Jack of Harts

Gamma Hydrae killed most of the first colonists. Radiation poisoning destroyed their cellular linings and caused them to deteriorate until they died. In a time when old age was becoming a thing that people used to die of, the people in that system died of it in a matter of months. It was an ugly and very permanent way to die. One of the colonists turned out to be Ageless though, and her body fought the radiation. That gave the medical types something to work with.