Star naming

One of the things you'll notice when looking through references, star maps, or anything that might refer to a star, is that stars have names.

There are three main types of names that a star can have:

• A catalog number
• A name based on how bright it is, and the constellation it is part of.
• A common, proper name.

Most stars have at least one type of name, a lot have two types, and some have all three.

Proper names mostly originate from the names that people have called specific stars for a very long time. Sirius, Achenar, Spica and Fomalhaut to name a few. Most of these stars are the ones that stood out, and so are reasonably bright.

When astronomy started to become more of a science, astronomers needed to be able to label a larger selection of stars, and giving each star a unique name became inefficient. It also made it more difficult to remember. For this reason, a systematic method of labeling stars was developed.

Each star was first classified as being part of a constellation. It was then assigned a letter of the Greek alphabet. Exactly which letter depended on how bright it was relative to other stars in the constellation. Because of this, it is possible to work out a rough description of a star's brightness by looking at it's name. For example, Alpha Centauri is the brightest star in the constellation of Centaurus, Beta Centauri is the second brightest, and so on.

The above system is usually correct, although it stumbles in places. For example, Beta Geminorum is actually brighter than Alpha Geminorum. These mistakes usually occur because for whatever reason, a star's brightness has changed since it was given it's official label. It's not so unusual with variable stars.

With some of today's equipment, millions of stars can be seen. Unfortunately there are only 88 constellations, and only 24 letters available from the Greek alphabet. Because of this, stars are assigned catalog numbers.

There are a variety of star catalogs available, some designating unique identification numbers for every star that is known to exist. Which catalog to use can depend on personal preference, but also keeping in mind that some catalogs are better than others for specific purposes.

Catalog numbers can often be typed into a computer program quite easily when trying to find a specific star, for whatever reason. Most people who are starting out won't need to bother with catalogs at all, since most of the main stars are commonly called by proper names, or the Greek alphabet.