Those of you with an interest in astronomy may often come across a named star in the literature, like Polaris, or Alpha Centauri, or some impenetrable and unromantic catalog number. Astronomy has a lot of historical and traditional nomenclature systems, so I thought I’d give you a brief glimpse at some of them so you would have some idea how the stars get their names.

Stars that have common names usually go way back, to stars named in antiquity. Most of the named stars you’ll see in star charts or read about in magazine articles and science fiction stories were known to the ancients, and a surprising number of them are still in common use. A good list of these are the 57 navigational stars listed in the Nautical Almanac. Although some originated in Classical mythology, or were named by European seafarers when they first ventured south of the equator, the vast bulk of them came to us from the Arabs, and many of those trace back to ancient dialects of that language; today their meanings are in doubt and debated by scholars.
Some modern names are also Latinized, so they would probably be meaningless to an Arabic speaker.

You have no doubt heard many of these, like Altair, Vega, Betelgeuse, Aldebaran, Arcturus, Sirius, Procyon, Castor, Pollux, Antares, Capella, Spica, Deneb, Regulus and so on. These are usually bright stars, or medium-bright stars in areas where there are no other bright stars nearby. Some of them have real jawbreaking handles, especially those from Arabic, like Zubenelgenubi, Unukalhai, and Ras-algethi. I guess these names have survived because they provide us a link to that dim past when Arab dhows and caravans roamed the empty places of the earth under dark and starry skies. We know what some of these names translate to, things like “Rival of Mars”, or “Heart of the Lion”, that sort of thing. Writing them down in a logbook connects you to an ancient past, and an honorable tradition.

In the 1600s, the German astronomer/uranographer Bayer first introduced the Bayer designations you are also no doubt familiar with. They consist of a lower case Greek letter followed by the genitive case of the constellation it resides in, such as Alpha Centauri, Beta Pegasi or Gamma Andromedae. Each constellation has up to 24 of these (the number of letters in the Greek alphabet) and the order in the alphabet is correlated with the brightness of the star (although there are many exceptions to that rule). Even stars with a common name may have a Bayer designation, so for example, Polaris is Alpha Ursae Minoris, and Betelgeuse is Alpha Orionis.

There are from 6 to 8 thousand stars visible to the naked eye, about three to four thousand at any one time, so more names were clearly needed. An astronomer called Flamsteed introduced the Flamsteed Numbers, which also numbers the stars by brightness in each constellation. So scattered about star charts you will see notations like 51 Pegasi. I don’t know too much about Flamsteed numbers, I don’t know if he attemped to give a number to every naked eye star. At any rate, the system is rarely used any more unless the star is famous for some reason, or has attracted the attention of researchers. Because of precession, some of these stars have moved across constellation boundaries as the celestial coordinate system shifts with the earth’s wobble, so they may have a Flamsteed number for an adjoing constellation, not the one they’re in. But to correct that would cause undue confusion.

All stars above a certain limiting magnitude also appear in star catalogs, and this is the third level of star name you are likely to run into. The catalogs are of different limiting magnitudes (some go deeper than others). Of course, not all the stars are cataloged, there are just too damn many of them. The most extensive catalogs go down to about 9th or 10th magnitude, but fainter than that, the number of stars in the galaxy just goes up explosively. Catalogued stars give the initial of the catalog followed by a number. Most of the numbers are ordered in the astronomical convention, by increasing right ascension, (they increase to the east), so that the higher numbers rise later in the evening. However, precession since the catalogs were first compiled may have interrupted this order. Sometimes, a higher number may be west of a lower one. Like I said, astronomy has a lot of historical artifacts and quirky anomalies. You get used to it.

Some common catalogs you may see are the GC (Boss General Catalog), the HD (Henry Draper) or the SAO (Smithsonian Astrophysical Observatory). You may also come across the BD (Bonner Durchmusterung) a German 19th century catalog, or the CoD (Cordoba Durchmusterung) the BD’s southern hemisphere counterpart. Cordoba is an important observatory in Argentina where the CoD was compiled. Many of these catalogs have detailed charts associated with them. which are all out of print now, and observatories protect their copies ferociously. Other catalogs exist in digital formats, such as the Hubble Guide Star Catalogue and the TYCO and Hipparchos astrometric satellite catalogs. Many of these advanced catalogs use complex numbering systems that incorporate a rough approximation of the star’s coordinates into its catalog number. You need instructions.

THere are many other specialized catalogues with only one type of object, such as the ADS (American Double Star catalog) and variable stars have their own unique numbering system, by alphabet code (non-linear, it jumps around the alphabet so variables won’t be confused with similarly named objects from other catalogs)in each constellation. When the letter combinations run out they switch to numbers. So when you see a designation like S Fornacis or RR Lyrae or V221, that’s what you are looking at.

If any of you are researching something like this and you can’t figure it out on the internet, post your question here and I’ll do my best to answer it. I don’t know it all, but I know where to look it up.