Harper McKinley, age 15, of Denton, Tex., for his question:
WHO DISCOVERED THE PLANET NEPTUNE?
Credit for discovering the planet Neptune goes to two men: a young English astronomer and mathematician named John Adams and a young French mathematician named Urbain Leverrier. In 1845 and 1846 they both were looking for a new planet, unbeknown to each other.
Neptune is one of the two planets that cannot be seen without a telescope. Pluto is the other. Pluto is also the only planet that is farther from the sun than Neptune.
Neptune was discovered by means of mathematics. Astronomers had noticed that Uranus, which they thought was the most distant planet, was not always in the position they predicted for it. The force of gravity of some unknown planet seemed to be influencing Uranus.
Adams started his work to find an unknown planet in 1843 and came up with his very accurate findings in 1845. By the summer of 1846, Leverrier also had predicted the position of the unknown planet, Neptune.
Johann Galle, the director of the Urania Observatory in Berlin, Germany, received charts and details from both Leverrier and Adams. Then on Sept. 23, 1846, Galle and his assistant, Heinrich d'Asrrest, searched with a telescope the spot where the planet was predicted to be. They found it and they became the first to see it.
The planet was named for Neptune, the Roman sea god.
Neptune's diameter is about 30,760 miles, or almost four times the Earth's diameter. It is also about 17 times as massive, or heavy, as Earth.
Neptune goes around the sun once everey 165 years, compared to once a year for our planet. As the planet orbits the sun, it spins on its axis, an imaginary line through its center. The axis tilts about 30 degrees. Neptune spins around once in about 15 hours and 40 minutes.
Neptune is about 30 times as far from the sun as is the Earth.
The atmosphere surrounding Neptune is made up chiefly of hydrogen and methane gas, with some helium and ammonia. Astronomers think this atmosphere is about 2,000 miles thick.
Neptune is so far from the Earth that astronomers do not know much about its surface. They think the portion of Neptune visible from the Earth is the top of a thick layer of clouds. These clouds could be made of frozen ammonia, or combinations of crystals of ice and frozen methane and ammonia.
The tilt of Neptune's axis causes the sun to heat the planet's northern and southern halves unequally, resulting in seasons and temperature changes.
Temperatures on Neptune are much lower than those on our planet. The plant and animal life of the Earth could not live on Neptune because of the lack of oxygen and the low temperature. Astronomers do not know whether Neptune has any other form of life.
Two satellites or moons travel around Neptune. One, named Triton, is about 3,000 miles in diameter and about 200,000 miles from Neptune. It is the only large satellite in the solar system that travels in an east to west direction.