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Neptune orbits the Sun at an average distance of 4.5 billion kilometers, so it takes a much longer journey to travel around the Sun. While a year on Earth is approximately 365.25 days, a year on Neptune is 60,190 days or 164.79 years.
Here’s what makes this kind of interesting. Neptune was first discovered in 1846. At the time that this article is being written in 2008, we’ve only known about the planet for 162 years. In other words, Neptune hasn’t even completed a single orbit around the Sun since we discovered it.
That first year will occur in 2010.
Just like Earth, Neptune experiences seasons as it travels around the Sun. It has an axial tilt of 28.3 degrees, which is very similar to the Earth’s tilt. For half the year, one pole is tilted towards the Sun, and then the situation flips, and the other pole is shifted towards the Sun. The seasonal change on Neptune has an interesting feature. The south pole on Neptune is currently the warmest spot on Neptune. As it moves through its seasons, this warm spot will shift to Neptune’s north pole as it faces the Sun.
We have recorded an entire episode of Astronomy Cast just about Neptune. You can listen to it here, Episode 63: Neptune.