Remaining nebulae are clouds of gas and dust in space that are left over from the formation of stars. These nebulae can be remnants of supernova explosions, where a massive star has ended its life cycle, or they can be the leftover material from the birth of new stars. They play a crucial role in the life cycle of stars and the evolution of galaxies. Some well-known examples of remaining nebulae include the Crab Nebula and the Ring Nebula. These structures are often studied by astronomers to understand the processes of star formation and the chemical enrichment of the universe. Remaining nebulae can also be sites where new stars are born, continuing the cycle of stellar evolution.