Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics, physics, and chemistry in an effort to explain the origin of those objects and phenomena and their evolution

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.The word galaxy is derived from the Greek galaxias literally “milky”, a reference to the Milky Way.

Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.