What is a nebula?

A nebula is best defined as a giant cloud of gas and dust in space. This definition is grounded in the fact that nebulae can be regions where new stars are born or the remnants of dead or dying stars. They play a crucial role in the life cycle of stars, as the materials within nebulae can condense under the force of gravity to form new stars and planetary systems. Additionally, nebulae can exhibit a range of compositions, including hydrogen, helium, and other ionized gases, as well as dust particles.

This understanding places nebulae as fundamental components in the structure of the universe, contrasting sharply with other options such as a type of star, black holes, or alignments of stars, which do not accurately encapsulate the nature and function of nebulae in astronomical studies.