Neptune

Neptune is the outermost planet of the gas giants. It has an equatorial diameter of 49,500 kilometers (30,760 miles). If Neptune were hollow, it could contain nearly 60 Earths. Neptune orbits the Sun every 165 years. It has eight moons, six of which were found by Voyager. A day on Neptune is 16 hours and 6.7 minutes. Neptune was discovered on September 23, 1846 by Johann Gottfried Galle, of the Berlin Observatory, and Louis d'Arrest, an astronomy student, through mathematical predictions made by Urbain Jean Joseph Le Verrier.

The first two thirds of Neptune is composed of a mixture of molten rock, water, liquid ammonia and methane. The outer third is a mixture of heated gases comprised of hydrogen, helium, water and methane. Methane gives Neptune its blue cloud color.

This picture of Neptune was taken by Voyager 2 on August 20, 1989. One of the great cloud features, dubbed the Great Dark Spot by Voyager scientists, can be seen toward the center of the image. It is at a latitude of 22 degrees south and circuits Neptune every 18.3 hours. The bright clouds to the south and east of the Great Dark Spot constantly change their appearances in periods as short as four hours.

From www.solarviews.com

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