Solar System Superlatives

Solar System Superlatives

Largest planet: Jupiter (142,984 km [88,846 mi] diameter); all of the other planets in the solar system could fit inside Jupiter.

Largest moon: Jupiter’s moon Ganymede (5,268 km [3,273 mi] diameter).

Smallest planet: Mercury (4,879 km [3,032 mi] diameter).

Smallest moons: Saturn and Jupiter both have numerous satellites that are smaller than 10 km (6 mi) in diameter.

Planet closest to the Sun: Mercury (average distance from the Sun 58 million km [36 million mi]).

Planet farthest from the Sun: Neptune (average distance from the Sun 4.50 billion km [2.79 billion mi]); Pluto, demoted to the status of dwarf planet in 2006, was the farthest planet from the Sun for all but 20 years of its 248-year orbital period.

Planet with the most eccentric (least circular) orbit: Mercury (eccentricity of 0.206).

Moon with the most eccentric orbit: Neptune’s moon Nereid (eccentricity of 0.75).

Planet with the least eccentric orbit: Venus (eccentricity of 0.007).

Moon with the least eccentric orbit: Saturn’s moon Tethys (eccentricity of 0.0001).

Planet most tilted on its axis: Uranus (axial tilt of 98° from its orbital plane).

Planet with the most moons: Jupiter (at least 62).

Planets with the fewest moons: Mercury and Venus (none).

Planet with the longest day: Venus (1 day on Venus equals 243 Earth days).

Planet with the shortest day: Jupiter (1 day on Jupiter equals 9.9 Earth hours).

Planet with the longest year: Neptune (1 year on Neptune equals 165 Earth years).

Planet with the shortest year: Mercury (1 year on Mercury equals 88 Earth days).

Fastest orbiting planet: Mercury (47.9 km/sec [29.7 mi/sec] mean orbital velocity).

Slowest orbiting planet: Neptune (5.48 km/sec [3.40 mi/sec] mean orbital velocity).

Hottest planet: Venus (464 °C [867 °F] average temperature); although Mercury is closer to the Sun, Venus is hotter because Mercury has no atmosphere, whereas the atmosphere of Venus traps heat via a strong greenhouse effect.

Coldest planet: Neptune (−220 °C [−364 °F] average temperature).

Brightest visible star in the night sky: Sirius (apparent visual magnitude −1.46).

Brightest planet in the night sky: Venus (apparent visual magnitude −4.5 to −3.77).

Densest planet: Earth (density of 5,515 kg/m3).

Least dense planet: Saturn (density of 687 kg/m3); Saturn in theory would float in water.

Planet with strongest gravity: Jupiter (more than twice the gravitational force of Earth at an altitude at which one bar of atmospheric pressure is exerted).

Planet with weakest gravity: Mars (slightly more than one-third the gravitational force of Earth).

Planet with the largest mountain: Mars (Olympus Mons, an extinct volcano, stands some 21 km [13 mi] above the planet’s mean radius and 540 km [335 mi] across).

Planet with the deepest valley: Mars (Valles Marineris, a system of canyons, is some 4,000 km [2,500 mi] long and from about 2 to 9 km [1 to 5.6 mi] deep).

Largest known impact crater: Valhalla, a crater on Jupiter’s moon Callisto, has a bright central area that is about 600 km (370 mi) across, with concentric ridges extending about 1,500 km (900 mi) from the center. (The largest crater on Earth believed to be of impact origin is the Vredefort ring structure in South Africa, which is about 300 km [190 mi] across.)