A system of planets and other bodies that orbit a star.

A system of planets and other bodies that orbit a star.

• A. Milky Way
• B. Solar System
• C. Galaxy
• D. Universe

Answer: (B)

A solar system is defined by a star at the center whose gravity holds together a group of bodies that orbit it, including planets, moons, asteroids, and comets. That star–orbiting arrangement is exactly what this description points to, with the Sun being the central star in our own example. Other stars can have their own planetary systems as well, but the general idea remains the same: a gravitationally bound group of objects orbiting a star. In contrast, a Milky Way is a galaxy—an enormous collection of billions of stars and much more matter; a galaxy is not a single star’s orbiting system. The universe includes all of this and more. So the term that fits best is the solar system, the star-centered family of orbiting bodies.

A solar system is defined by a star at the center whose gravity holds together a group of bodies that orbit it, including planets, moons, asteroids, and comets. That star–orbiting arrangement is exactly what this description points to, with the Sun being the central star in our own example. Other stars can have their own planetary systems as well, but the general idea remains the same: a gravitationally bound group of objects orbiting a star. In contrast, a Milky Way is a galaxy—an enormous collection of billions of stars and much more matter; a galaxy is not a single star’s orbiting system. The universe includes all of this and more. So the term that fits best is the solar system, the star-centered family of orbiting bodies.