The Sun
G-type main-sequence star
Our star holds 99.8% of the system’s mass and fuses about 600 million tons of hydrogen every second. Surface temperature ~5,500 °C; core ~15 million °C.
- Diameter1.39 million km
- Mass333,000 × Earth
- Age~4.6 billion yr
Encyclopedia
Meet the neighborhood
From a scorching rock that races the Sun to a deep-blue giant that takes 165 years to lap the sky — each world has a personality. Filter by type or jump straight to a profile.
Mercury
Terrestrial · 1st from the Sun
The smallest planet and the speedster of the system. Days last longer than years: one solar day is 176 Earth days. Almost no atmosphere, extreme temperature swings.
- Day length176 Earth days
- Year88 Earth days
- Moons0
- Mean temp167 °C
Venus
Terrestrial · 2nd from the Sun
Earth’s “evil twin” under a crushing CO₂ atmosphere and sulfuric acid clouds. Surface pressure is ~92× Earth’s; runaway greenhouse keeps it hotter than Mercury.
- Day length243 Earth days
- Year225 Earth days
- Moons0
- Mean temp464 °C
Earth
Terrestrial · 3rd from the Sun
The only known world with liquid water oceans, plate tectonics, and life. A protective magnetic field and oxygen-rich air make it uniquely habitable in the system.
- Day length24 hours
- Year365.25 days
- Moons1
- Mean temp15 °C
The Moon
Natural satellite of Earth
Stabilizes Earth’s tilt and drives the tides. Formed ~4.5 billion years ago, likely after a Mars-sized impact. Tidally locked — we always see the same face.
- Diameter3,474 km
- Distance~384,400 km
- Orbit27.3 days
- Gravity0.16 g
Mars
Terrestrial · 4th from the Sun
Home to Olympus Mons (tallest volcano) and Valles Marineris (a canyon system longer than North America). Thin CO₂ air; polar ice caps of water and dry ice.
- Day length24.6 hours
- Year687 Earth days
- Moons2
- Mean temp−65 °C
Jupiter
Gas giant · 5th from the Sun
More massive than all other planets combined. The Great Red Spot is a centuries-old storm larger than Earth. Over 90 moons, including volcanic Io and icy Europa.
- Day length9.9 hours
- Year11.9 Earth years
- Moons95+
- Diameter11 × Earth
Saturn
Gas giant · 6th from the Sun
Famous for its bright ice-and-rock ring system spanning ~282,000 km. Least dense major planet — it would float in a (very large) bathtub of water. Titan hosts lakes of methane.
- Day length10.7 hours
- Year29.5 Earth years
- Moons140+
- RingsExtensive
Uranus
Ice giant · 7th from the Sun
Spins on its side — axial tilt ~98°. Methane in the atmosphere gives the pale cyan color. Faint rings and 27 known moons; seasons last about 21 years each.
- Day length17.2 hours
- Year84 Earth years
- Moons27
- Tilt97.8°
Neptune
Ice giant · 8th from the Sun
Farthest major planet, found by math before it was seen. Supersonic winds and dark storms. Triton orbits backward and may be a captured Kuiper Belt object.
- Day length16.1 hours
- Year165 Earth years
- Moons16
- Windsup to 2,100 km/h
Pluto
Dwarf planet · Kuiper Belt
Reclassified in 2006, still a fan favorite. Nitrogen ice plains form a bright heart (Tombaugh Regio). Charon is so large the pair orbit a point outside Pluto.
- Day length6.4 Earth days
- Year248 Earth years
- Moons5
- Mean temp−229 °C
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