Has It Only Been A Year Since Neptune Was Discovered? The simple answer is yes and no. Yes because 165 years ago, on September 23rd 1846, the planet Neptune was discovered. And
it takes 165 Earth years for Neptune to make one revolution around the Sun -- a Neptunian year. So no it has not quite been a year, if we start from
the day of discovery. However the heliocentric coordinates for the planet are the same, or about as close as they can be, on July 12th as they were on
September 23rd 1846. So in that sense the planet Neptune, on July 12th, will have completed one revolution since its discovery.
I used the Horizons ephemeride tool at NASA's Solar System Dynamics
web site to calculate the coordinates for Neptune on its discovery date and also on July 12th of this year. I used the same time and as you can see
all of the numbers either match or are very close
