Fermi and Swift Observe Record-setting Gamma Ray Burst

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."

Comments

This may be important for quantum gravity

[mbone]

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 should give them dispersion. The best test so far is based mostly on GRB 080916C, 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.

Re:This may be important for quantum gravity

[Ultra64]

Mmm, hmm. I recognize some of these words.

Re:This may be important for quantum gravity

[Baloroth]

Really? Is slashdot now making fun of the nerds for being smart?

You must be a ton of fun at parties. In this case, the poster is actually making fun of *himself* for not being as smart as the OP (or, possibly, simply for not being educated in the field the OP is talking about), not of the OP for being smarter than him. At worst, it is a comment on how specific and arcane the language of a specific field can become to the outside observer.

Re:This may be important for quantum gravity

[mbone]

No, although that was entertained (by some) in the fairly long history of these bursts.

In the early days (after GRB were detected by US satellites sent up to look for nuclear explosions) there were lots of theories, as we knew basically nothing about them. The consensus was that GRB were probably fairly close to us, in the galaxy (which kept the burst energy reasonable). The early satellites could only see the brightest bursts, so there weren't many bursts observed, and statistics were very poor, so you couldn't say much more. (At this time I remember some people proposing primordial black hole explanations.) One of the major goals of the Compton Space Telescope BATSE experiment was to be sensitive enough to GRB to be able to observe hundreds to thousands of them, with decent positions, enough data so that you should be able to see the Milky Way (the galactic disk) in the burst locations (i.e., that you would see more bursts along the Milky Way in the sky than in other directions). At the time, the consensus opinion was very strongly that BATSE would see the plane of the Milky Way in the aggregate burst positions, as they accumulated.

The experiment was flown and worked well and recorded an isotropic (random) distribution of bursts. (So much for conventional wisdom.) This meant that the bursts were either very far away (and thus very powerful) or very close (and thus relatively weak, weak enough that you could only see them up to a few light years, where everything is in the galactic disk, and thus can look random in direction, the way the brightest stars in the night sky appear more-or-less random in direction). I actually toyed around with an extraterrestrial intelligence explanation for close bursts at that time (the bursts would be some side effect of power generation or space travel, which would have implied that the ETIs were close and ubiquitous), but most people started thinking about extremely distant (to be random), and thus very powerful events. (IIRC, this was bad but not quite fatal for the primordial black hole explanation, as those bursts are strong enough that you would expect to see the galactic disk in the accumulated BATSE data, but maybe you could adjust things enough to get around that.)

This conundrum was resolved by the orbiting Swift telescope, which could not only see GRB, but could report a position back to Earth quickly enough to train an optical telescope on the spot within a few seconds. This was flown, and some GRBs were observed in the optical. (This also required some serious work on rapid response optical telescopes.) Swift + optical meant that we knew their positions very accurately, so the biggest telescopes could be used to see where, exactly, they were coming from (which turned out to be distant galaxies) and thus get a red shift, and thus a distance (the GRB of the OP is apparently at a red shift of 0.34). That, among other things, showed very clearly that these bursts could not be primordial black holes (or local ETI!), as those are much too weak to see bursting across cosmological distances.

New low for slashdot

[Anonymous Coward]

It happened 3.6 billons of years ago, isn't time to get a bit fresher news?

A page with technical details

[StupendousMan]

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

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