A single constellation may contain fifty or more stars, but there are only twenty-four letters of the Greek alphabet, so, when he ran out of Greek letters to use for identifying the stars of a specific constellation, Bayer began using lower-case Latin letters. For example, Bayer assigned three stars in the constellation Carina as " s Carinae ", and another star in Centaurus as " d Centauri ", to indicate "s of the Keel" and "d of the Centaur", respectively.
Within constellations having an extremely large number of stars, Bayer eventually advanced to upper-case Latin letters, ending with the upper-case letter "Q". Is Alpha Always the Brightest Star? For the most part, Bayer assigned Greek and Latin letters to stars in order of apparent brightness, from brightest to dimmest, within a particular constellation. Traditionally, the stars were assigned to one of six magnitude classes, and Bayer's catalog lists all the first-magnitude stars, followed by all the second-magnitude stars, and so on.
However within each magnitude class, there was no attempt to arrange stars by relative brightness. Bayer did not always assign Greek and Latin letters to stars in this manner.
Usually the stars were roughly ordered from the head to the feet or tail of the figure like the stars in the Big Dipper. Bayer Designations in Orion Orion provides a good example of Bayer's method. Remember that the "lower" the magnitude, the "brighter" the star. Additionally a "2nd-magnitude" star has a more precise magnitude between 1. In , the International Astronomical Union specified a definitive set of 88 constellations , based on the groupings introduced by:. The modern constellations contain a mixture of mythological characters e.
Perseus, Andromeda, Orion , animals e. Taurus, Scorpius, Canis Major , scientific apparatus e. Microscopium, Sextans and Caelum the chisel and everyday objects e.
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 star names.
More tractable is the Greek-letter system introduced by the German astronomer Johann Bayer in 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 star names 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 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 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, stars received Flamsteed numbers. The highest Flamsteed number within any constellation is held by Tauri. There are occasional confusions. When the constellation borders were formalized in , 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 L 2 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. By the 19th century all these naming efforts were falling far short of the mushrooming need. Telescopes were revealing stars by the hundreds of thousands, every one of them an individual crying out for its own identity.
Meticulous and industrious, Bonn Observatory director Friedrich W. Argelander — organized the most massive star-cataloguing project up to his time, creating a star atlas and catalog that remained in everyday use by astronomers for the next century. In the German astronomer F. Argelander at Bonn Observatory began measuring star positions with a 3-inch refractor to compile a gigantic list, the Bonner Durchmusterung Bonn Survey. The BD eventually included , stars as faint as about magnitude 9.
Stars within each band were numbered in order of right ascension; constellations were ignored. The Cordoba Durchmusterung CD or CoD completed the job, picking up , more on its way to the south celestial pole. All in all, Durchmusterung , or "DM," star names were bestowed on a grand total of 1,, stars.
The BD, with its detailed star charts and its reliable, well-checked list of positions, remained an essential everyday tool of working astronomers for nearly a century.
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