What are the giant clouds spread throughout a galaxy called?

The term used to describe the giant clouds spread throughout a galaxy is "nebulae." Nebulae are vast regions of gas and dust in space, and they can serve as both the birthplace of new stars and as remnants of dead or dying stars. They often contain hydrogen, helium, and other ionized gases, and their size can vary significantly, ranging from a few light-years to several hundred light-years across.

In the context of galaxies, nebulae are critical components because they are responsible for star formation. When regions within a nebula become dense enough, gravity can collapse these regions to form new stars and potentially planetary systems around them. Nebulae often appear visually stunning when viewed through telescopes, showcasing varied colors and structures due to the different gases and dust present.

The other terms listed do not accurately describe these vast cosmic structures. Stars are the luminous objects formed from the dense regions of nebulae. Planets are celestial bodies that orbit stars and are formed from the material left over after star formation. Dust clouds, while related, are not the specific term used for these extensive clouds associated with star formation and are more of a component within nebulae rather than a classification of them. Thus, the correct choice encompasses