Learn facts about all 8 planets in our solar system. Compare sizes, distances, and characteristics. Free solar system explorer. No signup.
Our solar system contains eight planets spanning distances so vast that light takes 5.5 hours to reach Pluto (now a dwarf planet). Understanding the scale, composition, and characteristics of each planet provides essential context for astronomy, physics, and our place in the universe. Our guide covers all eight planets with key facts, size comparisons, and remarkable features.
Planet comparison by key metric: Largest planet: Jupiter — 1,321 Earths could fit inside. Smallest planet: Mercury — slightly larger than Earth's moon. Fastest orbit: Mercury — 88 Earth days per year. Slowest orbit: Neptune — 165 Earth years per year. Hottest surface: Venus — 465°C average (not Mercury despite closer to Sun — thick atmosphere). Coldest: Neptune — minus 200°C average. Most moons: Saturn — 146 confirmed moons as of 2026. Only planet to host life: Earth (confirmed).
Distance from Sun in light time: Mercury: 3.2 light minutes. Venus: 6 light minutes. Earth: 8.3 light minutes (1 Astronomical Unit). Mars: 12.7 light minutes. Jupiter: 43 light minutes. Saturn: 79 light minutes. Uranus: 160 light minutes. Neptune: 252 light minutes. Pluto (dwarf planet): 5.5 light hours. If Earth were a grain of sand 1mm diameter: Moon would be 30cm away, Sun would be 107 meters away, Neptune would be 3.2 km away.
Planets from closest to farthest: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Memory aid: My Very Educated Mother Just Served Us Nachos. Pluto was reclassified as a dwarf planet in 2006 by the International Astronomical Union because it has not cleared its orbital neighborhood — it shares the Kuiper Belt with similar objects.
Current scientific assessment: Mars: most feasible option — 24.6 hour day, some water ice, but 1% atmospheric density, no magnetic field, extreme cold. Requires significant terraforming or enclosed habitats. Venus: surface temperature 465°C and 90x Earth atmospheric pressure — essentially impossible. Gas giants: no solid surface. Europa (Jupiter's moon): liquid water ocean under ice shell — possible life but not habitable for humans.
Astronomers estimate 100-400 billion planets in the Milky Way galaxy. Based on Kepler telescope data: most stars have planets, many systems have multiple planets, and billions of planets may orbit in habitable zones. NASA's Exoplanet Archive has confirmed over 5,500 exoplanets as of 2026. The Milky Way itself is just one of an estimated 2 trillion galaxies in the observable universe.
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