What Is The Name of That Star?
"What is the name of that star?" This is a question that many a young observer has asked their mentors. As astronomers we know that stars have many names - proper names, Bayer and Flamsteed Designations, and the Henry Draper Catalogue, for example.
Databases like the AAVSO International Database need a way to uniquely identify objects within the database. While people may (or may not!) be able to recognize different names for the same star, databases decidedly need a unique identifier, or name, in order to specifically identify each star.
The Harvard Designation  has served us well. Being tied to a position in the sky has its advantages. However, it also has its problems - especially with high proper motion stars that are now not anywhere close to where their epoch 1900 coordinates suggest. Also, the structure of the designation limits how many designations we can assign. Basically, we can only have 26 stars within a common RA/Declination (1234+56A - 1234+56Z). Now that tens of thousands of variable stars are known, and hundreds of thousands are expected to be discovered as modern surveys come online, we need a more flexible system.
The AAVSO Unique Identifier (AUID) is in an alphanumeric "license plate": 000-XXX-000 where the 0's are 0-9 and the X's A-Z. This gives us 17,576,000,000 possible combinations - enough to keep us busy for a long time! Every star in the AAVSO International Database  has had an AUID assigned. As we add new stars, we will assign new AUIDs. We have also begun a project to make sure that all "names" of stars in the database are also unique. That way you can always use the name of a star to submit data, plot a light curve, make a chart, etc.
Within the databases that the AAVSO maintains each different object has its own AUID number. As far as the database is concerned, this AUID is the object's name. This name, or key, is used to uniquely identify objects across various databases.
As an observer you may never come across an AUID or really need to know what, for example, the AUID of SS Del is (000-BCM-129, for the curious). As astronomy moves increasingly toward data mining, however, the knowledge of what "glues" our various databases together may be increasingly important, especially to those writing utilities to access or reference various databases.
The Variable Star Index (VSX)  is an extremely useful tool that searches mulitple databases for information on variable star objects. If you are not familiar with, give it a try today!