There are more than one layers of space and the second sun had been pushed beyond the first layer of space.
So the second sun was still at the same position. But there was now a barrier of space between it and the rest of the world.
The second sun is still denoted. It exploded into a great big ball of fire with enough power to incinerate most, if not all, of the Five Kingdoms. This meant that it had the power to kill millions of people and wipe out an area of land equal to five kingdoms or countries.
If Arthur had witnessed this explosion, he would be able to tell without a doubt that the explosion was enough to destroy a continent of Earth from his past life and punch a great big hole through the planet.
