Online Astronomy eText: The Sky
Star Names
(also see Stars and Constellations, and Name That Star -- Not!)

"Why did not somebody teach me the constellations, and make me at home in the starry heavens, which are always overhead, and which I don't half know to this day?" -- Thomas Carlyle, 1880.

     In discussing star names and their history, some use must be made of Greek names and letters. Until the twentieth century, any well-educated person was expected to be familiar with Latin and Greek, but that cannot be expected, today. For that reason, any Greek words or letters used on this page have a hidden "title" which can be viewed by holding the cursor over them. For instance, if you hold the cursor over κυνόςουρα, you should see the transliteration "Cynosūra".

     When we look at the sky, there are no names next to the stars; and no name we assign to a star truly belongs to it, or necessarily says anything about it as a real object. It is merely our way of saying "Look at this star over here, not that one over there." Given the vast numbers of stars scattered across the sky, such appellations are necessary, to avoid total confusion; and there is something comforting about knowing what a given star or constellation is called, even if it is just a name established by some sort of convention.

The Big Dipper
The Big Dipper.

     Imagine how difficult it would be to specify one particular star, out of the multitude found in even a small area of the sky, without any way of saying which star you are talking about. (Noel Carboni, apod060317)

Note: It has just been brought to my attention that one of the references I used for the following is not to be trusted; as a result, I am not sure which statements made below are correct, and which are not. Until this note is removed, although the discussion below can still serve as an example of the confusion which can be associated with star names, it is subject to revision as needed.

Common, or "Proper" Star Names
     Over the course of history, most stars have been given names, to differentiate them. Unfortunately, the same name was occasionally used for different stars, and many stars have been given different names by people living at different times (or, of course, in different parts of the world). As an example, the current Pole Star (or North Star) is called Polaris, in acknowledgement of its status. But in ancient Greek (Hellenic) times the Celestial Pole was closer to Kochab than to Polaris, and Polaris was called Phoenice, borrowed from Ursa Phoenice, the Phoenician Bear, the name given to what we now call the Little Bear (or Ursa Minor) when the constellation was created out of parts of other constellations by Thales, about 600 B.C.E. Later, Ursa Phoenice became κυνόςουρα (Cynosūra), the Dog's Tail, and that name was used for the star for more than a millennium. It is only in the last few hundred years, as precession has brought the Celestial Pole closer and closer to Polaris, that it acquired its present name. Similarly, Vega, one of over forty names used for the brightest star in the constellation of Lyra, was once used as the name for the constellation, itself.
     Some of the names which we use for stars and constellations are the names of mythological figures, such as Orion the hunter, Hercules the strong-man, and Castor and Pollux, the Twins. Others describe the star's position in the sky. As an example, Sirius is based on a Greek word meaning 'scorching', because its heat was thought to add to that of the Sun, to produce the "dog days" of late summer. It is also called the 'Dog Star', because of its position in Canis Major, the Big Dog. The name of the bright star to its northeast, Procyon, is based on the Greek 'pro kion', or 'before the dog', because being further north than Sirius, it rises before it, even though it is further to the east.

The "common" names of the stars in the Big Dipper.

Bayer Designations
     In 1603, while preparing a "modern" star map, Johann Bayer decided to avoid the confusion associated with having different names for different stars by using the letters of the Greek alphabet to create what we now call "Bayer designations". The brightest stars in a constellation were given letters at the beginning of the alphabet, and fainter stars were given letters further along the alphabet. Thus the brightest star would be α, the next brightest β, and so on. He did not follow only this rule, however. When, as in the case of the Big Dipper, there are a number of stars of roughly equal brightness, he used their positions to decide which would come first, and which would come next. In Orion, which contains two first magnitude stars, Betelgeuse, which is on "top" (being one of Orion's shoulders), is designated α, and Rigel, which is on the "bottom" (being one of Orion's knees), is designated β, even though Rigel is about thirty percent brighter than Betelgeuse. Similarly, in the Big Dipper, the stars are labeled according to their position, with Dubhe, at one end of the bowl of the Dipper, being designated α, and the other stars being designated β, γ, δ, ε, ζ and η in order of position around the bowl and down the handle, even though one of them, Megrez, is substantially fainter than all the others.
     The Bayer designation does not consist of only the Greek letter assigned to the star. It also includes the possessive form of the constellation's Latin name. Dubhe is α Ursae Majoris, or "alpha of Ursa Major", while Betelgeuse is α Orionis, or "alpha of Orion". On maps, only the Greek letter is shown next to the star, because the constellation is inferred from the overall position in the sky, or indicated by an outline of the area covered by the constellation, and the name of the constellation, somewhere inside that outline. In tables, the Greek letter is combined with a three-letter abbreviation of the constellation name, so that Dubhe is α UMa, and Betelgeuse is α Ori. Similarly, Polaris is α UMi, or α Ursae Minoris, meaning that it is one of the brightest or most important stars in Ursa Minor, while Kochab, which is equally bright, but no longer serves as the Pole Star, is β UMi, or β Ursae Minoris.

The Bayer designations of the stars in the Big Dipper.
Alcor, which has no Bayer designation, is indicated by its Flamsteed number.

Flamsteed Numbers
     In the late 1600's, John Flamsteed extended Bayer's idea, using numbers instead of letters (in a sense, Bayer was numbering them as well, since the letters of the Greek alphabet were used as counters, as well as letters). Instead of just numbering the brighter stars, as Bayer did, Flamsteed assigned numbers to all the naked-eye stars (that is, all the stars visible in a dark sky, without optical aid). However, instead of using low numbers for brighter stars and high numbers for fainter stars, which is essentially what Bayer was doing, Flamsteed numbered the stars according to their right ascension, so that the westernmost star in a constellation was assigned the number 1, the next star to the east of that in the same constellation was assigned the number 2, and so on.

(more to follow)

Variable Star Names
     (to be added later)

Catalog Numbers and Positional Designations
     (to be added later)