A planetary nebula is an astronomical object formed when a star similar to the Sun exhausts its nuclear fuel. As the star ages, it expands into a red giant and eventually sheds its outer layers, creating a glowing shell of gas and dust. The remaining core, now a white dwarf, emits ultraviolet radiation that ionizes the expelled material, causing it to shine brightly. These nebulae are typically round in shape and can vary in color, depending on the elements present. They are often short-lived, lasting only a few thousand to tens of thousands of years before dispersing into space, contributing to the formation of new stars and planets.