A Federation colony in the Aldebaran system, mentioned as the place where psychiatrist Elizabeth Dehner came aboard the Enterprise before its voyage to the galactic barrier.
The Aldebaran Colony is a Federation settlement mentioned in the Original Series pilot episode Where No Man Has Gone Before.
When Doctor Elizabeth Dehner is introduced on the bridge, she is described as having joined the ship at the Aldebaran Colony. Her assignment is to study how the crew react to emergency conditions, a task that takes a very different turn once she and Gary Mitchell are changed by the barrier at the edge of the galaxy.
The colony is never shown. The star's name recurs elsewhere in Star Trek, for instance in the Aldebaran whiskey that Guinan keeps aboard the Enterprise-D.