Our solar system consists of the Sun, eight planets, their moons, and many smaller objects. The four inner planets (Mercury, Venus, Earth, Mars) are rocky. The four outer planets (Jupiter, Saturn, Uranus, Neptune) are gas or ice giants.

Earth rotates on its axis once every 24 hours, creating day and night. It revolves around the Sun once every 365.25 days, creating a year. The tilt of Earth's axis (23.5°) causes the seasons as different parts of Earth receive varying amounts of sunlight throughout the year.

Stars are massive balls of hot gas that produce energy through nuclear fusion. Our Sun is a medium-sized star. Stars vary in size, temperature, color, and brightness. They go through a life cycle: nebula → main sequence star → red giant → white dwarf (or supernova for massive stars).

Our galaxy, the Milky Way, contains billions of stars. The observable universe contains billions of galaxies.