§ Of the Sun and Moon and the Hiding of Valinor The Silmarillion

The maiden whom the Valar chose from among the Maiar to guide the vessel of the Sun was named Arien, and he that steered the island of the Moon was Tilion. In the days of the Trees Arien had tended the golden flowers in the gardens of Vána, and watered them with the bright dews of Laurelin; but Tilion was a hunter of the company of Oromë, and he had a silver bow. He was a lover of silver, and when he would rest he forsook the woods of Oromë, and going into Lórien he lay hi dream by the pools of Estë, in Telperion's flickering beams; and he begged to be given the task of tending for ever the last Flower of Silver. Arien the maiden was mightier than he, and she was chosen because she had not feared the heats of Laurelin, and was unhurt by them, being from the beginning a spirit of fire, whom Melkor had not deceived nor drawn to his service. Too bright were the eyes of Arien for even the Eldar to look on, and leaving Valinor she forsook the form and raiment which like the Valar she had worn there, and she was as a naked flame, terrible in the fullness of her splendour.