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Furthest Gamma-Ray Burst Ever Observed

Posted by ScuttleMonkey on from the really-really-old-news-that-is-new-to-us dept.

jd writes "The SWIFT team have announced the furthest-ever observed super-massive gamma-ray burst (from 13 billion light years away). The burst was observed on the 6th of September and lasted for 3 minutes - long enough for a number of other telescopes to home in on the gigantic explosion. The distance is only barely within the reaches of the observable universe. The idea of the SWIFT telescope and follow-up observations is that they will discover both the cause of the bursts and the consequences to the star."

4 of 273 comments (clear)

  1. NOVA ran a program on gamma ray bursts... by Propagandhi · · Score: 5, Informative

    Imagine there are a few people rather lost at the headline (we're not all astronomers/cosmologists/whatever :) ). Anyway, NOVA ran an excellent show on this a couple years ago, and as usual there was an excellent companion website.

    If that doesn't answer your questions, well... there's always Wikipedia. /I feel like a Karma whore linking to wikipedia, mod me as you see fit..

    1. Re:NOVA ran a program on gamma ray bursts... by Michael+Woodhams · · Score: 5, Informative

      Here's the simple answer:

      About 13.5 billion light years ago, the universe changed from being opaque to photons to being transparent (an event inappropriately called "recombination"). No photon emitted earlier than this time could reach us, so we cannot observe further than about 13.5 billion light years away. (The photons emitted at that time are the cosmic microwave background.) So the observable universe is 13.5 billion light years in radius. A billion years from now, it will be 14.5 billion light years in radius.

      However, it gets more complicated: the universe is expanding, so the space that photon travelled through has got bigger in the meantime.

      Imagine two points in the universe. Because the universe is expanding, the distance between them is increasing with time. The rate at which the distance increases is a velocity (which you can think of as causing the red shift of distant galaxies.) Hubble's law says this velocity is proportional to the distance between them. If they are sufficiently distant, the relative velocity is greater than the speed of light.

      So (for example) imagine this is twice the speed of light. A photon emitted from one point travels towards the other. After one year, it has travelled one light-year, but the points have got two light-years further apart - clearly it will never arrive. These two points are not in each other's observable universes. The edge of our observable universe are the points which have a recession velocity equal to the speed of light.

      The discussion above assumes no acceleration. Of course, astronomers from Hubble onwards knew there would be acceleration, but it wasn't until the mid 1990s that we could measure it.

      It turns out, contrary to general expectation, that the expansion of the universe is now accelerating. This means that as time goes on, points don't have to be so far apart before their recession velocity exceeds the speed of light, so in a sense the observable universe is getting smaller. (In the sense that points that were within our observable universe in the past are no longer so. But remember that the points are always getting further apart - the radius of the obserable universe is increasing linearly with time.)

      I am an ex-astronomer, not a cosmologist. There may be subtle errors in the above, but I hope not.

      --
      Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
  2. Re:An honest question... by Peyna · · Score: 5, Informative

    How do we know the universe is 13.7 billion years old? It was recently discovered that the universe's expansion is accelerating as time goes by. Assuming this change in acceleration has been the case all along, doesn't that really fudge with the numbers we used to estimate the universe's age?

    There are many ways to estimate the age of the universe, not all of which involve calculating the expansion of the universe.

    http://www.astro.ucla.edu/~wright/age.html

    --
    What?
  3. Re:light instead of gamma by UnrefinedLayman · · Score: 5, Informative

    For being so feisty, are you quite sure there's no such thing as alpha and beta radiation?

    http://www.orau.gov/reacts/alpha.htm

    http://www.orau.gov/reacts/beta.htm

    Both are particle radiation and both plentifully originate in stars. You can read more about them in Wikipedia also.

    http://en.wikipedia.org/wiki/Particle_radiation