Astronomy Practice Exam

What is the primary characteristic of a moon?

1. A small object that generates its own light

2. An object that orbits a star directly

3. An object that orbits a planet

4. A large object that orbits a galaxy

The correct answer is: An object that orbits a planet

The primary characteristic of a moon is that it is an object that orbits a planet. Moons are natural satellites, meaning they are objects that orbit a celestial body that is itself in orbit around a star. This relationship distinguishes moons from other celestial objects, such as stars, which generate their own light, and planets, which orbit stars directly. Moons can vary greatly in size and composition, and they do not emit light; instead, they reflect the light of their parent star, which is typically the Sun in our solar system. Understanding this definition allows for distinguishing moons from the broader context of celestial objects. For instance, options describing objects that generate their own light or those that orbit a star directly do not capture the essence of what constitutes a moon, nor do descriptions that suggest they orbit a galaxy, which pertains to larger cosmic structures. Thus, identifying moons specifically as objects that revolve around planets is fundamental to their definition and role in astronomy.