Pleiades

(astronomy) An open cluster of a few hundred stars in the constellation Taurus; six of the stars are easily visible to the naked eye.

A beautiful group of stars resembling a little dipper, in the constellation of Taurus, known since earliest records. The Pleiades is a typical open cluster (see illustration). Its distance is 410 light-years (2.4 × 10¹⁵ mi or 3.9 × 10¹⁵ km), its linear diameter about 15 light-years (9 × 10¹³ mi or 1.4 × 10¹⁴ km). The cluster is permeated with diffuse nebulosity. Though early accounts refer to the Pleiades in terms of seven stars, only six are now conspicuous to the unaided eye, which raises a theory that one, the lost Pleiad, has faded. The observation of flare stars and x-ray emission has increased interest in this cluster. See also Constellation; Star clusters.

The Pleiades. (Lick Observatory photograph)