Astronomy Practice Exam

A nebula that consists mainly of hydrogen and helium is often a region where new stars are formed, also known as a stellar nursery. These nebulae are primarily composed of light elements, primarily hydrogen, and helium, which make up about 98% of the observable universe.

In addition to these gases, nebulae can also contain dust, which consists of tiny particles made up of metals and silicates, formed from previous generations of stars. The combination of gas and dust plays a crucial role in the processes of star formation, allowing gravity to collapse these materials into dense clusters that can ignite nuclear fusion and form stars.

The other options refer to different astronomical phenomena. Heavy metals are generally created in the cores of stars and released into the interstellar medium during supernova explosions, making them less prevalent in a typical nebula primarily composed of hydrogen and helium. Dark matter, while an essential component of the universe, does not interact with light and thus cannot be found in nebulae in the same way. Star remnants, such as white dwarfs or neutron stars, are the evolutionary products of stars that have reached the end of their life cycles, which is not applicable to a nebula still containing primarily hydrogen and helium.