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Fermi and Swift Observe Record-setting Gamma Ray Burst 107

Posted by timothy
from the where-do-we-send-the-medal? dept.
symbolset writes "Phys.org shares a visual image of a 'shockingly bright' gamma ray burst observed April 27th, labelled GRB 130427A and subsequently observed by ground optical and radio telescopes. One gamma ray photon from the event measured 94 billion electron volts — three times the previous record. The burst lasted four hours and was observable for most of a day — another record. Typical duration of a gamma ray burst is from 10 milliseconds to a few minutes. Astronomers will now train optical telescopes on the spot searching for the supernova expected to have caused it — typically one is observed some few days after the burst. They expect to find one by the middle of May. The event occurred about 3.6 billion lightyears distant which is fairly close as gamma ray bursts go. Click on the GIF to view the actual burst."
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Fermi and Swift Observe Record-setting Gamma Ray Burst

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  • by mbone (558574) on Saturday May 04, 2013 @09:19PM (#43632301)

    The brightest Gamma ray bursts (GRB) are important for quantum gravity, as the photons have a short enough wavelength and go over long enough distances that spacetime foam [arxiv.org] should give them dispersion. The best test so far is based mostly on GRB 080916C [skyandtelescope.com], and from what I hear this new burst may be able to do better.

    A little background.

    The Heisenberg uncertainty principle predicts "virtual" particles. The time part of the uncertainty principle is delta T delta E > h, where E is energy, T is time and h is Planck's constant (I am ignoring factors of 2 pi). As the time of an event (say, the time for a photon to travel one wavelength) gets shorter, the energy of the virtual particles allowed (delta E) gets bigger. For short enough time periods (i.e., near the Planck time), the energy is enough that the virtual particles are black holes, popping in and out of existence, and severely mangling the spacetime on that time / distance scale. This mangling is called "spacetime foam". The wavelength of the GRB photons is much larger than the Planck distance (roughly, the virtual black holes should live for a Planck time and have an event horizon the size of the Planck distance), but the GRBs are very far away, and the GRB photons pass over many, many, Planck distances along the way, and each adds a little nudge. This effect depends on the photon energy (it is larger for higher energies, as these are smaller photons), thus the "dispersion" mentioned in these papers.

    The really cool thing is that the existing dispersion limits seem to be less than many people's expectations. If this is confirmed (and pushed down to a little smaller distance scale), then the conventional spacetime foam ideas I outlined above here may not be correct. This, in fact, may be the first evidence for the "holographic principle," which implies a smoother spacetime than the above ideas. In any case, this is the only way we have at present to say anything experimental about quantum gravity, so the more data the better.

  • by mbone (558574) on Saturday May 04, 2013 @10:31PM (#43632493)

    No. They may have detected something, and it's not gone through the pipeline yet, but Bert and Ernie were much before this event.

    They [lanl.gov] were August 8, 2011 (Bert) and January 3, 2012 (Ernie).

      Even if they didn't see a thing, I am sure there will be an IceCube press release about this in a few months, as they will be able to improve the GRB neutrino limit.

  • by StupendousMan (69768) on Saturday May 04, 2013 @10:55PM (#43632557) Homepage

    I wrote up a short summary of the observational details for one of my classes -- you can find it at

    http://spiff.rit.edu/classes/phys443/lectures/grb130427a/grb130427a.html [rit.edu]

    You can also follow a nice summary of the latest results by following Don Alexander's thread on the Cosmoquest forum:

    http://cosmoquest.org/forum/showthread.php?143754-GRB-130427A-burst-of-the-(quarter)-century [cosmoquest.org]

  • by femtobyte (710429) on Saturday May 04, 2013 @11:02PM (#43632581)

    "electron volt" is a unit of energy --- specifically, the energy required to move one electron charge across one volt of electrical potential. 1 joule is ~6.2*10^18 electron volts. And no, all photons aren't "equal" --- they have different energies (equivalently, different wavelengths, frequencies, momenta, or colors for visible-range photons). For comparison, visible light photons are ~2 electron volts energy.

  • by Baloroth (2370816) on Sunday May 05, 2013 @12:24AM (#43632807)

    They have a lot of directionality. The physics is not completely understood, but gamma ray bursts are focused along a fairly narrow line in two opposite directions.

  • wavelength (Score:4, Informative)

    by Spinalcold (955025) on Sunday May 05, 2013 @02:59AM (#43633215)
    To me one of the most surprising things is the wavelength. Back of the envelope calculation gives me 4.4 *10^-26m. That is amazingly small, 8 orders of magnitude smaller than the proton. This also came from 1/4 of the universe away, which makes me wonder how much smaller it is due to the expansion of the universe. Probably not much, but DAMN that is small.

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