Nuclear Explosion Space Bright or Dim Flash

[Albertgauss]

Hi all,

I think there is a post on this somewhere that is accessible via google but somehow too hard to find on this site. Anyway, if a nuclear explosion went off in deep space, I think the following would happen:

There would be a large burst of energy. All photons from Gamma to Radio would be emitted. The light from a nuclear blast is intrinsic to the energy of the nuclear explosion itself, so one should also see a bright fireball in the optical range. It should also persist for several seconds or more. A nuclear blast in the atmosphere of the Earth certainly persists for dozens of seconds, so I would expect a nuclear explosion in space to exist on a comparable timescale. It would be like a mini-sun for up to a minute, maybe 30 secs, I'm not sure, but it would be on this timescale.

There would also be Alpha and Beta rays, and neutrons, so there would be large numbers of these particles released. They wouldn't be seen with the naked eye, but they would cook anything nearby much more quickly and strongly than a microwave. Finally, there might be some heavier nuclei ejected from the nuclear erxplosion.

All expulsion of matter or photons would be spherical.

There would be no mushroom cloud, shockwave, sound, etc. as such effects would need an atmosphere, and that is completely lacking in deep space.

There would be heat, but it would NOT be due to the temperature of any gas; it would be the heat of the infrared photons produced by the energy of the explosion.

How am I doing with imagining what a nuclear blast would look like in space? Other posts on the internet mentioned a dim flash that is over quickly due to a lack of atmosphere, but I think this is incorrect. I think the trememndous energy in a nuclear explosion would have plenty of energy for plenty of optical photons.

 

[Bob S]

Google "Starfish Prime" to see video and color images of above-atmosphere nuclear shot.

 

[AdamLin]

I think that a few minutes after the blast you would have a lot of hydrogen gas. The neutrons can decay into protons that combine with the beta rays to form hydrogen.

 

[Bob S]

Much of the electrically-neutral matter (including neutral hydrogen and neutrons) would have multi-keV energies (β>0.005) or MeV energies and quickly escape the Earth's gravitational field. Most of the charged particles (including ions, protons, and electrons) would be trapped by the Earth's magnetic field, hit the upper atmosphere, and create spectacular Aurora Borealis. Gammas and x-rays would be line of sight into 4π.

 

[mfb]

"Deep space" is not close to the Earth - and starfish prime was still close to the earth.

>> The light from a nuclear blast is intrinsic to the energy of the nuclear explosion itself
But it comes from the primary explosion only, which is of the order of microseconds to milliseconds. Afterwards, you have a cloud of many isolated, fast particles expanding from the point of the explosion in all directions. Not many options to generate light.

A nuclear blast in or close to the atmosphere can heat the air, which can emit light afterwards.

>> All expulsion of matter or photons would be spherical.
You can design nuclear weapons to be aspherical. The total momentum is (in the frame of the warhead) zero, but it can emit more energy in two opposite directions, for example.

>> There would be no mushroom cloud, shockwave, sound, etc. as such effects would need an atmosphere, and that is completely lacking in deep space.
Correct

>> There would be heat, but it would NOT be due to the temperature of any gas; it would be the heat of the infrared photons produced by the energy of the explosion.
And all the other particles, as you already mentioned.

I think that a few minutes after the blast you would have a lot of hydrogen gas

Nuclear weapons produce a lot of neutrons in terms of nuclear reactions. But in terms of weight, don't expect more than some grams, rapidly flying in all directions. After one neutron lifetime, they are already (many) thousands of kilometers away from the explosion.