Six months before the star supernovaed, the Federation had set up a research station on this planet to make close-up studies of the star. When the star reached its critical point, the USS Enterprise arrived to pick up the team.
They found the team was missing, and were soon abducted by a race known as the Vians. They found that the team had been killed by the Vians in an attempt to find out if a race of mutes were worthy of survival. (TOS: "The Empath")