# How would a nuclear explosion look in vacuum?

Approximately, how does the specific luminosity, $L_\nu(t)$, of a nuclear explosion in a vacuum look as a function of frequency and more importantly, time? Assume the observer is very far away.

If this is difficult to answer, I still would like to know how long does the flash last and does it have a significant radio component? How about gamma rays? I would appreciate citations or a detailed/mathematical reasoning.

• What kind of nuclear explosion? Are we talking a fusion or a fission bomb? Or something different altogether? – probably_someone Jun 14 '17 at 23:53
• Let's say fusion. – Miladiouss Jun 15 '17 at 1:43
• In either case, anything more than a qualitative answer likely requires classified information. Though I can give a qualitative answer, if you want. – probably_someone Jun 15 '17 at 5:24
• Also, see related: physics.stackexchange.com/q/267819 – probably_someone Jun 15 '17 at 5:25
• My main goal is to see if we can identify extraterrestrial nuclear explosions. If so, what frequency. I think it would appear as a millisecond burst across a very wide spectrum, but that's just my intuition. I don't think an estimation would require classified information. Plus, this experiment has never been done. The closest thing is the atmospheric test which heats up their surroundings, hence their radiation can be dominated by thermal radiation of the gas around the explosion (which is not what I'm after). – Miladiouss Jun 15 '17 at 19:47

A partial answer: to figure this out, you might compare the energy in a typical nuclear explosion to the energy in a typical solar flare or coronal mass ejection, and spend some time reading about the visibility of these phenomena when they occur on other stars.

My instinct is that stellar eruptions are enormously more energetic than nuclear explosions, and still pretty tough to detect. I'll be interested to see whether you're able to be more quantitative.

• Solar flares are just hot plasma. They are not a fusing material. The reason they are hard to detect is that they happen next to an extremely bright object. – Miladiouss Jun 20 '17 at 0:44
• You are suggesting that a thermonuclear weapon (n.b. even our "fusion" weapons release most of their energy from fission) is not a hot plasma, and does not occur near a brighter object? – rob Jun 20 '17 at 4:57
• Solar flares are plasmas at 6000 K while a nuclear reaction wil be a plasma at 14000000 K! Plus, a nuclear fusion is not in thermal equilibrium, it may only emit in a very specific range. That energy, yes, may head up other particles, creating a hot plasma with thermal radiation. – Miladiouss Jun 21 '17 at 7:37
• @mpourrah - Solar flares are not 6000 K, that is the mean temperature of the photosphere. Solar flares occur in the corona and upper chromosphere. They are defined as localized (in time and space) enhancements in UV and X-ray flux, thus their "temperatures" are in the millions of degrees, not thousands. – honeste_vivere Jun 21 '17 at 16:43

In the early 1960s, the US military performed several nuclear test explosions in space, called Operation Fishbowl.

One of those explosions, Starfish Prime, created energetic particles that became trapped in Earth's radiation belts for decades.

In any case, there are numerous photographs of the explosions in the above linked websites.