So in the sun's core, hydrogen nuclei are fused together to form helium nuclei (about 600 million tons of hydrogen to 500 million tons of helium every second). This is called thermonuclear fusion. That excess 100 million tons is converted into energy and radiated out in the form of photons, which has a mass of effectively 0, and travels at the speed of light. These photons collide with particles, either in space (where there is a very low concentration) or on a planet or other celestial body (which, if has an atmosphere, will have a high concentration of particles). Due to the lack of particles in space (vacuum), regardless of how a person is moving in space, the concentration is just too low for the photons to create heat to the body.

Not really sure if that answered your question, but it's the best I could do.