The AAVSO is a nonprofit worldwide scientific and educational organization of amateur and professional astronomers who are interested in stars that change in brightness—variable stars. The AAVSO was incorporated in the Commonwealth of Massachusetts in 1918 as a non-profit scientific and educational organization. Today, as an independent, private research organization headquartered in Cambridge, Massachusetts, with members and observers in 52 countries, and an archive of over 19 million variable star observations, it is the world’s largest association of variable star observers. Membership in the AAVSO is open to anyone—professionals, amateurs, and educators alike—interested in variable stars and in contributing to the support of valuable research. Professional astronomers have neither the time nor the telescopes needed to gather data on the brightness changes of thousands of variables, and amateurs make a real and useful contribution to science by observing variable stars and submitting their observations to the AAVSO International Database.
