How big is Neptune? How long is its day? How far from the Sun is it? Find out all this and more.

Neptune Facts

Neptune is the eighth planet from the Sun, and now considered the furthest planet from the Sun since Pluto was demoted from its planetary status. Neptune and Pluto sometimes change position in orbit, but in general, Neptune is closer to the Sun that Pluto.

In distance, Neptune lies about 30 AU, or astronomical units, from the Sun. One AU equals the distance between Earth and the Sun.

Neptune is a gas giant, but it is the smallest of the four gas giant planets. It is 49,500 kilometers in diameter, making it about four times larger than Earth and three times smaller than Jupiter.

Neptune was named after the Roman God of the Sea. Its bluish hue may give one the impression of water, but in fact it is just Neptune's thick atmosphere. In order to see Neptune, you have to use binoculars or a telescope. It should appear like a tiny circle, instead of pointlike, as stars do. You may even notice the blue color.

Because Neptune travels very slowly around the Sun, one Neptune year equals 165 Earth years. However, Neptune spins more quickly than Earth, with its day lasting just over 16 hours.

Neptune was discovered on September 23, 1846, by Johann Gottfried Galle. It is unusual in that its existence was known before it was discovered. Mathematicians realized after Uranus's discovery that another large planet must exist beyond it.

The moon Triton was discovered with Neptune. It is Neptune's largest moon and the only large moon in the solar system to orbit opposite its planet's rotation. It has a south polar cap and geysers of dark nitrogen. It may have been a dwarf planet like Pluto before being captured.

Neptune's other large moon, Nereid, was discovered in 1949. It may have been an asteroid or other captured object because its orbit is the most highly eccentric orbit of any planet or satellite in the solar system.

Most of what we know about Neptune comes from Voyager 2. It found that the planet has at least eight moons and a thin ring. The ring is made up of four dusty rings and brighter ring clumps. The Great Dark Spot is a hurricane-like storm on the planet that has been raging at least 400 years. Voyager 2 discovered a smaller bright cloud that raced around the atmosphere. It was named Scooter. Neptune has the fastest measured winds in the solar system at 2000 kilometers an hour.

For more on the solar system, follow the links below.

Sun Mercury Venus Earth Mars Jupiter Saturn Uranus