Valacirca "Sickle of the Valar", was one of the constellations set in the heavens by Varda to enlighten the awakening of the elves and gathered by Varda from among the ancient stars (Silmarillion, Chap. 3; cf. MR 71, 160). Other constellations were Wilwarin, Telumendil, Soronúmë, Anarríma and Menelmacar (or Telumehtar).
Valacirca is by far the most important constellation in the heavens of Arda. It is also the first to appear in the mythology that J.R.R. Tolkien begun to develop in the 1910's.
Valacirca can be identified with Ursus Major, the Great Bear, or, more precisely, the Big Dipper (Plough in Great Britain) with its seven stars, often referred to in the writings of Tolkien.
Another name-form: Valakirka