The sun is an object denser than earth. We know it is denser because it has a higher equilibrium than earth within the UA. Its regular cycles are the effects of residual motion. The pressure of the UA has squished the sun so that the top and bottom are nearly flat. The bottom surface is dense, flat, and highly reflective. As the heat, which comes from the core of earth, dissipates towards the sun it is reflected off the surface. This is why sunlight is percieved as "warm." Most of this infrared light is changed due to the acceleration of the earth and sun, as well as atmospheric effects into visible light.
There, much more likely than a giant bomb that is fueled, detonated but refuses to explode.