See below for July 2015 update
When I first made this graphic, it included two unexplored worlds: Ceres and Pluto, and 2015 seemed impossibly far away.
Now here we are, and only one remains. Of course, all these places have centuries of exploration ahead, but the era of unveiling major worlds in our solar system for the first time is reaching its twilight, right before our eyes. I almost don’t want it to end.
Updated July 2015
Now this chart is complete. (But the exploration of the solar system is not.)