I came across the article talking about how Neptune is now just about under a year from completing its first full orbit since it was discovered by humans, that is 164 years to go around the sun once.  Pretty amazing amount of time, and learning that it takes the outer planets that long to travel around the sun really puts into perspective as to how huge just our own solar system is.  I know the solar system is huge but just did not quite understand how big, since when you hear a planet is so many billion miles or kilometers away from Earth it is sometimes hard to get a true sense of scale.  That is where the time it takes to travel around the sun really helps to put it into perspective.

As Neptune is located so far away from the sun (approximately 4.5 billion kilometers, 30 Astronomical Units (AU), or 30-times the sun-Earth distance), it takes over 164 Earth years to complete one full orbit around our star.

As the first direct observation of the blue-green gas giant was made on Sept. 23, 1846, Neptune will arrive back in approximately the same spot as where it was first spotted on July 12, 2011.

via When Will Neptune Complete Its First Orbit Since Discovery? : Discovery News.

For comparison sake it takes Uranus 84 years to make a complete circuit, first discovered in 1781 and first one completed 1865.  For Pluto it is even longer than Neptune taking 248 years for each rotation, first discovered in 1930, won’t make a complete rotation until 2178.