How Stars Are Named

Have you even wondered how stars and other celestial bodies got the names they have? Do we call the planets after Greek gods? Or were the Greek gods named after the planets? There are currently three different types of naming conventions that are used to name stars and give them designations that are recognized on an international level. Because of the way the stars are named using these conventions, it is highly conceivable that each star or celestial body has more than one name, which is used interchangeably with the others. Confusing? For the average stargazer, yes, but each of the names holds significance to the astronomical community and helps us understand the star in question.

Let’s take a look at the basics of how astronomers name the many different stars in our sky and the significance of each name.

Common names are the everyday names that we know for the stars and planets in the sky, such as Venus, Mars, Pluto, etc. It is unknown when this convention started. Historically, in the international astronomical community the common names come from mythological figures. Venus was named after the Roman goddess of love. The star Rigel, located approximately in the foot of the constellation Orion and the brightest star in the figure, is Arabic for "the foot of the great one." Betelgeuse, the red star at the shoulder of Orion diagonal from Rigel, is also Arabic and means (approximately) "the armpit of the mighty one." These are the names that the ordinary lay person uses when talking about the stars in the sky. When you say these names, everyone knows what you are referring to.

While using the common naming system does work, eventually astronomers will run out of names when they exhaust the world’s mythological deities, creatures, and more. In about 1603 astronomers developed a systemic naming convention to use instead, called the Bayer Naming System.

With this system, the brightest stars in the sky and in their individual constellations are given a name that includes the Latin possessive name of the constellation and a Greek letter of designation. This naming convention is approximate, as some stars which carry a Greek letter further down the alphabet may be brighter than the ones named before it. So let us consider Betelgeuse. It is known in the Bayer system as Alpha Orionis with Rigel being Beta Orionis. If we break this down and look at the parts it reads as follows:

Common name: Betelgeuse

Constellation: Orion

Latin Possessive: Orionis

Bayer name: Alpha Orionis (Alpha is the first letter of the Greek alphabet)

We have discussed the common names of the stars and the Bayer System names of the stars, but once again astronomers had more stars and celestial bodies to name and only so many Greek letters in the alphabet. You can’t very well call a star Alpha Beta Kappa Delta Omega Something; that’s a bit unwieldy. So to handle the infinite amount of stars that need to be named by astronomers, the Flamsteed System was developed about 1712.

Once again, the constellations are used in their Latin possessive form and then a simple Roman numeral is added before the name, numbering the stars from west to east. The star that is closest to the western edge of the constellation is designated number 1, and so forth, until each has been numbered. So Betelgeuse, in Orion, is called 58-Orionis since it is the 58 closest start to the constellation’s western edge. Remember, Orion is ‘the hunter’ and because he is holding a bow, Betelgeuse is further in than most realize.

Image Credit : Richard Yandrick (Cosmicimage.com)