Star of Eärendil
The shining light of the Silmaril rescued from Angband by Lúthien and Beren, and carried into the skies by their descendant Eärendil aboard his vessel Vingilot. As it first rose in the West, it was recognised by Maedhros as the Jewel of his father that he had sought for so long, now placed out of his reach beyond the confines of the World.
It was Eärendil and the light of his Star that led the Edain to Númenor in the early Second Age, and at that time the light of the Star was so brilliant that it hid all the other stars in the sky. From its guiding light came one of the Númenóreans' names for their land, Elenna, meaning 'Starwards'.
The light of Eärendil's Star played a crucial role much later in history, too: it was light from this Star that was trapped in Frodo's Star-glass, his gift from Galadriel, which helped him survive his journey into Mordor. Even today, the Star still shines - the story of Eärendil and his Silmaril was the Elvish account of the 'star' we know today as the planet Venus.