Welcome To The Universe

An Infinite Guide To Everything Outside Our World

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The Blue Giant

Neptune is the eight planet from the sun and is named after the Roman god of the sea. It is also a gas giant. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 Earth masses and not as dense. Neptune was the first planet found by mathematical prediction rather than by empirical observation(scanning the sky with a telescope). Unexpected changes in the orbit of Uranus led astronomers to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently found within a degree of its predicted position, and its largest moon, Triton, was discovered shortly thereafter, though none of the planet's remaining 12 moons was located telescopically until the 20th century. Neptune has been visited by only one spacecraft, Voyager 2 on Aug 25 1989. It was the last stop in 1989 for the Voyager 2 spacecraft on its grand tour of the solar system.

Neptune has eight known moons: Triton, Thalassa, Naiad, Despina, Galatea, Larissa, Proteus and Nereid. Neptune has been particularly challenging to study from the ground because its disk is small and badly blurred by the Earth's atmosphere at that distance. In spite of this, ground-based astronomers had learned a great deal about this planet since its position was first predicted by Adams and Leverrier in 1845. However, our most detailed information about Neptune has come from the Voyager 2 flyby in 1989.


Neptune's Orbit

Neptune has a regular orbit, just 0.01 from the circular. Only 101 million kilometers separate its points farthest and nearest from the sun, its perihelion and aphelion, respectively. This seems like a large distance, which it is�for instance, the difference is greater than Mercury�s aphelion. But considering the four-billion-kilometer distances involved, the difference is almost inconsequential. A day on Neptune is two-thirds that of Earth, but its year is almost 165 times longer. Given the short rotational period and the long orbital period, it should be no surprise that there are almost 89,700 Neptunian days in a Neptunian year! Neptune�s orbit also figures into its discovery. It passes close enough to Uranus to significantly alter that planet�s orbit, which lead mathematicians in England and France to interdependently hypothesize its existence.

Facts about Neptune

  • Neptune cannot be viewed with the naked eye in the sky.

  • Neptune orbits the sun once every 165 years.

  • We have visited Neptune once with the Voyager 2 probe in 1989.

  • Neptune is the Roman god of the sea.

  • Neptune will be closer to the Sun than Pluto for 220 years and then reverse positions for 20 years.

  • Neptune is more than 2 billion miles from the Sun.

  • The largest storm on Neptune is known as the Great Dark Spot and would nearly cover the Earth if on our planet.


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