Illustration of the solar system with lunar phases

Space and the cosmos refer to the vastness of the Universe and all the celestial bodies within it: stars, planets, moons, galaxies, comets, and many other objects. Their study falls primarily under astronomy, a science that began with humanity's earliest observations of the sky. Since ancient times, civilizations have observed the stars and the movements of celestial bodies in order to better understand the Universe around us.

The sun is the star at the center of our solar system.It is a hot ball of gas, mostly hydrogen and helium, that gives Earth light and heat.People use sunlight for warmth, growing food, and solar power, and they have long watched it to track seasons and time.

A planet is a large body that orbits a star.It can be made of rock, ice, or gas, and may have moons or rings.In our Solar System, eight planets orbit the Sun, and some are visible in the night sky and have been known since ancient times.

The Moon is Earth's only natural satellite.It is the fifth-largest satellite in the Solar System and the largest relative to the size of its planet.Its gravity causes ocean and body tides and slightly lengthens Earth's day.