It is one year since Neptune was discovered, so join me in wishing the solar system's most distant planet a happy first birthday!!! When I say "one year" I mean one year on Neptune. This is because Neptune has completed its first trip around the Sun since it was discovered in October 1846.
Because Neptune is so far away from the Sun, it takes the planet almost 165 years to orbit the Sun. This means that a year on Neptune is 165 years long. On Earth, a year is 365 days, this being the length of time it takes for Earth to complete an orbit (it's actually 365 days and a quarter - an extra day is added every four years to catch up). Tuesday 12th July 2011 marks the date that Neptune will be in the same place in its orbit around the Sun as it was when it was first found all that time ago.
Despite us knowing about Neptune for 165 years, we still know very little about the planet. We know it is likely to be made up of mostly frozen gasses, and that it is a stormy world with strong winds, but there is more that we don't know about Neptune than we do know. It has only been visited once, and that was by Voyager 2 which reached it in 1989. There are no plans to visit it again in the near future. Maybe things will be different by the time it completes its second orbit.