American Association of Variable Star Observers
The AAVSO at Harvard College Observatory coordinates variable star observations made largely by amateur astronomers and it is the world’s largest association of variable star observers in existence. The web site offers a subject index to their journal, online versions of the AAVSO Observing Manual in HTML and PDF, a variable star chart database and more.
American Astronomical Society (AAS)
Established 1899, is the major organization of professional astronomers in North America. Publishers of The Astronomical Journal and The Astrophysical Journal, the society’s web site offers resources to members.
Association of Universities for Research in Astronomy
A consortium of 34 U.S. institutions and 7 international affiliates: universities, and educational and other non-profit institutions that operate world-class astronomical observatory centers.
International Astronomical Union (IAU)
Promotes and safeguards the science of astronomy in all its aspects through international cooperation. Members are professional astronomers all over the world, at the Ph.D. level or beyond and active in professional research and education in astronomy. It is the official star naming entity, and provides a guide on the subject of naming astronomical objects
The world's largest space-interest group, is dedicated to inspiring the public with the adventure and mystery of space exploration.