Neptune is, as of 2006, the last full planet in our solar system, and is the last of the gas giants that are filled to the brim with hydrogen and helium in their atmospheres. Like neighboring Uranus, Neptune’s blue color comes from methane. However, Neptune’s blue is brighter than the blue on Uranus, leaving scientists to wonder what causes the more vivid coloring.

 

The planet completes an orbit around the sun every 165 Earth years with a day on the planet lasting a little over 16 Earth hours. Due to its distance from Earth (which changes over time given the planet’s odd orbital patterns), Neptune is not visible with the naked eye, and in fact the planet’s existence was hypothesized through math due to changes in Uranus’ orbit.

 

Like Uranus, Neptune has not been the focus of much scientific research. Voyager 2, the first spacecraft to visit Uranus, was also the first and only spacecraft to visit Neptune, passing over the planet’s north pole in 1989. In 1998, scientists discovered that the planet had rings and ring arcs around it.

 

(Photo: NASA)