The term 'Variable Star' originally referred to those stars that vary in their brightness. All stars vary in one way or another. There are about 20,000 recognized variable stars listed in the well-known Catalogue of Variable Stars (See bibliography). The major types of variable stars are listed below.

Pulsating Variables		Number	Explosive Variables		Number
C	Classical Cepheids	696	N	Novae	203
I (L)	Irregular Variables	1687	Ne	Nova-lie Variables
M	Mira Ceti	4600	SN	Supernovae	7
SR	Semi-regular Variables	4423	RCB	R Cr Borealis Stars	31
RR	RR Lyrae Variables	4423	RW (I)	RW Aur, T Tauri Stars	1005
RV	RV Tauri Stars	100	UG	U Geminorum Stars	210
C	Cephei Stars	14	UV	UV Ceti (flare) Stars	100
SC	Scuti Stars	12	Z	Z Camelopardalis Stars	19
CV	CVn Stars 28

Eclipsing variables of all kinds total 4018. The more recent designations in the above table are in parenthesis. Individual variable stars within each constellation are named by letters and numbers that indicate their order of discovery. The first variable found within any constellation has the letter R assigned to it (example: R Coronae Borealis). Subsequently discovered variables take the letters S, T ... to Z; then RR, RS, RT ... SS, ST, and so on through ZZ.

After ZZ, variable stars are named starting from the beginning of the alphabet with AA, AB, AC ... through AZ, then BB, BC through BZ, and son on through QZ.

The preceding will take care of 344 stars in each of the constellations. If there are still more variables, they receive numbers from 335 on, preceded by the letter 'V' and followed by the constellation. An example would be V 335 Cygni, being the 335th variable star discovered in the constellation Cygnus.

Copyright (c) 1997-99 Michael Erlewine