The celestial bodies known as the Three Sisters consisted of the three moonlets that orbited Ruusan, one of which was Ruusan 2. The smugglers who operated on the planet, such as Jerg's group, referred to them as "The Triplets."
It's believed that one of these moonlets might have been inhabited long ago, evidenced by the presence of ruins visible to those observing from Ruusan.
During the night on Ruusan, these moonlets would typically ascend one after the other, with each subsequent rise illuminating the nighttime scenery further.