Soror

Soror was the slightly smaller of Trenzalore's two moons and was silver in color. Since the planet only got minutes of daylight, Soror helped to create lunar-synthesis allowing plant and animal life to grow. (PROSE: Strangers in the Outland)

In an alternate timeline, Soror was destroyed. (TV: The Name of the Doctor)

Behind the scenes
The name "Soror" is drawn from the Latin word for sister.