Dead star

A dead star, occasionally called a dead sun, was a type of astronomical object.

A strange example of such a star was found to be orbited by an ancient insectoid ship 2269. 

In the Mirror universe, the Tholians detonated a tricobalt warhead inside the gravity well of a dead star, thus creating an interphasic rift forming a doorway into another universe. 

In 2370, Professor Gideon Seyetik attempted to re-ignite a dead star called Epsilon 119 using protomatter. The theory was that it would cause a cascade effect transforming the star's carbon and oxygen into elemental hydrogen. He succeeded but lost his life in the attempt. 

The antimatter universe contained dead stars too, for example Amphion, counterpart of Beta Niobe. In 2270, it unnexpectedly went nova, and a gateway to the regular universe opened up, apparently by Beta Niobe going nova at the same time.