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A century of AAVSO progress: this internationally renowned organization has grown from a handful of amateurs making observations for professional astronomers.

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VARIABLE STARS provide exciting insights about many stages of stellar evolution. Although variables have interested astronomers for more than a century and a half, only recently has the theory of stellar evolution and refined observational technology made clear exactly how important variables are. The centennial of the world's largest association of variable-star observers is therefore a reason for celebration.

During 2011 the American Association of Variable Star Observers (AAVSO) is marking the centennial of its birth. Filled with exciting discoveries and significant astronomical progress, that century witnessed the AAVSO's growth from a handful of amateurs making observations for professional astronomers to a robust organization with the world's largest archive of variable-star observations and historical light curves. But this achievement only happened because of the tireless efforts of the people who made it possible, the variable-star observers and the AAVSO's staff and elected leaders.

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A Century Begins

Connecticut lawyer William Tyler Olcott (1873-1936) announced the founding of the AAVSO and reported the association's first variable-star observations in the December 1911 issue of Popular Astronomy. Olcott made it clear that he formed the association to gather variable-star observations for astronomers at Harvard College Observatory (HCO) in Cambridge, Massachusetts. He recruited observers intensively, attracting an early membership that included many professional women astronomers from New England colleges as well as other American and international observers.

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After six years of effort, Olcott achieved his goal. The members formalized an association, elected officers, and incorporated. Exhausted by the process, Olcott handed over the leadership reins to others with pleasure and satisfaction. He remained as actively involved as his failing health would allow, but many others took up various tasks that he had handled by himself in the early years.

One of those who helped pick up the slack for Olcott was Leon Campbell (1880-1951). A native of Cambridge, Campbell joined the HCO staff as a night assistant in 1899 after graduating from Cambridge High School. His early success earned him a promotion to full observer, roughly akin to a professional astronomer in those days. From 1911 to 1915, Campbell served as supervisor of HCO's Boyden Station in Arequipa, Peru.

Upon his return to Cambridge in late 1915, Campbell immediately joined the AAVSO and began participating in its affairs. He helped Olcott organize observations for publication and advised members on technical aspects of observing variables. Campbell quickly became well known and liked by the members of the AAVSO, and he served as a council member after the group incorporated. Since this work wasn't part of his regular HCO duties, Campbell carried out his AAVSO activities at home.

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In 1925 the AAVSO council recognized Campbell's many years of loyal and dedicated service by formally establishing a new position, AAVSO Recorder, and it elected Campbell to serve. Olcott remained as the corresponding secretary.

Edward Charles Pickering, the director of HCO during the AAVSO's early history, died in 1919. After a three-year search, Harvard University replaced him with a rising young star, Harlow Shapley of Mount Wilson Observatory. Shapley staffed the observatory with younger, highly qualified professional astronomers and rebuilt HCO's aging physical assets.

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As part of a Rockefeller Foundation grant to fund Shapley's modernization program, Harvard received $100,000 to endow a Pickering Memorial Astronomer. When Harvard awarded the endowed chair to Campbell as its first incumbent, Shapley defined Campbell's role as full-time support to the AAVSO. In return, the AAVSO identified the Pickering Memorial Astronomer as synonymous with the AAVSO Recorder. Thus the tie between the AAVSO and HCO was formalized for the first time in 1931.

The 1930s and '40s were exciting times for astronomy despite the economic depression and World War II. Variable-star astronomy at HCO expanded significantly as Cecilia Payne-Gaposchkin and others studied variability in pulsating stars and eclipsing binaries while Campbell and the AAVSO concentrated on the long-period variables. These decades also witnessed astronomers making progress in understanding the mechanisms behind stellar variation.

When Campbell retired in late 1949, Shapley nominated Margaret Walton Mayall (1902-95) as the next Pickering Memorial Astronomer and AAVSO Recorder. Mayall had worked at HCO since the mid-1920s as Annie Jump Cannon's assistant, classifying stellar spectra for the Henry Draper Catalogue. With a degree in astronomy from Radcliffe College, Mayall immediately started broadening the AAVSO's effort, adding entire classes of variable stars to its observing programs. Eclipsing binaries were the first addition at the suggestion of Joseph Ashbrook of Yale University. Mayall's success initiating this program depended not only on observers in the United States, but also several in Sweden and Greece.

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A Change of Plans

Unfortunately, Mayall's freedom to reinvent the AAVSO's observing program ended suddenly. Harvard University had other plans for the observatory that were at cross-purposes with those of Mayall and the AAVSO. Progress at the observatory during Shapley's tenure peaked before World War II, but during and after the war the program deteriorated. When Shapley stepped down as HCO director in September 1952, Harvard appointed solar astronomer Donald H. Menzel as chairman of the Observatory Council, and the interim director of HCO.

Menzel was tasked with reducing expenses and reinvigorating the HCO program. His lengthy list of cost reduction and efficiency improvements included severing HCO's long-standing relationship with the AAVSO. In October 1952, he advised Mayall that the association was likely to lose its financial support and that she should begin planning to vacate the office space at the observatory.

At first Mayall resisted the eviction, but eventually she had to look for alternate arrangements with the help of AAVSO Secretary Clinton B. Ford and the council. In January 1954 the association moved to a tiny office on Brattle Street near Harvard Square in Cambridge. Tirelessly working extraordinarily long hours (even without a salary for at least the first year), Mayall saved the AAVSO from extinction. In 1956 the council changed Mayall's title to AAVSO Director in recognition of her dedication. Aided by financial support and advice from Ford and other members of the council, Mayall kept observers motivated, and the total observations recorded each year after the eviction continued to rise.

When survival was assured as the association found its financial footing, Mayall moved in July 1965 to larger office space on Concord Avenue only a short distance from HCO. Once settled, Mayall began recording observations on IBM punch cards. The observing program was also expanded, adding Cepheid variables, RV Tauri stars, and various eruptive and cataclysmic variables.

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Perhaps the most exciting new study in this era was initiated by AAVSO members Thomas Cragg and Larry Bornhurst at Ford Observatory in California. After astronomers accumulated evidence that the typical cataclysmic variable was part of a binary system, Cragg and Bornhurst followed U Geminorum intensively at minimum light, looking for eclipses during the star's quiescent periods. They found changes that likely reflected events of astrophysical significance (see "50 & 25 Years Ago," page 10).

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Other AAVSO members with large telescopes began undertaking similar studies, cooperating with professional astronomers who eagerly sought their help. Leslie Peltier, at Delphos, Ohio, and a few other AAVSO observers, joined this effort, which helped support profound changes in the theoretical models for cataclysmic variables. The program expanded as fast as Clinton Ford and Charles Scovil at the AAVSO could make new charts for additional stars.

In 1971 Mayall announced her desire to retire, presenting the council with the unfamiliar problem of selecting a new director, since Mayall had started out as Shapley's choice as HCO's Pickering Memorial Astronomer. Furthermore, while Mayall had guided the AAVSO through difficult years, by the time she retired the association was a thriving independent entity.

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After considering many candidates, the council hired Janet Akyuz Mattei (1943-2004), who held a degree in physics from Ege University in Turkey, and another in astronomy from the University of Virginia. She had also gained much variable-star experience during a six-month stint at Maria Mitchell Observatory on Nantucket Island working with the observatory's director, Dorrit Hoffleit.

Mattei took the helm following the AAVSO's annual meeting in 1973 and immediately began dealing with issues involving the observing program and data processing. With the help of Owen Gingerich, Barbara Welther, and others at the Harvard-Smithsonian Center for Astrophysics, Mattei began converting observations on punch cards into light curves. The council also authorized hiring data-entry operators who were devoted full time to transferring observations dating back to 1902 to punch cards.

The publication of Scovil's The AAVSO Variable Star Atlas in 1980 generated considerable interest and drew in new members. The same was true for new observing programs that emphasized monitoring eruptive and cataclysmic variables. The AAVSO program that began with the Cragg and Bornhurst observations of these stars, and the AAVSO's historical light curves for a number of them, attracted the attention of professional astronomers. This led to requests for more monitoring of cataclysmic stars, as well as other variables, in support of orbiting observatories then being launched. The AAVSO was soon providing formal alerts to professional astronomers and those in charge of NASA's satellite observatories.

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One early breakthrough involved the organization's commitment for intensive visual monitoring of U Geminorum and SS Cygni during the late 1970s flight of the X-ray satellite HEAO-1. Astrophysicists were astonished at the correlations between the visual light curves of these stars and the unexpected onset of emissions of both hard and soft X-rays. The results led to significant changes in the theoretical models for this class of variable.

As the AAVSO staff expanded and the Concord Avenue headquarters filled up with punch cards, relocation became necessary. With generous support from Ford, the AAVSO acquired is own building at 25 Birch Street in Cambridge, next door to S&T's offices. The new headquarters were dedicated during the celebration of the association's 75th anniversary in August 1986. Distinguished X-ray astronomer Riccardo Giacconi graced the occasion with an address that pointed to new directions for the AAVSO while celebrating its past accomplishments.

A New Era

The association continued to grow in membership, active observers, and especially the number of observations submitted each year. In the three decades after being evicted from HCO, annual observing totals doubled twice, rising from about 55,000 to more than 200,000 observations per year. In recent years, these annual totals have grown at an even faster rate as more members began observing with photoelectric photometers, and later with CCDs.

The association's educational program was broadened with the introduction of the Hands-On-Astrophysics curriculum codirected by Mattei and Canadian astronomer John R. Percy. It helped interest teachers from around the nation in variable-star astronomy. The association's international participation also grew, especially with the help of meetings held in Brussels, Belgium, in 1990 and Sion, Switzerland, in 1996.

Collaboration with professional astronomers continued to rise. NASA astronomers encouraged AAVSO observers by sponsoring several joint High Energy Astrophysics Workshops with the association, and joint meetings with the American Astronomical Society also emphasized professional astronomers' growing appreciation of the AAVSO. The High Energy Astrophysics Workshops led to a very successful cooperative program to search for the afterglows of gamma-ray bursts.

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One of the crowning achievements of the Mattei era came in early 2004 when she announced that the entire database of observations, from 1911 to the current period, was fully digitized. Light curves could now be generated that revealed the scientific treasure these historical observing records had always represented.

Tragically, Mattei was diagnosed with acute myelogenous leukemia shortly after the AAVSO's third International Meeting and High Energy Workshop in 2003, and she died the following year. Elizabeth O. Waagen, the senior member of the staff", served as the AAVSO's interim director while the council searched for a replacement.

In 2005 the council chose Arne Henden, a professional astronomer at the U. S. Naval Observatory in Flagstaff", Arizona, as Mattei's successor. An expert photometrist, Henden brought a new level of sophistication to the AAVSO's observing programs, encouraging rapid growth in the number and quality of observations added annually to the AAVSO's database.

Members of the association volunteered to work with the staff to upgrade the AAVSO's computer software. They created a sophisticated system of programs that receive, validate, and store observations submitted via the internet. There are also new programs for creating and printing variable-star charts on demand, and generating customized light curves. More than 20 million observations are presently stored in the database. It has every known or suspected variable star, including thousands of new variables discovered during ESA's Hipparcos spacecraft mission and other all-sky surveys. Arguably, the AAVSO International Database (AID) is the most comprehensive catalog of variable stars now in existence.

Effort is underway to add observations of important 19th- and early 20th-century observers to the AID. For example, South African Alexander William Roberts recorded most of his variable-star observations before the founding of the AAVSO. Volunteers in South Africa have recently reduced more than 70,000 of Roberts's observations, and they are now included in the AID.

Henden's energetic style created the opportunity for a move to much more spacious quarters literally next door to the Birch Street office. Under his leadership, the association purchased one of the office buildings on Bay State Road that had served as S&T's some for half a century. Henden, his wife Linda, and the AAVSO staff worked tirelessly to refurbish the new headquarters. Thus, as it did with the 75th anniversary, the AAVSO will celebrate its centennial anniversary in a new location.

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As a new century of variable-star observing begins, William Tyler Olcott's dream of a small band of observers in service to Harvard College Observatory has succeeded beyond his wildest dreams. AAVSO now encompasses a large international group of sophisticated observers in service to astrophysics. And as Henden explains on page 86, the next century will certainly be an exciting one. ?

Thomas R. Williams has served as AAVSO President and is currently its historian. Michael Saladyga is the organization's Technical Assistant and Archivist. Cambridge University Press has just published their centennial history of the AAVSO titled, Advancing Variable Star Astronomy.
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Title Annotation:Astronomical Milestone; American Association of Variable Star Observers
Author:Williams, Thomas R.; Saladyga, Michael
Publication:Sky & Telescope
Geographic Code:1USA
Date:Oct 1, 2011
Words:2358
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