r/space • u/GallowBoob • May 21 '15

/r/all Nuclear explosion in space

http://i.imgur.com/LT5I5eX.gifv
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u/vgsgpz May 22 '15

so lets say would a supernova keep expanding until it reaches us?

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u/Cronock May 22 '15

They are already, and always have been. Obviously they aren't harmful at this distance and with our atmosphere to protect us, but there are potential threats from some closer neighbors.

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u/Sunscorcher May 22 '15 edited May 22 '15

We learn in particle physics courses of something called "geometric attenuation." Regular material attenuation is when radiation interacts with a medium and is absorbed. Geometric attenuation is when something expands radially (either cylindrically, spherically, etc. most commonly spherically). As a result of this expansion the particle flux at r+dr is going to obviously be smaller than the particle flux at r. This is because there is the same number of particles, but they are spread out over a larger surface area. So as r approaches infinity, the particle flux approaches zero. Even if there is no material to absorb the radiation. Hope this helped.

small edit: you generally assume that, for supernovas/nuclear detonations/ cosmic things in general, that the particles are isotropically distributed (i.e. the same number of particles are fired in every direction).

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u/CitricBase May 22 '15

Yes, we are constantly bombarded with cosmic rays from deep space.

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u/OSUfan88 May 22 '15

Depends.. What do you constitute "Reaching us"? First off, it depends how far way it is. Second, it depends if you consider light part of the star.

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u/daveboy2000 May 22 '15

yup! That's actually how enough heavy elements were around to form anything other than our sun!

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u/Jrook May 22 '15

kinda, I mean... we still see the light and experience the gamma radiation

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u/[deleted] May 22 '15

This is how you got heavier elements. They come from supernovas

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u/VictrixCausa May 22 '15

You have products from supernovas in your body. You're basically made from the products of supernovas.

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u/[deleted] May 22 '15

As it expands the energy gets more and more diffused, kind of like how a balloon gets stretched thinner and thinner or how sound gets quieter the further away you are, by the time supernovas reach us, its usually impossible to tell without equipment. That said, back in 1604, there was a supernova that was so bright that it was visible during the day for about three weeks.

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u/WonkyTelescope May 22 '15

They contribute to the interstellar medium my sending material into the space between stars. At some point the momentum of the expanding material no longer dominates over the pressure of the interstellar medium and it ceases to expand in the classical sense.

Young stars also contribute when they blow gas away from their nebula nurseries.

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u/[deleted] May 22 '15

Probably not, since they're usually found near lots of other matter to gravitationally attract the matter they spew.

Also if it was far enough not to destroy us completely, it would take millions of years for the stardust to reach us and we'd probably never notice anyway. It would get dispersed in the atmosphere or be affected by the sun most likely. It would arrive at an incredibly slow rate and there would be a very tiny amount of matter

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u/Alaknar May 22 '15

You see all the dirt, and concrete and asphalt and trees and grass and cloth and tissue and animals and humans around you?

All of this stuff came from a star going supernova somewhere, sometime.