What is the defining point in the death of a star?
The smaller the starting point of a star is, the longer it will live.
For example, a white dwarf is not yet a dead star because it still shines with a cool, white light. At some point, some of its energy will gone. It becomes a dead star.
The length of time it takes a medium-sized star to become a white dwarf depends on the mass of the star when it first formed. For a medium-sized star like our sun, it will take about 10 billion years to pass from formation to its death.
A smaller medium-sized star may take as long as 100 billion years .
A large medium-sized star may die within only a few billion years .
It is because,"the smaller the starting point of a star is, the longer it will live."