Designation Systems

The system introduced by Johann Bayer in his 1603 atlas Uranometria, labelling the bright stars of each constellation with a Greek letter followed by the Latin genitive of the constellation's name — so α Orionis is Betelgeuse, even though Rigel (β Orionis) is usually the brighter of the two, a reminder that the ordering is only approximate. Roughly in order of brightness, Bayer letters remain the most familiar designations for naked-eye stars.

A numbering scheme drawn from John Flamsteed's star catalogue, published posthumously in 1725, that labels the stars of each constellation with a number in order of increasing right ascension — so 61 Cygni is the sixty-first Flamsteed star of Cygnus. Flamsteed numbers name many stars that have no Bayer letter.

The scheme for naming variable stars, formalised in the General Catalogue of Variable Stars. Within each constellation the first variables take the letters R through Z, then two-letter combinations RR through ZZ and AA through QZ, and thereafter V335, V336, and so on — a system that grew from a handful of early discoveries into a labelling scheme for tens of thousands of variables.