Astronomer's Toolbox

Where do variable stars get their names?

From the General Catalog of Variable Stars, we find that the naming convention for variable stars (many of which are X-ray sources) is not as straightforward as you might think. They start at R (instead of A) and go through the alphabet and double alphabet in a non-intuitive way.

Letters
 
# of them
R, S, ..., Z,                     
                
9
RR, RS, ..., RZ, SS, ST, .., SZ, TT, ..., ZZ,
 
    
45
AA, AB, ..., AZ, BB, ...QZ,                 
 
 
    
280  (but no J !)

When they get to this point, instead of moving on to AAA or RRR, they go to V and start with the number after the total number of previously named objects (9+45+280).

V335, V336, ...

As of a recent (1995) name list, the total number of designated variable stars has now reached 31,193. Sagittarius has the most of any constellation: it's now up to V4333 Sgr.