Names of the Stars
At least beginners aren't alone in their confusion. The First Dictionary of the Nomenclature of Celestial Objects, 1983, described well over 1,000 different naming systems then in use, mostly for faint objects studied by professionals. Its editors despaired of the list ever being made orderly, reasonable, or complete. Celestial nomenclature is too freakish for that, too full of schemes from times long past.
Fortunately, a well-rounded amateur needs to know only a tiny fraction of these naming systems. In this article we'll cover those most often encountered for stars, with their meanings and histories. Another article covers the nomenclature of deep-sky objects.
Where the Heck is Zujj Al Nushshabah?
Since ancient times stars, like people, have had their own proper names, such as Vega or Deneb. But today proper names are widely used only for the brightest few dozen stars and it's a good thing. Star names are poetic and embody old constellation lore (usually in garbled Arabic), but confusion runs wild. "Deneb" to most people interested in astronomy means the brightest star in Cygnus. But the same name has also been bestowed, at some time, on at least five other stars. It simply means "tail," a body part that a lot of constellations possess.
Moreover, there are simply too many proper names to ever remember. The Bright Star Catalogue, 5th edition, lists more than 800 of them. Every astronomer knows what you mean by Sirius or Polaris, but not one in a hundred could identify Pishpai (Mu Geminorum), Alsciaukat (31 Lyncis), Dhur (Delta Leonis), or Zujj al Nushshabah (Gamma Sagittarii).
More tractable is the Greek-letter system introduced by the German astronomer Johann Bayer in 1603. In his beautiful star atlas, Uranometria, Bayer identified many stars in each constellation with lower-case Greek letters. He often named a constellation's brightest star Alpha, then sorted the rest into brightness classes and assigned letters within each class in order from the head to the feet of the traditional constellation figure.
Bayer's letters caught on immediately. They are used with the Latin genitive of the constellation name, so the leading star in Centaurus is Alpha Centauri ("Alpha of Centaurus"). Back when most educated people knew Latin and Greek this phrasing flowed off the tongue naturally, but today it's many skywatchers' first exposure to the Greek alphabet and Latin declensions. Sooner or later everyone who deals with stars has to sit down and learn the Greek letters (listed below) and the genitives of the 88 constellation names (listed in the back of most astronomy handbooks).
There are swarms of stars per constellation but only 24 Greek letters. Sometimes one letter is used repeatedly with superscripts to cover several adjacent stars. But as more and more stars needed names because of better sky surveys, astronomers adopted numbers. Around 1712 John Flamsteed, England's Astronomer Royal, began numbering stars in each constellation from west to east in order of right ascension a big help when looking for a star on a map. For instance, 80 Virginis is east of 79 Virginis and west of 81 Virginis (at least in the coordinate system Flamsteed used the equinox-1725 system which still matches today's celestial east and west pretty well).
All bright stars were numbered whether they had a Greek letter or not, which is why Alpha Lyrae is also 3 Lyrae. In all, 2,682 stars received Flamsteed numbers. The highest Flamsteed number within any constellation is held by 140 Tauri.
There are occasional confusions. When the constellation borders were formalized in 1930, a number of Flamsteed stars found themselves stranded in exile. Thus the star 30 Monocerotis is today considered to be in Hydra, and 49 Serpentis is in Hercules. Such confusing designations are best swept under the rug, never to be used.
Nobody got around to numbering stars farther south than could be seen from England. So in far-southern constellations one often encounters upper- and lower-case Roman letters, such as g Carinae and L2 Puppis. Roman letters were applied all over the sky by various star mappers from Bayer on, but in the northern sky they have largely passed out of use. Read more...