Neptune vs. Pluto

What's the Difference?

Neptune and Pluto are both outer planets in our solar system, but they have distinct differences. Neptune is the eighth planet from the sun and is known for its vibrant blue color and strong winds, while Pluto is the ninth planet (formerly considered the ninth planet before being reclassified as a dwarf planet) and is much smaller and colder. Neptune has a thick atmosphere made up of hydrogen, helium, and methane, while Pluto has a thin atmosphere composed of nitrogen, methane, and carbon monoxide. Despite their differences, both planets are fascinating objects of study for astronomers and continue to reveal new insights about the outer reaches of our solar system.


Photo by NASA on Unsplash
Diameter49,244 km2,377 km
Distance from Sun4.5 billion km5.9 billion km
Moons14 known moons5 known moons
AtmosphereMainly hydrogen and heliumThin atmosphere of nitrogen, methane, and carbon monoxide
DiscoveryDiscovered in 1846Discovered in 1930
Photo by NASA on Unsplash

Further Detail

Physical Characteristics

Neptune and Pluto are both considered ice giants in our solar system, but they have distinct physical characteristics that set them apart. Neptune is the eighth and farthest planet from the sun, while Pluto was reclassified as a dwarf planet in 2006. Neptune is much larger than Pluto, with a diameter of about 49,244 kilometers compared to Pluto's 2,377 kilometers. Additionally, Neptune has a blue hue due to the presence of methane in its atmosphere, while Pluto appears reddish-brown.


The atmospheres of Neptune and Pluto also differ significantly. Neptune's atmosphere is composed mainly of hydrogen, helium, and methane, with traces of other gases. It has a dynamic weather system with high-speed winds and large storms, such as the famous Great Dark Spot. In contrast, Pluto has a thin atmosphere consisting of nitrogen, methane, and carbon monoxide. Its atmosphere is much colder and less active compared to Neptune's.


Both Neptune and Pluto have moons orbiting around them, but the number and characteristics of their moons vary. Neptune has 14 known moons, the largest of which is Triton, a captured Kuiper Belt object. Triton is unique among large moons in the solar system because it orbits in the opposite direction of Neptune's rotation. In contrast, Pluto has five known moons, with the largest being Charon. Charon is so large compared to Pluto that some scientists consider the two bodies to be a binary system.

Orbit and Distance from the Sun

Neptune and Pluto have different orbits and distances from the sun, which contribute to their unique characteristics. Neptune orbits the sun at an average distance of about 4.5 billion kilometers, taking approximately 165 Earth years to complete one orbit. Pluto, on the other hand, has a highly elliptical orbit that takes it as close as 4.4 billion kilometers and as far as 7.4 billion kilometers from the sun. This eccentric orbit is one of the reasons why Pluto was reclassified as a dwarf planet.

Discovery and Exploration

Neptune was discovered in 1846 by Urbain Le Verrier and Johann Galle through mathematical predictions based on perturbations in the orbit of Uranus. It was the first planet to be discovered through mathematical calculations rather than direct observation. In contrast, Pluto was discovered in 1930 by Clyde Tombaugh through a systematic search of the night sky. Both Neptune and Pluto have been visited by spacecraft from Earth, with Voyager 2 flying by Neptune in 1989 and New Horizons conducting a flyby of Pluto in 2015.

Composition and Surface Features

The composition and surface features of Neptune and Pluto also differ significantly. Neptune is primarily composed of rock and ice, with a dense core of rock and metal surrounded by a mantle of water, ammonia, and methane ice. Its surface features include dark spots, bright clouds, and a faint ring system. In contrast, Pluto is composed of rock and ice, with a thin atmosphere that freezes and falls to the surface as snow. Its surface features include mountains, plains, and a large heart-shaped region known as Tombaugh Regio.


In conclusion, Neptune and Pluto are two fascinating objects in our solar system with unique attributes that make them stand out. Neptune is a giant planet with a dynamic atmosphere, numerous moons, and a blue hue, while Pluto is a dwarf planet with a cold, thin atmosphere, a binary relationship with its largest moon, and a heart-shaped region on its surface. Despite their differences, both Neptune and Pluto continue to intrigue scientists and space enthusiasts alike with their mysteries waiting to be uncovered.

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