Introduction

Neptune is a large planet on our solar system, seventeen times more massive than Earth and far more blue. It is the eighth planet out from our sun, and five planets further out than Earth, or 2.7 billion miles (4.3 billion kilometers) away. Neptune, at about 2.8 billions miles (4.5 billion kilometers) from the sun, is the most remote of the large planets. It lies a billion miles beyond Uranus and almost that far from the last planet in the solar system, Pluto. Althought Neptune's day is shorter than ours (just over sixteen hours) it orbit the sun only once every 165 Earth years. Since it is the color of water, Neptune was named for the Roman god of the sea. But Neptune's blue-green color is not that of a sea. It is due to methane gas. Neptune wears a cold (-352 degrees Fahrenheit, or -213 degrees celsius) outer layer of hydrogen, helium. Within that lies a layer of ionized (electrically charged) water, ammonia, and methane ice, and deeper yet is a rocky, iron core.

What are conditions like on Neptune?

Neptune is subject to the fiercest winds in the solar system. Its layer of blue surface clouds whip around with the wind while an upper layer, wispy white clouds of methane crystals, rotate with the planet. Three storm systems are evident on Neptune's surface. The most prominent is a dark blue area called the Great Dark Spot, which is about the size of the Earth. Another storm, about the size of our moon, is called the Small Dark Spot. Then there is Scooter, a small, fast-moving white storm system that seems to chase the other storms around the planet.

Who discovered the planet Neptune?

Since William Herschel's discovery of Uranus in 1781, astronomers had wondered if that planet's fluctuating orbit was caused by the pressure of another planet's gravitational field. In 1843, the year that he graduated first in his class in mathematics from Cambridge University, John Couch Adams, a self-taught astronomer, completed his calculations of the location of the unknown planet. In 1845, Adams presented his findings to England's highest authority on such matters, George Airy, the Astronomer Royal. Airy paid little attention to Adam's work. Some authorities think that Airy ignored Adams's discovery because he was working on his own theory to explain Uranus's orbit. One year later, Airy was forced to reconsider. A French astronomer named Urbain Jean Leverrier (1811-1877) announced that he had determined the position of the new planet. Leverrier's calculations placed the planet at almost the exact location as had Adams. Scientists at the Cambridge Observatory and the Berlin Observatory confirmed the findings of both men.

What causes the magnetic field on Neptune?
The magnetic field that has been measured on Neptune is tilted from its axis at a 48 degree angle and just misses the center of the planet by thousands of miles. Given the planet's frigid exterior, it is surprising that this field is created by 4,000-degree-Fahrenheit (2,200-degree-Celsius) water beneath its surface, water so hot and under so much pressure that it generates an electrical field.

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