American Association of Variable Star Observers

Since its founding in 1911, the American Association of Variable Star Observers (AAVSO) has coordinated, collected, evaluated, analyzed, published, and archived variable star observations made largely by amateur astronomers and makes the records available to professional astronomers, researchers, and educators. These records establish light curves depicting the variation in brightness of a star over time.

Since professional astronomers do not have the time or the resources to monitor every variable star, astronomy is one of the few sciences where amateurs can make genuine contributions to scientific research. The AAVSO International Database currently has over 20 million variable star estimates dating back over 100 years. The 20-millionth observation was received into the database on February 19, 2011, during the AAVSO's 100th year of existence. It receives nearly 1,000,000 observations annually from around 2,000 professional and amateur observers and is quoted regularly in scientific journals.

The AAVSO is also very active in education and public outreach. They routinely hold training workshops for citizen science and publish papers with amateurs as coauthors. In the 1990s, the AAVSO developed the Hands-On Astrophysics curriculum, now known as Variable Star Astronomy (with support from the National Science Foundation (NSF)). In 2009, the AAVSO was awarded a three-year $800,000 grant from the NSF to run Citizen Sky, a pro-am collaboration project examining the 2009-2011 eclipse of the star epsilon Aurigae.

The current director of the AAVSO is Stella Kafka, who took over from Arne Henden in February 2015. The previous director of the AAVSO for many decades was Janet Mattei, who died in March 2004 of leukemia.

The AAVSO headquarters were originally located at the residence of its founder William T. Olcott in Norwich, Connecticut. After AAVSO's incorporation in 1918 it de facto moved to Harvard College Observatory, which later officially provided an office as the AAVSO headquarters (1931–1953). After then it moved around Cambridge before purchasing their first building in 1985 - The Clinton B. Ford Astronomical Data and Research Center. In 2007, the AAVSO purchased and moved into the recently vacated premises of Sky & Telescope magazine.

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