Neptune

Neptune, usually the eighth planet from the Sun, is a very cold place. Occasionally, Pluto crosses Neptune's orbit and becomes the eighth planet. Its bluish color comes from its atmosphere of methane gas.

Basic Facts

	Neptune	Earth
Position from the Sun	8 (usually)	3
Diameter	30,800 miles (49,500 km)	7,926 miles (12,753 km)
Moons	8	1
Rings	4	0
Average Distance from Sun	2,799,000,000 miles (4,504,000,000 km)	93,000,000 miles (149,000,000 km)
Your Weight on the Planet	Multiply your weight by 1.2	Multiply your weight by 1.0
Length of One Year	165 Earth years	1 Earth year
Length of One Day	17 hours and 6 minutes	24 hours
What’s in the Atmosphere?	Hydrogen, helium, methane	Nitrogen, oxygen
Temperature	-350ºF (-210ºC)	-128ºF to 136ºF (-89ºC to 58ºC)

Discovery

Neptune wasn't discovered the way all the other planets in our solar system were found. Astronomers didn't scan the sky with their powerful telescopes to find Neptune. They used math instead!

After the discovery of Uranus, astronomers were having trouble figuring out Uranus’ orbit. They realized that there must be another planet farther out than Uranus because this unknown planet’s gravitational pull slightly changes Uranus' orbit. They were right! French astronomer Leverrier and English astronomer John Couch Adams made the mathematical calculations of where Neptune should be in 1843, and German astronomer Johann Galle found it in 1846.

Missions to Neptune

Mission	Launch Date	Mission Accomplishments
Voyager 2 (USA)	August 20, 1977	Took thousands of pictures of Neptune, its rings, and its moons.

Interesting Facts About Neptune

	Neptune was actually the farthest planet from the Sun from February 7, 1979 until February 11, 1999 (the order was Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Pluto, and Neptune).
	Neptune will be the 8^th farthest planet from the Sun until the 23^rd century.
	Neptune’s Great Dark Spot is a huge storm the size of Earth.

[Return to Our Welcome Page]

We'd love to hear from you! Click one of the envelopes to send us your questions, comments, and suggestions.

Space: Today, Tomorrow, and Always

Novi Meadows Elementary School 2001

Unless otherwise noted, all images courtesy of NASA. Permission for use at http://www.nasa.gov/gallery/photo/guideline.html.

This site works best on a PC using Internet Explorer. There are some minor problems using Netscape, especially on Apples, but they can't be fixed. Sorry!