I'm very curious about this : if the Sun were to become a white dwarf, would Earth get blasted with high-energy electromagnetic radiation? I know that current predictions say that Earth will be destroyed during the Sun's red giant phase, but if we assume it survived, would gamma rays rain down on Earth's surface?
My guess is that we would receive high-energy rays from the nuclear reactions still occuring inside the core, right before the star's explosion, but I'm not sure...
There is no great explosion in the formation of a white dwarf.
The outer layers of the star are blown off into space, forming a "planetary nebula" and the dense carbon-oxygen core remains. The core is pretty hot (100,000 degrees) Hot enough to radiate X-rays, but not the more energetic gamma rays. The Earth (assuming that it is still in an orbit) will have had its atmosphere stripped by the power solar wind and will now be subject to this X-radiation.
There are no nuclear reactions occurring in a white dwarf. The temperature is not enough to begin carbon fusion so the white dwarf star will slowly (over billions of years) cool down.
Perhaps you are confusing the formation of a white dwarf with a supernova explosion of a more massive star. If a supernova were to occur at the distance that the sun is from Earth, the Earth would pretty instantly be vapourised.
