American Association of Variable Star Observers

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The American Association of Variable Star Observers (AAVSO) is a US association for the study of variable stars. The association was founded in 1911.[1][2]


The AAVSO collects, analyzes, publishes, and archives observational data of variable stars. A large proportion of the data is derived from observations by amateur astronomers. This is crucial because observing these stars is still time-consuming today, and professional astronomers often do not have enough time to observe stars over an extended period of time.[3] The decisive factor for variable stars is the course of the light curve over a longer period of time, from which conclusions can be drawn about the processes in the stars.

RS Ophiuchi – AAVSO light curve of a brightness outburst in 2005

Regular AAVSO light curve of the red giant Mira

AAVSO International Database

The AAVSO database currently contains about 34 million observations of variable stars, with some data series going back over 100 years. Each year, about 1 million new data are injected into the database by 700 observers. More than two-thirds of the data come from outside the United States. Among other things, light curves can be generated from the data.[4]

Variable Star Index

The Variable Star Index (VSX) is an online catalog that currently provides data on about 600,000 stars, most of which are variable.[5] Various other data sources, such as the General Catalogue of Variable Stars (GCVS), are integrated and combined. As a result, this catalogue contains a large amount of data with a relatively recent status, but it does not correspond to a homogeneous data set, since the sources are often different. The catalog also offers its own classification of variable stars, which is very similar to that of the GCVS but has some differences in detail. Overall, the number of star classes is slightly higher than in the last version of the GCVS.


The AAVSO is an international non-profit organization. Today it is headquartered in Cambridge, Massachusetts with members in over 100 different countries. This makes it the largest association for the observation of variable stars.[6]


The minor planet (8900) AAVSO is named after the organization.

See also

  • Federal German Working Group for Variable Stars

Web links

Individual references

  1. M. Saladyga: The“Pre-Embryonic” State of the AAVSO: Amateur Observers of Variable Stars in the United States From 1875 to 1911. in: Journal of the American Association of Variable Star Observers. 27, no. 2, 1999, pp. 154-170. bibcode:1999JAVSO..27..154S.
  3. T. Ferris: Seeingin the Dark: How Amateur Astronomers Are Discovering the Wonders of the Universe. Simon & Schuster, 2003, ISBN 0-684-86580-7, p. 54.
  4. The AAVSO International Database.Retrieved January 29, 2019 (English).
  5. The International Variable Star Index.Retrieved January 29, 2019 (English).
  6. Vision/Mission.Retrieved 29 January 2019 (English).