11

Since hydrogen bombs detonating are like tiny little stars, I wonder what luminosity and spectral classification they would get if one were to categorize them like this. E.g. Starfish Prime and the Tsar Bomba?

John
  • 1,538
  • 6
  • 16

1 Answers1

16

Hydrogen bombs aren't like little stars. The process of fusion in stars is slow, releasing very little energy per cubic metre. As a result of this, and their large scale, stars are close to thermodynamic equilibrium throughout most of their interior and have a stable photosphere that can be characterised by a spectral type.

Further, stars contain a particular mixture of chemical elements in their photospheres, which conspire to produce many of the spectral features that give them their spectral classification.

In contrast, a fusion bomb will produce an expanding, cooling fireball that actually has more in common with a supernova explosion (indeed the Sedov blast equations, developed to model nuclear explosions, can also be applied to supernovae). The fireball itself might be considered as some sort of photosphere and as such, might be assigned some temperature, but that's about it.

Example of a fairly well-defined photosphere:

enter image description here

Screenshot from Operation Teapot - Tesla 28611. See December 7, 2017 Lawrence Livermore National Laboratory news release: LLNL releases newly declassified test videos

ProfRob
  • 151,483
  • 9
  • 359
  • 566
  • 1
    I see. Thank you. – John Jun 23 '21 at 07:12
  • I hope you don't mind the edit, these images are so compelling... – uhoh Jun 23 '21 at 07:30
  • 1
    So, type I supernova, or type II supernova? – Mark Jun 23 '21 at 20:55
  • 1
    And most of the energy of a 'hydrogen' bomb is actually from fission. Further, Teapot was not a thermonuclear device. – Jon Custer Jun 23 '21 at 20:55
  • @JonCuster hmm, the image was added by uhoh, but he could have included a picture of any fireball from an explosion – ProfRob Jun 23 '21 at 21:00
  • 2
    Re: "very little energy per cubic metre": One of my favorite fun facts is that per unit of mass, your body generates more power than the Sun does, by a few orders of magnitude. – Michael Seifert Jun 23 '21 at 21:04
  • @ProfRob - understood - just clarifying... – Jon Custer Jun 23 '21 at 21:20
  • The supernova explosions (looked from outside) happen on a timescale of hours or days so they are not a good analogy either. In a lot of them, the energy source is not something thermonuclear, but the gravity instead. – fraxinus Jun 23 '21 at 21:56
  • @fraxinus I believe the Sedov blast equations can be used to model certain phases of both. – ProfRob Jun 23 '21 at 22:10