The eighth planet from the Sun in the solar system. Neptune orbits the Sun at an average distance of 30 AU. The planet has a mass 17.1 times the mass of Earth and a radius 3.9 times the radius of Earth. Neptune is a gas planet made of hydrogen, helium, and methane and has no solid surface. It has a small ring system and 14 known moons, the largest of which is Triton.


Neptune's Triton Triton is a world like no other. Geysers of gas...
Realm of the Giants The region beyond the asteroid belt is the realm...
Neptune Neptune might be called the mathematicians'...

Radio Programs

Neptune at Opposition II Cranking up the winds on a distant planet Monday, August 31, 2015
Neptune at Opposition Neptune in the sky with diamonds Sunday, August 30, 2015
Neptune at Opposition Lining up a blue-green giant Wednesday, August 27, 2014
Voyager 2 at Neptune A first glance at a giant world Monday, August 25, 2014
Neptune at Opposition Probing deep into a planet’s atmosphere Monday, August 26, 2013
Missed Opportunity Missing a “stellar” opportunity Monday, January 28, 2013
Johann Galle Taking note of a new planet Saturday, June 9, 2012
Triton A frigid moon like no other Tuesday, August 23, 2011
Neptune at Opposition Pulverizing a Neptunian moon Monday, August 22, 2011
Urbain Leverrier A "calculated" planetary discovery Friday, March 11, 2011
Neptune’s First Orbit A planet returns to its beginnings Sunday, November 7, 2010

Featured Images

Diagram shows Neptune and some of its moons, including one discovered in 2013
Second-Look Moon Monday, July 22, 2013
Voyager 2 view of the Adams Ring at Neptune
Pulverized Moon Monday, August 22, 2011


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