What would happen if Betelgeuse went supernova?

Betelgeuse is 160 parsecs (520 light years) distant. If we just consider what could happen as a result of its expanding shell of gas, typical shell velocities are about 10,000 kilometers/sec. The shell would arrive here about 100,000 years after we see the star brightened. The shell would carry perhaps 10 times the mass of the Sun or some 2 x 10^58 protons. The flux of particles in a shell with a radius of 160 parsecs would be about 140,000 protons per second per square centimeter. The solar wind flux, by comparison is about 300 million protons/sec/square centimeter at the Earth's orbit. So, although detectable, the flux from Betelgeuse probably won't do much biological damage compared to what the Sun does. However, because the Betelgeuse flux is traveling at 10,000 kilometers/sec compared to the 450 kilometers/sec of the solar wind, the Betelgeuse flux has an effective pressure that is (10,000/450)^2 = 490 times stronger than the solar wind, and spread out over a region much larger than the size of the solar system. This would probably cause the Sun's magnetopause to collapse from its present radius near 100 AU, to possibly less than the orbit of the Earth. Also, the Earth's magnetosphere would be compressed, which would cause the energies of the particles in the van Allen belts to be amplified. The environment outside the van allen radiation belts would probably be 'lethal' for human exploration of the solar system.

There is also the x-ray flux to contend with. Inside this shell, which would probably take many decades to pass by, there is a bubble of plasma consisting of electrons and magnetic fields which produce copious amounts of X-ray light. We would be subjected to this x-ray flux for 10s of thousands of years until the expanding supernova remnant has aged sufficiently to quench this production mechanism. These X-rays, of the 'soft' variety' would not get down to the Earth's surface thanks to atmospheric shielding, but travelers in interplanetary space would need some additional shielding from the secondary electrons generated as these x-rays strike the skin of their spacecraft and liberate additional electrons.


Copyright 1997 Dr. Sten Odenwald

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