Neptune

Dark, cold, and whipped by supersonic winds, ice giant Neptune is the eighth and most distant planet in our solar system.More than 30 times as far from the Sun as Earth, Neptune is the only planet in our solar system not visible to the naked eye and the first predicted by mathematics before its discovery. In 2011 Neptune completed its first 165-year orbit since its discovery in 1846.

Neptune does not have a solid surface. Its atmosphere (made up mostly of hydrogen, helium, and methane) extends to great depths, gradually merging into water and other melted ices over a heavier, solid core with about the same mass as Earth.

The core of Neptune is likely composed of iron, nickel and silicates, with an interior model giving a mass about 1.2 times that of Earth. The pressure at the centre is 7 Mbar (700 GPa), about twice as high as that at the centre of Earth, and the temperature may be 5,400 K.

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.