Astronomy Practice Exam

Which of the following describes a planet’s light source?

1. Generates its own light

2. Shines by reflected light

3. Does not produce any light

4. Absorbs light from stars

The correct answer is: Shines by reflected light

The correct answer, which states that a planet shines by reflected light, accurately describes how planets appear to us in the night sky. Unlike stars, which generate their own light through nuclear fusion, planets do not create light independently. Instead, they reflect the light emitted by their parent star, most notably the Sun. This is why we can see planets; they are illuminated by sunlight that bounces off their surfaces and travels to our eyes. In contrast to the other options, planets do not generate light themselves; they do not have any internal mechanisms to produce light like stars do. While it is true that they do not absorb light in a way that would contribute to their visibility (as absorbing light would not help them shine), they reflect light rather than generating or emitting it, which aligns with the nature of celestial objects classified as planets.