The Sun and Earth are both astronomical objects, but one is a star and the other is a planet. Comparing the Sun and Earth we see many differences: Stars like the Sun are balls of ionized gas, called plasma, engaged in thermonuclear fusion. Gas giant planets are balls of mostly gas that aren't massive enough to ignite the fusion process. Terrestrial planets like the Earth are of mostly solid and liquid composition that aren't massive enough to hold enormous atmospheres of gas. In the Sun-Earth relationship within the Solar System, the Earth orbits around the Sun at a distance of 93 million miles.