By Alane Michaelson
Updated Mar 24, 2022
Image credit: ricardoreitmeyer/iStock/GettyImages
The Earth spins once every 24 hours, revolves around the Sun in 365.25 days, and the Moon orbits the Earth every 27.3 days.
The Sun is a middle‑sized, hydrogen‑rich star that fuels itself through nuclear fusion. It sits at the heart of our solar system and is the nearest star to Earth—one of more than 200 billion in the Milky Way. The Sun orbits the galactic center at roughly 220 km s⁻¹ (137 mph). It takes about 230 million years to complete one full galactic revolution.
Located third from the Sun, Earth orbits at an average distance of 149 million km (93 million miles). It rotates on its axis every 24 hours, producing the day/night cycle. The planet’s slightly elliptical orbit, combined with its axial tilt, drives the seasonal changes we experience each year.
The Moon is Earth’s only natural satellite, orbiting at an average distance of 384,000 km (239,000 miles). It takes 27.3 days to complete one orbit, and its synchronous rotation keeps the same hemisphere perpetually facing Earth. This relationship governs tides, and the alignment of Sun, Earth, and Moon produces eclipses.
Mercury completes a solar orbit in 88 Earth days, Venus in 225 days, Mars in 687 days, Jupiter in 12.1 years, Saturn in 29.5 years, Uranus in 84 years, and Neptune in 164 years. Only Mercury and Venus have shorter orbital periods than Earth.
For deeper insights, consult NASA’s official website or the Solar System Dynamics page.
