Astronomy is the scientific study of everything beyond Earth: stars, planets, moons, galaxies, and the vast space between them. Astronomers use telescopes and mathematics to understand how celestial objects form, move, and change over time.

Ancient astronomers tracked the patterns of stars and planets in the night sky, using their observations to create calendars and navigate across oceans. They noticed that while most stars seemed fixed in place, a few wandered across the sky. Modern astronomers have discovered that Earth orbits the Sun along with seven other planets, that our Sun is just one of hundreds of billions of stars in our galaxy, and that the universe contains billions of galaxies.

Today's astronomers study questions like: How did the universe begin? Are there planets around other stars that could support life? What happens when stars explode or when black holes collide? They work with enormous telescopes positioned on remote mountaintops or floating in space, and they use computers to analyze light that has traveled for millions or even billions of years to reach us.

Astronomy differs from astrology, which is the belief that the positions of stars and planets affect human behavior and future events. While astrology makes grand claims without evidence, astronomy uses careful observation and testing to understand our cosmic neighborhood.