Neptune

Neptune

Neptune—the eighth and most distant major planet orbiting our Sun—is dark, cold and whipped by supersonic winds. It was the first planet located through mathematical calculations.

10 Need-to-Know Things About Neptune

  • GIANT

    Neptune is about four times wider than Earth. If Earth were a large apple, Neptune would be the size of a basketball.

  • EIGHTH WANDERER

    Neptune orbits our Sun, a star, and is the eighth planet from the Sun at a distance of about 2.8 billion miles (4.5 billion kilometers).

  • SHORT DAY, LONG YEAR

    Neptune takes about 16 hours to rotate once (a Neptunian day), and about 165 Earth years to orbit the sun (a Neptunian year).

  • ICE GIANT

    Neptune is an ice giant. Most of its mass is a hot, dense fluid of "icy" materials – water, methane and ammonia – above a small rocky core.

  • GASSY

    Neptune's atmosphere is made up mostly of molecular hydrogen, atomic helium and methane.

  • MOONS

    Neptune has 14 known moons which are named after sea gods and nymphs in Greek mythology.

  • FAINT RINGS

    Neptune has at least five main rings and four more ring arcs, which are clumps of dust and debris likely formed by the gravity of a nearby moon.

  • ONE VOYAGE THERE

    Voyager 2 is the only spacecraft to have visited Neptune. No spacecraft has orbited this distant planet to study it at length and up close.

  • LIFELESS

    Neptune cannot support life as we know it.

  • ONE COOL FACT

    Because of dwarf planet Pluto’s elliptical orbit, Pluto is sometimes closer to the Sun (and us) than Neptune is.

Exploration

The human on the moon Galileo recorded Neptune as a fixed star during observations with his small telescope in 1612 and 1613. More than 200 years later, the ice giant Neptune became the first planet located through mathematical predictions rather than through regular observations of the sky. Because Uranus didn't travel exactly as astronomers expected it to, French mathematician Urbain Joseph Le Verrier proposed the position and mass of a then-unknown planet that could cause the observed changes to Uranus' orbit. Le Verrier sent his predictions to Johann Gottfried Galle at the Berlin Observatory, who found Neptune on his first night of searching in 1846. Seventeen days later, Neptune's largest moon Triton was discovered as well. More than 140 years later, in 1989, NASA's Voyager 2 became the first-and only-spacecraft to study Neptune up close. Voyager returned a wealth of information about Neptune and its moons-and confirmed evidence the giant world had faint rings like the other gas planets. Scientists also use the Hubble Space Telescope and powerful ground-based telescopes to gather more information about this distant planet.