Research by Kristy
Neptune is the outermost planet of the gasgiants. It has an equatorial diameter of 49,500
kilometers (30,760 miles). If Neptune were hollow, it could contain nearly60 Earths. Neptune
orbits the Sun every 165 years. It has eight moons, six of which were foundby Voyager. A day
on Neptune is 16 hours and 6.7 minutes. Neptune was discovered on September23, 1846 by
Johann Gottfried Galle, of the Berlin Observatory, and Louis d'Arrest, anastronomy 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.
Neptune is a dynamic planet with several large, dark spots reminiscent ofJupiter's hurricane-like
storms. The largest spot, known as the Great Dark Spot, is about the sizeof the earth and is
similar to the Great Red Spot on Jupiter. Voyager revealed a small, irregularlyshaped,
eastward-moving cloud scooting around Neptune every 16 hours or so. Thisscooter as it has
been dubbed could be a plume rising above a deeper cloud deck.
Long bright clouds, similar to cirrus clouds on Earth, were seen high inNeptune's atmosphere.
At low northern latitudes, Voyager captured images of cloud streaks castingtheir shadows on
cloud decks below.
The strongest winds on any planet were measured on Neptune. Most of thewinds there blow
westward, opposite to the rotation of the planet. Near the Great Dark Spot,winds blow up to
2,000 kilometers (1,200 miles) an hour.
Neptune has a set of four rings which are narrow and very faint. The ringsare made up of dust
particles thought to have been made by tiny meteorites smashing into Neptune'smoons. From
ground based telescopes the rings appear to be arcs but from Voyager 2 thearcs turned out to be
bright spots or clumps in the ring system. The exact cause of the brightclumps is unknown.
The magnetic field of Neptune, like that of Uranus, is highly tilted at47 degrees from the rotation
axis and offset at least 0.55 radii (about 13,500 kilometers or 8,500 miles)from the physical
center. Comparing the magnetic fields of the two planets, scientists thinkthe extreme orientation
may be characteristic of flows in the interior of the planet and not theresult of that planet's
sideways orientation or of any possible field reversals at either planet.