Question

1. match the terms with the definitions.

light - year
the distance that light can travel in one year, or 9.5 trillion km
moon
a natural object that orbits a planet
solar system
the system including the sun and the natural objects that orbit it
planet
a large round object that orbits a star, does not orbit anything else, and has a clear orbit
galaxy
a system of millions to billions of stars, dust, and gas clouds

Explanation:

• galaxy: A galaxy is defined as a system of millions to billions of stars, dust, and gas clouds, so it matches "a system of millions to billions of stars, dust, and gas clouds".
• planet: A planet is a large round object that orbits a star (like the Sun) and has a clear orbit, not orbiting anything else, so it matches "a large round object that orbits a star, does not orbit anything else, and has a clear orbit".
• solar system: The solar system is the system including the Sun and the natural objects (like planets, moons, asteroids) that orbit it, so it matches "the system including the sun and the natural objects that orbit it".
• moon: A moon is a natural object that orbits a planet (like Earth's Moon orbiting Earth), so it matches "a natural object that orbits a planet".
• light - year: A light - year is defined as the distance that light can travel in one year (or about 9.5 trillion km), so it matches "the distance that light can travel in one year, or 9.5 trillion km".

Answer:

• galaxy - a system of millions to billions of stars, dust, and gas clouds
• planet - a large round object that orbits a star, does not orbit anything else, and has a clear orbit
• solar system - the system including the sun and the natural objects that orbit it
• moon - a natural object that orbits a planet
• light - year - the distance that light can travel in one year, or 9.5 trillion km