Neptune

        Little was known about Neptune ,which was discovered in 1846, until

the Voyager 2 encounter in 1989. It has a similar composition to Uranus and

is close in mass to Uranus. Its thick atmosphere made of hydrogen, helium,

and some methane and ammonia, gives it a bluish color.

DISCOVERY

        On August 25, 1989, the voyager discovered Neptune, but only after

traveling 12 years at an average velocity of 19 kilometers a second (about 42

miles an hour). The Voyager 2 observed Neptune almost continuously from

June to October 1989. This discovery though, gives us just about all the info

about Neptune.

BACKGROUND

        Astronomers have studied Neptune since September 23, 1846, when

Johann Gottfried Galle, of the Berlin Observatory, and Louis d'Arrest, an

astronomy student, discovered the eighth planet on the basis of mathmatical

predictions by Urbain Jean Joseph Le Verrier. Scarcely after Galle and

d'Arrest first saw Neptune, British astonomer William Lassell spotted a moon

orbiting the planet and named it Triton (Which is explained in greater detail

later in the report).

        In 1949 astonomer Gerard Kuiper discovered Nereid, the second

largest moon of Neptune. Nereid is only about 340 kilometers (210 miles) in

diameter and is so far from Neptune that it requires 360 days to make one

orbit.

        In 1981, a star would pass behind Neptune so that observers could

measure the starlight and how it changed as it passed through the upper layer

of Neptune's atmosphere. But the star's light flashed on and off before

Neptune passed in front of it. Astronomers concluded that some material

orbits Neptune, and was responsible for occasional blockage of the star's

light.

NEPTUNE FACTS AND FIGURES

        Neptune is the eighth planet from the sun and the fourth largest by

diameter. Neptune is smaller in diameter but larger in mass than Uranus.