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Astronomers Detect Record-Breaking Gamma Ray Bursts

smithsonianmag.com

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Re: Astronomers Detect Record-Breaking Gamma Ray Bursts

#31

Post by sathackr »

torben-friis wrote: post #28
maxnoe wrote: post #23

Earlier quoted context omitted.

Doesn't really make sense to speak of wavelengths at these energies any more. For all intents and purposes, these are particles. The energies we detect go into the hundreds of TeVs and charged cosmic rays have been detected to much, much higher energies.

the transition/duality of particles and waves is something that, despite having heard about it many times, I'm still unable to grasp intuitively

I'm still not grasping it either, to the point that I feel we may eventually learn they are neither, something else that looks to us sometimes like a particle and sometimes like a wave.

Re: Astronomers Detect Record-Breaking Gamma Ray Bursts

#32

Post by strainer »

maxnoe wrote: post #24
salawat wrote: post #14

Earlier quoted context omitted.

I think it does actually. A gamma ray is just light, we would expect the signal to get attenuated early on in the atmosphere. This particular one had enough oomph to punch down to ground level instruments and actually generate a response. Either it lucked out statistically and had a momentary straight shot to the ground (I mean, it could happen), or the thing had so much energy it ploughed straight through anything t…

This is not really how things work. We are talking about single particles of light having energies between ~ 50 GeV and up to 10 TeV (for this GRB, other sources go even higher). At these energies, the atmosphere is completely opaque and the gamma rays are absorbed at around 20 km height. However, the process kicks of a cascade of particles, the gamma ray is absorbed by creating an electron-positron pair, each with h…

Ah so effectively none of the Hev photons reach the ground. I see the papers include the "Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes" data. I wouldn't have expected imaging to be practical because cherenkov is kind of scattering, but they seem to be able to triangulate individual collisions. Thanks for the correction.

Re: Astronomers Detect Record-Breaking Gamma Ray Bursts

#33

Post by maxnoe »

sathackr wrote: post #31
torben-friis wrote: post #28

Earlier quoted context omitted.

the transition/duality of particles and waves is something that, despite having heard about it many times, I'm still unable to grasp intuitively

I'm still not grasping it either, to the point that I feel we may eventually learn they are neither, something else that looks to us sometimes like a particle and sometimes like a wave.

We already did learn that. QED describes a photon perfectly mathematically.

There is just now word that maps that to ordinary terms.

Re: Astronomers Detect Record-Breaking Gamma Ray Bursts

#34

Post by maxnoe »

strainer wrote: post #32
maxnoe wrote: post #24

Earlier quoted context omitted.

This is not really how things work. We are talking about single particles of light having energies between ~ 50 GeV and up to 10 TeV (for this GRB, other sources go even higher). At these energies, the atmosphere is completely opaque and the gamma rays are absorbed at around 20 km height. However, the process kicks of a cascade of particles, the gamma ray is absorbed by creating an electron-positron pair, each with h…

Ah so effectively none of the Hev photons reach the ground. I see the papers include the "Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes" data. I wouldn't have expected imaging to be practical because cherenkov is kind of scattering, but they seem to be able to triangulate individual collisions. Thanks for the correction.

We basically see a blob of light from which we can deduce origin, energy and particle type of the particle that created the air shower.

If you have multiple telescopes observing the air showers this gets much better. MAGIC uses two 17m telescopes, VERITAS 4 12 m telescopes and HESS 4 12m and one 28 meter telescope.

CTA is currently in the planning and construction phase and will build around a hundred telescopes at two sites, Chile and La Palma.

Re: Astronomers Detect Record-Breaking Gamma Ray Bursts

#35

Post by ncmncm »

maxnoe wrote: post #21
ncmncm wrote: post #17

Earlier quoted context omitted.

First time for any galaxy, that we know of.

No, not really. We are talking here of the first time a short burst of only a few minutes was detected from a source not previously known. Distant galaxies with super massive black holes in their center are a well known source of this kind of gamma radiation. Known as active galactic nuclei and especially blazars

First time this energetic, by an order of magnitude.

The suggestion is that they were produced by a different process that concentrated energy more than the usual sources.

It's not hard to get more total energy released, just by being bigger. To concentrate more energy into individual photons requires more intense processes.

A black hole crashing into a magnetar would cause unusually intense activity for some while.

Re: Astronomers Detect Record-Breaking Gamma Ray Bursts

#36

Post by ncmncm »

tannhaeuser wrote: post #22
ncmncm wrote: post #15

Earlier quoted context omitted.

Depends on the GRB. A supernova 50 light years away is supposed to eliminate all large animal life (including us). Fortunately any stars capable of it are more than 100 Ly away, where they would only eliminate, e.g., civilization. A magnetar quake 500 light years away would sterilize the planet (but not harm the magnetar at all). Fortunately, the nearest magnetar we know about is 9000 light years away, so its blast w…

What about Eta Carinae?

It's very pretty. And already blew.

Re: Astronomers Detect Record-Breaking Gamma Ray Bursts

#37

Post by ncmncm »

ajuc wrote: post #27
ncmncm wrote: post #15

Earlier quoted context omitted.

Depends on the GRB. A supernova 50 light years away is supposed to eliminate all large animal life (including us). Fortunately any stars capable of it are more than 100 Ly away, where they would only eliminate, e.g., civilization. A magnetar quake 500 light years away would sterilize the planet (but not harm the magnetar at all). Fortunately, the nearest magnetar we know about is 9000 light years away, so its blast w…

Are these threats so sparse in the whole universe, or is our region special? Is it unlikely that we are far enough to be mostly safe from these threats? Or maybe it's one filter for Fermi paradox (on a planet that isn't far from these kinds of threats life wouldn't survive long enough to develop civilization).

There are myriad^n places in the universe where such threats are infrequent enough for civilization to operate for millions, even billions of years.

The Fermi paradox needs another filter. Some people think it is that interstellar civilizations that arise come into contact with one another, destroying both.

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