J.R.R. Tolkien> The Lord of the Rings / The Silmarillion

The Sickle of the Valar

The Wain, which corresponds to today's Ursa Major, was one of the two most important constellations in the sky of Arda. It was set in the sky three ages before the First Age as a warning to Melkor and all who served him.

Only from the map did Bilbo know that away up there, where the stars of the Wain were already twinkling, the Running River came down into the lake from Dale and with the Forest River filled with deep waters what must once have been a great deep rocky valley.

-J.R.R. Tolkien
The Hobbit