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The Gas (and Ice) Giant Neptune

Neptune photographed by Voyage. Image credit: NASA/JPL

Neptune photographed by Voyage. Image credit: NASA/JPL

Neptune is one of the four gas giants in our Solar System, as well as being one of the four outer planets. Actually, since Pluto was demoted to a dwarf planet, Neptune is the eighth and final planet in our Solar System. As a gas giant, Neptune has no solid surface, so even if a spaceship could reach it, it could not land because it would simply keep sinking into the planet. Neptune is the fourth smallest planet in the Solar System (judging by diameter), but it actually has more mass than Uranus does. The planet also has rings, although they are not as spectacular as Saturn’s are. Neptune’s rings are actually faint and somewhat hard to see. Scientists were not actually positive that the planet had rings until a probe passed by and was able to confirm it.

Neptune cannot be seen with the naked eye and was therefore not discovered until 1846. There is some debate as to who actually discovered the planet because more than one person claimed credit for it. Most modern scientists agree that Urbain Le Verrier actually deserves most of the credit for the discovery. The other astronomer, John Couch Adams, was quite a bit off in his calculations. Galileo had actually seen the planet before, but he believed it to be a fixed star rather than a planet. There was quite a battle over the naming of Neptune because the two astronomers were from different countries and their respective countries wanted it named after one of the astronomers. Eventually, a name inspired by mythology was chosen instead.

Although Neptune is a gas giant, it is actually in a subclass of gas giants known as ice giants. It has a higher percentage of “ices” in its atmosphere; these ices include methane and ammonia. The large amounts of methane in the atmosphere of the planet are what cause its blue color.

The planet has 13 moons, the largest of which is Triton. The moons were named after lesser sea gods because Neptune is the Roman god of the sea. One interesting fact about Neptune is that sometimes Pluto is closer to the Sun than Neptune is. This is due to Pluto’s highly irregular orbit. Neptune is also known for the terrific storms that ravage the planet. In fact, some of these storms were named, such as the Great Dark Spot, which was seen in 1989, or the Small Dark Spot, also seen in 1989.

Characteristics of Neptune

Position and Movement of Neptune

Neptune’s Moon and Rings

History of Neptune

Neptune’s Surface and Structure


Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

Comments on this entry are closed.

  • maria January 5, 2009, 5:50 PM

    hey ppls!!!!

  • maria January 5, 2009, 5:51 PM

    hello ma name is maria wats urs im soo beautful nd i luv these planets that the lord created the universe