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hundenkattenglassen t1_je9bljq wrote

Reply to comment by Ivedefected in The brightest gamma-ray in human history hit our planet this past Fall by PuzzleheadedOne1428

Pretty fukin amazing that a few thousands light years is considered to be a dangerous area within GRB range.

Meanwhile on Earth and large explosions, meh go 10 km away and you’re perfectly safe from any man made non-nuclear explosions.

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potatomafia69 t1_je9zote wrote

More specifically under 150 lightyears. Cancer rates will skyrocket, ozone layer will be depleted and it could even trigger an ice age. Under 25 lightyears is just a death sentence. It'll cause mass extinction of almost all life forms on Earth. Luckily there's not one star that will go supernova anytime soon within this radius and there's not much to worry about.

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drailCA t1_jeaujyx wrote

Betelgeuse is the closest at 650 lightyears from my understanding.

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potatomafia69 t1_jeav3hp wrote

The closest one that'll go supernova in the near future. There are a couple of other candidates as well in the far future.

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jdragun2 t1_je9z1eg wrote

They have to be basically pointed directly at us to be a threat. The chances of one being in the correct range and be directly lined up with our solar system [I'm pretty sure they would be large enough to encompass most of the inner solar system in a beam] is outlandishly small. A few seconds difference and a beam would miss completely at those distances thanks to how fast everything is moving relative to one another at that scale. The fact that this one hit from the distances it did is mind boggling. I also wonder about how much diffusion of the beam there is over those distances, which if it did, would it increase the chances of getting hit or decrease it? Any astrophysics people who would like to chime in here I would appreciate it!

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bluesam3 t1_jeab7wk wrote

Not an astophysicist, but I can give a lower bound: the lower limit limit on beam divergence angle is (wavelength) / (πœ‹ Γ— (initial diameter)). Wikipedia suggests a source diameter of ~60,000 km, and the peak photon energy for the event was 18 TeV, which translates to a wavelength of about 7Γ—10^(-20)m, putting the lower limit on divergence (for a perfect laser) at 7Γ—10^(-20)/(πœ‹ Γ— 60000000) = 372 nanoradians, which gives a final radius at that range of 60000km + 2 Γ— sin(372 nanoradians) Γ— (2.4 billion light years), which works out to somewhere in the region of 1,800 light years. This beam was presumably a very long way away from being a perfect laser, and most of the particles will have had lower energies, so that's probably an order of magnitude or several too low. However you slice it, though, that's a pretty wide end target, so it's probably more accurate to say it hit our vague region of the galaxy, rather than that it hit Earth. Certainly it wasn't at risk of hitting the wrong bit of the solar system.

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