Stars.

Stars are giant, glowing astronomical objects made of plasma—gas made of ions and electrons. Stars primarily consist of helium and hydrogen, and hold themselves together with gravity. The Sun is the star closest to Earth. Many stars are visible in the night sky, but these stars appear much smaller than the Sun due to their distance. Stars undergo a process called nuclear fusion throughout their existence, during which they fuse atoms together to produce energy. Some stars have life cycles of billions of years, while others only exist for a few million years. Stars vary in size, color, and luminosity, all of which determine what they become when they have reached the end of their life cycle.