Technical Entry – Names of Stars

Stars, in the way we are naming them, are named using the Bayer classification system, named after the German astronomer Johann Bayer. He divided the sky into wedges defines by the constellation in that wedge, and named the stars by brightness. Bayer assigned a lower-case Greek letter (alpha (α), beta (β), gamma (γ), etc.) or a Latin letter (A, b, c, etc.) to each star he catalogued, combined with the Latin name of the star’s parent constellation in genitive (possessive) form. Alpha Centauri, for example, means the brightest star in the Centaurus constellation wedge.

Bayer used Greek letters for the brighter stars, but the Greek alphabet has only twenty-four letters, while a single constellation wedge may contain fifty or more stars visible to the naked eye. When the Greek letters ran out, Bayer continued with Latin letters: upper case A, followed by lower case b through z (omitting j and v, but o was included), for a total of another 24 letters.

Bayer did not label “permanent” stars with uppercase letters (except for A, which he used instead of a to avoid confusion with α). However, a number of stars in southern constellations have upper-case letter designations, like B Centauri and G Scorpii. These letters were assigned by later astronomers following Bayer’s use of Greek letters, but this was insufficient for many constellations. He used first the lowercase letters, starting with a, and if needed the uppercase letters, starting with A, thus deviating somewhat from Bayer’s practice. Lacaille used the Latin alphabet three times over in the large constellation Argo Navis, once for each of the three areas that are now the constellations of Carina, Puppis, and Vela. That was still insufficient for the number of stars, so he also used uppercase Latin letters such as N Velorum and Q Puppis. Lacaille assigned uppercase letters between R and Z in several constellations, but these have either been dropped to allow the assignment of those letters to variable stars or have actually turned out to be variable. Most of these letters have had names assigned to them, like hurricane names.

The Noctis sector, and therefore most of this story, is in the Eridanus constellation wedge, so most of the stars are designated (something) Eridani.