What defines an 'exoplanet'?

• A. A planet that orbits within our solar system
• B. A planet orbiting a star outside of our solar system
• C. A moon that orbits a planet
• D. A celestial body created by asteroid collisions

Answer: (B)

An exoplanet is defined as a planet that orbits a star outside of our solar system. This definition is grounded in the distinct separation between our own solar system, which consists of the Sun and its gravitationally-bound planets, and other planetary systems that exist in the universe. Exoplanets are significant because they provide scientists with insights into the diversity of planetary systems and potentially habitable environments beyond Earth. The study of exoplanets can reveal important information about the formation and evolution of planets, as well as the possibility of life elsewhere in the universe.

The other options describe various celestial bodies that do not fit the specific criteria for exoplanets. Planets within our own solar system, moons orbiting planets, and celestial bodies resulting from asteroid collisions all fall outside the definition of exoplanets, which requires the planet to be in orbit around a star that is not the Sun.