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I think our radiation shield wouldn't last long. Back of the envelope, just for fun: supernova type Ia energy release: ~ 1e44 Joules [1] radius of Earth orbit

I think our radiation shield wouldn't last long. Back of the envelope, just for fun: supernova type Ia energy release: ~ 1e44 Joules [1] radius of Earth orbit, m: ~ 1.5e11 meters diameter of Earth, m: ~ 1.27e7 meters mass of Earth: ~ 5.9e24 kg average specific heat of Earth (assume it's all granite): 2,000J/kg/°K Grinding through the above says that if the Sun went supernova of the wimpiest type, it would dump 1e44 Joules to its surroundings. I think this happens pretty fast, say less than an hour or so. Assuming isotropic distribution, the Earth would intercept about 4.5e-10 of that, or about 4.5e34 Joules. That's enough to heat the entire mass of the Earth to ~ 3.8e6°K. That would literally vaporize the entire Earth. There goes our radiation shield. Never mind the supersonic shock coming through the planet from the ablation blow-off on the side facing the supernova. Amazing and hard to imagine... [1] https://en.wikipedia.org/wiki/Supernova#Energy_output https://en.wikipedia.org/wiki/Supernova#Energy_output

Santosh83 10y ago
Awesome. But IIRC even our Sun expanding into its red giant phase should be sufficient to vaporise the Earth, at least according to some models, while other models say everything up to Venus will be vaporised while Earth will be left as a charred lump. More interesting is the case of a supernova within ~100 light years.
Retric 10y ago
Planets are going to act like an ablative heat shield so it's not quite that simple, however yea even if you survive the initial event it's going to cook any fragments that would otherwise make it. Also, supernova don't just toss out radiation, the kinetic energy imparted to the outer layers of hydrogen is ridiculous.