Hansen's Planet was an inhabited planet. This was the homeworld for a species of anthropoids. Prior to stardate 2821, this planet had previously been explored by Federation anthropologists.
While looking for survivors of the downed Galileo on Taurus II, Lieutenant Kelowitz's landing party was attacked by a species of anthropoids. When back aboard the USS Enterprise, the lieutenant stated that these anthropoids were similar to those found on Hansen's Planet. (TOS: "The Galileo Seven")
The location of Hansen's Planet was marked on the star chart Data and Picard were studying in the stellar cartography department on USS Enterprise-D in 2371. (Star Trek Generations, display graphic)