The stars are the most distant objects that can be seen with the naked eye. They are massive spheres of gas and dust that are held together by their own gravity and emit light from the energy produced by nuclear fusion in their cores. Stars range in size from small red dwarfs to supergiant blue stars, and come in a variety of colors, including red, blue, yellow, and white. Stars can be found in clusters, called constellations, or alone in the night sky. They have been used for navigation since ancient times and continue to inspire awe and wonder today.