Slashdot Mirror
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."
How close would one of these events have to be to us to fuck us up?
If Slashdot were chemistry it would look like this:Cadaverine
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.
Will this have any effect on the Man-in-the-Moon Marigolds.
Could this be Betelgeuse? Did we just dodge that bullet?
Men's only, of course.
It happened 3.6 billons of years ago, isn't time to get a bit fresher news?
There was a story about it here when it first happened.
How can a photon have volts? Aren't all photons created equal?
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
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
I thought we dodged Betelgeuse in 1988.
Aren't all photons created equal?
No, that was the early black and white universe: for the last 13.8 billion years we've had colour.
I have just imagined http://en.wikipedia.org/wiki/Enrico_Fermi and http://en.wikipedia.org/wiki/Jonathan_Swift looking at a supernova. Maybe someone can guess what they would say to each other about it, but I have no idea.
Contrary to the popular belief, there indeed is no God.
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.
a long time ago...The Death Star destroyed a planet, and here is the result, a sudden disturbance in the Force.
Google passes Turing test : see my journal
The article says it is 3.6 billion light years away. But when is that distance applicable? This event happened long, long ago and we are just now seeing it. But was the 3.6 Gly the distance back when it happened? Or is the 3.6 Gly the distance today, when we see it? Given the purported expansion of the universe, this matters.
We can see these past events happen because they were far enough away when they happened. We cannot see most recent events because the light has not gotten here yet (unless the event happens nearby, such as asteroid fragments slamming into a big gaseous planet). We cannot see event events that are even longer back in the past because their light has already gone past us. And, of course, we cannot see the big bang and all the fireworks that happened shortly after it because its light (supposedly) just went out away from all the mass that emerged. There should be an outer boundary/edge where the mass has reached. There should also be an outer boundary/edge of where we can see events that happened at some chosen past time, the furthest being for the time frame back to the big bang. But science has not really explained all this.
Given the point in space where we are today, which direction should we have looked at, if we were here when the light of the big bang passed this point, to have seen it?
One big question is, how far back can we see. We cannot see back to the big bang, so there is a limit, if we confine the question to seeing events within the mass that emerged from the big bang. And how far away is that?
now we need to go OSS in diesel cars
A long time ago (3.6 billion years to be precise) in a far away galaxy (3.6 billion light years away to be precise), people died.
I see already some politicians in the US asking for a military intervention to all possible supernovae as they are an external treat to the US...