4 ms·

About 10^46 J? In the classical approximation (1/2 Iω^2), assuming a uniform sphere of 2.0 solar masses and r=16 km. That's about 3% of the mass-energy (mc^2

About 10^46 J? In the classical approximation (1/2 Iω^2), assuming a uniform sphere of 2.0 solar masses and r=16 km. That's about 3% of the mass-energy (mc^2 = 3e47 J). This could be way off.

Crito 13y ago
Wolfram Alpha has 10^46 J as 100x the energy given off by a supernova. I don't know if that means your numbers are off, or if this star is just mind-bendingly insane.
- breischl 13y ago
  WA also puts the mass-energy of two solar masses at 3.574 x 10^47 J. So the initial calculation seems about right. My very-amateur-physicist guess is that the difference is because a supernova only converts a small fraction of the star's mass into energy - the remaining mass is thrown outwards to form planets and such. [1] - http://www.wolframalpha.com/input/?i=mass-energy+of+two+solar+masses http://www.wolframalpha.com/input/?i=mass-energy+of+two+sola...
- throwaway_yy2Di 13y ago
  Wikipedia suggests 10^44 J for type Ia, but 10^46 J for a more energetic core collapse: https://en.wikipedia.org/wiki/Supernova https://en.wikipedia.org/wiki/Supernova
- saalweachter 13y ago
  You can pack a lot of energy into a rotating system. You have similar problems with ring worlds or terraforming Venus (which barely rotates at all). Transporting in the extra hydrogen and all the rest is trivial compared to spinning it up to a decent period.
  - throwaway_yy2Di 13y ago
    I wonder if it's practical to store energy in rotating asteroids? For the terrestrial power grid. No friction, no (mechanical) safety hazards, just an expensive transmission problem. edit: Back-of-the-envelope says it's a very bad idea, which is just barely plausible if your asteroid is extremely large, and has an extremely high tensile strength (maybe iron-nickel?). Oh well. edit2: Also apparently there's a failure mode where if you do overestimate the strength of the asteroid's interior, it tears apart and (from e.g geosynchronous orbit) has a >5% chance of destroying most of the planet. D: Yeah, where I said "no mechanical safety hazards", I retract that.

About 10^46 J? In the classical approximation (1/2 Iω^2), assuming a uniform sphere of 2.0 solar masses and r=16 km. That's about 3% of the mass-energy (mc^2 = 3e47 J). This could be way off.

Crito 13y ago

Wolfram Alpha has 10^46 J as 100x the energy given off by a supernova. I don't know if that means your numbers are off, or if this star is just mind-bendingly insane.

breischl 13y ago
WA also puts the mass-energy of two solar masses at 3.574 x 10^47 J. So the initial calculation seems about right. My very-amateur-physicist guess is that the difference is because a supernova only converts a small fraction of the star's mass into energy - the remaining mass is thrown outwards to form planets and such. [1] - http://www.wolframalpha.com/input/?i=mass-energy+of+two+solar+masses http://www.wolframalpha.com/input/?i=mass-energy+of+two+sola...
throwaway_yy2Di 13y ago
Wikipedia suggests 10^44 J for type Ia, but 10^46 J for a more energetic core collapse: https://en.wikipedia.org/wiki/Supernova https://en.wikipedia.org/wiki/Supernova
saalweachter 13y ago
You can pack a lot of energy into a rotating system. You have similar problems with ring worlds or terraforming Venus (which barely rotates at all). Transporting in the extra hydrogen and all the rest is trivial compared to spinning it up to a decent period.
- throwaway_yy2Di 13y ago
  I wonder if it's practical to store energy in rotating asteroids? For the terrestrial power grid. No friction, no (mechanical) safety hazards, just an expensive transmission problem. edit: Back-of-the-envelope says it's a very bad idea, which is just barely plausible if your asteroid is extremely large, and has an extremely high tensile strength (maybe iron-nickel?). Oh well. edit2: Also apparently there's a failure mode where if you do overestimate the strength of the asteroid's interior, it tears apart and (from e.g geosynchronous orbit) has a >5% chance of destroying most of the planet. D: Yeah, where I said "no mechanical safety hazards", I retract that.