at that distance.
  • From the article:

    > Later that evening, the Very Large Telescope in Chile and the Hobby-Eberly Telescope in Texas measured the burst's redshift at 0.94. A redshift is a measure of the distance to an object. A redshift of 0.94 translates into a distance of 7.5 billion light years, meaning the explosion took place 7.5 billion years ago, a time when the universe was less than half its current age and Earth had yet to form. This is more than halfway across the visible universe

    This contains some serious misund
    • Re: (Score:3, Informative)

      by ajs ( 35943 )
      The Universe is, in fact, at least 156 billion light years wide:

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

      • Well, different sources say different things, so I took the lower bound. (For example http://en.wikipedia.org/wiki/Observable_universe [wikipedia.org] states 78billion light years across for a lower bound based on WMAP data) And then I halved it for the radius, and rounded. The exact number doesn't matter for my explanation.
        • by techpawn ( 969834 ) on Friday March 21, 2008 @02:46PM (#22822348) Journal
          Just re-member that you're standing on a planet that's evolving and revolving at nine-hundred miles an hour.
          That's orbiting at nineteen miles a second, so it's reckoned, a Sun that is the source of all our power.
          The Sun and you and me and all the stars that we can see, are moving at a million miles a day, In an outer-spiral arm at forty-thousand miles an hour, of the Galaxy we call the Milky Way.

          Our galaxy itself contains a hundred-billion stars, it's a hundred thousand lightyears side to side.
          It bulges in the middle, sixteen-thousand lightyears thick, but out by us it's just three-thousand lightyears wide.
          We're thirty thousand lightyears from Galactic central point, we go round every two-hundred-million years.

          And our Galaxy is only one of millions of billion in this amazing and expanding Universe The Universe itself keeps on expanding and expanding in all of the directions it can whizz. As fast as it can go, the speed of light you know, twelve-million miles a minute and that's the fastest speed there is.
          So remember when you're feeling very small and insecure how amazing unlikely is your birth. And pray that there's intelligent life somewhere out in space, 'cos there's buger all down here on Earth!
          • At the risk of being spoil-sport:

            > As fast as it can go, the speed of light you know, twelve-million miles a minute and that's the fastest speed there is.

            That's actually quite wrong. We can see stars with a redshift of 6.3, meaning that it is moving away from us at 21 million miles a minute (compared to the 12 million miles a minute for the speed of light).
            • Technically (I know, I know) it's not moving away from us, but the intervening space is expanding at that rate. The fastest you can move through space is C, however, space itself is free to move (expand) at whatever rate it likes.
            • We can see stars with a redshift of 6.3, meaning that it is moving away from us at 21 million miles a minute

              If you assume that we are a stationary object and also assuming that space is flat. We know that both of those are incorrect. We are not stationary in space and space is not flat but a function of space-time. The earth may have a calculable velocity within our own space-time environment but the redshift of 6.3 which could attribute a perceived velocity of 21 million miles per minute is still less th

              • This whole nitpicking discussion sounds like it should be made into an episode of The Big Bang Theory. Considering some of the discussions Sheldon and Leonard have had over the most inane subjects, this would fit in nicely.
              • > If you assume that we are a stationary object and also assuming that space is flat.

                No, if you assume that we are a stationary object and that space is flat, then an object with a redshift of 6.3 would mean that it is moving away at 6.3 * speed of light = 70 million miles a minute. The 21 million miles a minute takes into account the curvature etc.
      • by nuzak ( 959558 )
        > The Universe is, in fact, at least 156 billion light years wide:

        But the universe is younger than that, so how ... oh man, my head was already hurting, I don't think I want to tackle this one.
        • by Eddi3 ( 1046882 )
          It's not actually that bad. It just means that the universe is expanding at about 5 light years in every direction from the center every year.

          Which would seem to mean it's expanding faster then light, the universal speed limit...

          Okay, *now* my head hurts.
          • The Universe isn't expanding from the "center", it's expanding everywhere. It is thus not limited to the speed of light.
            • by Eddi3 ( 1046882 )
              No, it *is* expanding from the center, however, this also means that everything is getting further away from everything else.

              I still don't see why that would allow it to violate the speed of light anyway (certainly not more then 2x).
              • There is no center of the universe, at least according to the cosmological principle. The balloon analogy is used a lot in this respect; when you blow up a balloon, its surface expands, but does not do so from a "center" -- every point on its surface moves away from all other points. Now, consider the three-dimensional universe as the two-dimensional space of the balloon surface, and you have an expanding universe without a "center" as we understand the concept (and you thought the idea of space expanding f
    • by ceoyoyo ( 59147 )
      It depends on how you define a light year. If you define it as the distance light WOULD travel in a year in a vacuum if space were not expanding or contracting, then you're absolutely correct.

      If you define a light year as the distance light travels in a vacuum in a year, then the article is consistent. I don't think astronomers really use light years as a measurement for cosmological distances for that very reason. But the general public thinks they know what a light year is, so press releases have to tr
      • Re:Article is wrong (Score:4, Informative)

        by JohnFluxx ( 413620 ) on Friday March 21, 2008 @03:07PM (#22822528)
        (Just for reference, I am doing an MSc in this field.)

        Your definition would be what cosmologists call 'comoving distance'. I have never seen a light year defined in this way however. The rate of expansion changes with time, so under your definition you would end up with things like that 2 * 1 light year != 2 light years, etc.

        It also means that a light year now, would be a different distance (in km) than a light year was a year ago, etc.
        • by ceoyoyo ( 59147 )
          You'd have a light year defined depending on the particular period of time you chose to use. It does have the advantage that light will have travelled a light year in a year. Or a billion light years in a billion years.

          Reading the (two) articles, the distance measure actually only appears in that one paragraph in the press release. Everywhere else they seem to just give the travel time. On the other hand, I plugged 0.94 into a redshift calculator and it spit out 2.38 Gpc, which would agree with the 7.5
          • See the reply I pasted from the author of the article - he explains it in detail better than I can. (Quick summary - the 'mistake' came during editing.
            • by ceoyoyo ( 59147 )
              A good explanation. Thanks for e-mailing and posting the result for us. I'm impressed you got such a quick reply on a holiday Friday.
    • Re: (Score:3, Informative)

      by JohnFluxx ( 413620 )

      I emailed the author, and they have now corrected the article.

      The article now just says:

      The explosion was so far away that it took its light 7,500,000,000 (7.5 billion) years to reach Earth! In fact, the explosion took place so long ago that Earth had not yet come into existence.

      And the title has also been changed to "A Stellar Explosion You Could See on Earth!" (Instead it was something about that it happened half way across the universe from us)

    • Re:Article is wrong (Score:5, Informative)

      by JohnFluxx ( 413620 ) on Friday March 21, 2008 @03:21PM (#22822696)
      For anyone interested, here's the email that I received from the author:

      Hi John,

      Thanks for your message. I was the principle author of the press release, so I will try to answer your question. I should note that the press release was reviewed by numerous scientists. But it was edited at NASA headquarters before it was made public.

      In my original draft, I purposefully avoided making the statement that the GRB was 7.5 billion light-years from Earth, because as your message implies, it is problematic to express specific distances when one is talking about events that happened in the very distant past, because the universe is rapidly expanding. Such is the case when trying to express a "distance" to GRB 080319B.

      The most relevant direct "distance" measurement is the object's redshift, which was measured to be 0.94. As the press release explained, this measurement tells astronomers how much the GRB's light was "stretched" by cosmic expansion. I used this popular website from a renowned UCLA cosmologist to convert the object's redshift to a light-travel time:

      http://www.astro.ucla.edu/~wright/CosmoCalc.html [ucla.edu]

      When I entered the redshift and the cosmological parameters based on the latest results from the WMAP satellite and large-scale galaxy surveys, the calculator gave me a light-travel time of 7.5 billion years. In other words, the light from this GRB was emitted 7.5 billion years ago.
      But at the time the burst occurred, Earth didn't even exist, so how does one express a "distance" between one object and another object that does not exist? In addition, 7.5 billion years ago, the visible universe was a much smaller place than it is now, because cosmic expansion has made the universe much bigger during those intervening 7.5 billion years. The GRB's host galaxy and the Milky Way Galaxy would have been much closer back then than they are today (please note that the Milky Way would have been a lot different back then, but it undoubtedly existed at that time). In fact, back then, the two galaxies would have been much closer than 7.5 billion light-years. And yet because of cosmic expansion, the two galaxies are currently much farther apart than 7.5 billion light-years. So there really is not an ideal way to express such a huge distance.

      In my opinion, the best way to express such a huge distance in a rapidly expanding universe at the level of a popular audience is to express distances in terms of light-travel time, which is what I did in the original draft of the press release. And because our best current measurements suggest that the universe is 13.7 billion years old, an event taking place 7.5 billion years ago is roughly halfway across the visible universe. Some of the scientists at NASA probably felt that it was important to specify a distance in a unit of distance rather than in a unit of time, so they translated the light travel time to a distance in light-years. I realize this is imprecise from a strict scientific perspective, but the NASA scientists concluded that there is no better way to express it, and I cannot think of a better way to do it.

      The problem, of course, is that the most precise way to express the distance is to state the redshift, which I did in the press release. Unfortunately, the term "redshift" has little meaning to the media and public, and the general public does not have the familiarity with astronomical terminology to be able to translate a redshift of 0.94 into a distance that has any deep meaning.

      Best regards,

      Robert Naeye, NASA Goddard Space Flight Center

  • by K. S. Kyosuke ( 729550 ) on Friday March 21, 2008 @04:51PM (#22823616)
    You do not believe me? Have you ever read The Star [wikipedia.org]? Yes, it is but a silly fantasy of mine, yet I shall paraphrase it nevertheless: "Oh Universe, there were so many stars in the Milky Way you could have used. What was the need to put a whole distant galaxy (with civilizations, perhaps) to the fire, that this giant fireworks (admittedly much more breathtaking than a mundane supernova) might honour the great writer having just passed away?"
    • Spooky... to be sure. Although Jesus only got the one star and civilization... does the great A. C. Clarke really deserve four including one MASSIVE one that could wipe out like a whole galaxy entirely?
  • "And THIS is the galaxy he lived in!..."

    *maniacal laughter*

"An organization dries up if you don't challenge it with growth." -- Mark Shepherd, former President and CEO of Texas Instruments