Black dwarf

A Black dwarf was a dark, compact star. The star in "the Ring" within the Ivax Nebula was a black dwarf. Less than 0.1 percent of the stars in the galaxy were black dwarfs.

Behind the scenes
In real life, a black dwarf is a white dwarf that had cooled down because of very old age. There aren't any of these stars yet, since white dwarfs take dozens of billions of years to radiate all its energy away as heat and lose all luminosity; i.e., it no longer gives off any significant heat or light, appearing black. This is after the star has been around for trillions of years&mdash;the process between changing from a white dwarf to a black dwarf takes billions of years on its own&mdash; and our Universe is not old enough for this to have occurred. The existence of such stellar remnants in the galaxy, in real world terms, is also impossible, as it is only about thirteen billion years old.