From the September 2021 issue

Celebrating a century of variable star astronomy

Since its founding in 1911, the American Association of Variable Star Observers has been an indispensable organization for amateur astronomers, engaging stargazers in exploring the night sky.
By | Published: October 5, 2021 | Last updated on May 18, 2023
This photo was taken at the Annual Meeting of the AAVSO on Nov. 10, 1917, held at Harvard College Observatory in Cambridge, Massachusetts. Among the attendees are Annie Jump Cannon (seated, third from the left) and Henrietta Swan Leavitt (seated, fourth from the left). The association’s founder, William Tyler Olcott, is directly behind Ida E. Woods, the woman standing in the front row.
Humans are natural explorers. Once we were clothed, fed, and found shelter, we started wondering, “How does nature work? What’s around us? How did we come to be? What is our place in the universe?”

To answer these questions, we developed theories about the motions of the Sun and the Moon; we predicted eclipses and discovered the principles and laws that govern the natural world. Astronomy became part of our everyday life and our culture: We used stars to navigate our planet, tell us when to rotate our crops, and define our seasons. We incorporated starry nights and comets into our art. And early on, we noticed that some stars change their brightness in systematic ways. We recorded these stars in our most valuable historical and religious documents for posterity.

Variable star observers

Over time, astronomy became a profession for some and a hobby for others. Researchers started forming groups of like-minded enthusiasts to observe the sky, attend lectures, and discuss recent discoveries. Within those groups, they started discussing whether there was a way for those without formal preparation — amateur astronomers — to participate in scientific discovery.

Since the first AAVSO annual meeting in 1916, the event has grown immensely. This photo shows more than 70 attendees at the 108th Annual Meeting of the AAVSO in Las Cruces, New Mexico, which took place in October 2019. (The more recent 109th Annual Meeting was held virtually due to the pandemic.) The author stands third from the right in the front row.
In 1911, amateur astronomer William Tyler Olcott officially formed the American Association of Variable Star Observers (AAVSO) under the guidance of Harvard College Observatory Director Edward C. Pickering. The association’s purpose was to assist and organize amateur astronomers to collectively work to observe and understand some of the most dynamic and fascinating objects in the universe: variable stars.

Variable stars undergo brightness changes for reasons that are part of their nature and have nothing to do with cloud cover or flickering caused by Earth’s atmosphere. By continuously observing those changes, we can discover intrinsic properties of these stars, understand their mechanics, and derive the physical laws describing their behaviors.

The AAVSO has become an invaluable resource and enabler of this type of research. As scribed in our incorporation document, “the Corporation is constituted for the purpose of the promotion of Variable Star Astronomy and kindred objects.” This statement showcases the foresight of our founders, who recognized that variable stars could not be the only celestial objects that changed in brightness. They wanted to give flexibility to future researchers and observers, allowing them to participate in relevant research on any new and exciting discoveries using whatever means human ingenuity enabled.

The author gives a talk for an audience of professional astronomers on the value of AAVSO observations, at a September 2019 conference in Yerevan, Armenia.
Stella Kafka
Over the decades, AAVSO observers — aided by technological advances and access to sophisticated equipment — have progressed alongside professional astronomers in their quest for knowledge. AAVSO observers started with visual observations, with or without the aid of binoculars or a telescope, to compare the brightness of variable stars with non-variables. They sent their reports to the AAVSO Headquarters in Cambridge, Massachusetts, for inclusion in the AAVSO International Database (AID).

Evolving technology slowly began to enrich these successful visual observations. In the years following World War II, the AAVSO started our Photoelectric Photometry program, encouraging members to use emerging technology to obtain high-precision data on bright variable stars. This dramatically increased the accuracy of observations for those stars and added a new component for AAVSO observers: It enabled them to acquire data using filters, including colors, as opposed to naked-eye only observations.

Community and communication

An essential part of the AAVSO has always been building an international community of individuals united under the umbrella of astronomy. The organization’s eagerly anticipated annual meetings, starting with the first one in November 1917, are places to exchange ideas, celebrate scientific results achieved with AAVSO data, build new friendships, and “geek out” together. In 1972, the AAVSO founded the Journal of the American Association of Variable Star Observers (JAAVSO) to disseminate information from scientific presentations given at the AAVSO meetings. The journal also welcomed content on variable star scientific discoveries, authored by both professional and amateur astronomers.

As the internet provided the means for immediate communication, mailed letters, paper alerts requesting observations, and telegrams were replaced by email groups, digital alerts, and online forums. Requested data became instantly available. Observers shared targets immediately and participated in animated discussions and clarifications on observing campaigns. Our international community started communicating in real time.

RS Puppis, imaged here in stunning detail by the Hubble Space Telescope, is a Cepheid variable whose brightness varies by roughly a factor of five every 41 days.
NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-Hubble/Europe Collaboration. Acknowledgment: H. Bond (STScI and Penn State University)

Keeping up with the times

By the last decade of the 20th century, instruments, filters, and larger telescopes had become even more affordable to citizen astronomers. In the 1990s, our observers started attaching CCD cameras to their telescopes, pushing their observing capabilities to ever-fainter objects. They began purchasing various filters to provide color information on stars of interest. And they started using DSLR cameras for data acquisition.

By the early 2000s, appropriate software tools became essential to extract photometry, access star-finding charts with suitable comparison stars, submit observations online, and discuss and publish results. The AAVSO adjusted to these new demands by focusing on our online presence and offered resources. We expanded our educational and training portfolio to include manuals disseminated through our website, online courses, and a peer-mentoring group. We also developed software to facilitate data analysis.

The AAVSO has a long and storied history. This year, the organization celebrates its 110th anniversary.
In 2006, with the help of volunteers, we built our Variable Star Index (VSX) — a supercatalog of current information on variable stars, which has become the backbone of our databases and a valuable reference for researchers worldwide. We formed an active help desk to immediately assist observers. And we started focusing even more closely on data validation, providing feedback to observers when we find discrepancies. The latter is a primary reason why professional astronomers trust our database — we are thorough.

And the professional astronomical community’s trust in our work has only increased. More and more professional astronomers request AAVSO observers’ help to collect and analyze critical data for their research. We have joined high-profile international collaborations, including with the Transiting Exoplanet Survey Satellite (TESS) and the All Sky Automated Survey for SuperNovae (ASAS-SN). We have initiated two new databases — for exoplanets and for spectroscopy — to accommodate small telescope data for these fields and expand the impact of our observers’ data in these areas. And we are now accepting relevant data using the new generation of detectors: CMOS cameras. We are interested in exploring the use of such equipment, especially as manufacturers indicate they may begin phasing out support for CCDs.

This 1917 letter, written by AAVSO founder William Tyler Olcott to Helen Swartz, expresses his regrets that Swartz could not attend the 1917 meeting. It also informs Swartz of her election as a council member of the organization, along with Charles McAteer, for the following year.
The AAVSO itself has also grown with time. Our AID photometry database now hosts more than 44 million data points, with 2 million of those collected in 2020 alone. VSX contains more than 2 million stars. Our data appear in a multitude of peer-reviewed astronomical manuscripts and press releases, while our observers are the superstars among groups of scientific collaborators, thanks to their ability to uniquely respond to alerts and provide data from all over the world. As large space- and ground-based professional photometric surveys reveal new stellar wonders, we are invited to pursue them. The observers, volunteers, researchers, educators, and students of the AAVSO are more essential than ever for the progress of science. We live in the renaissance of variable star astronomy.

Join us!

Astronomy is a scientific field where non-specialists can make a meaningful contribution to research with visible impact. If you have access to binoculars, a telescope, a DSLR camera, a CCD camera, or a spectrograph, join us. If you are interested in learning more about variable star work, register for our free webinars. If you are working on a project as part of your student coursework, publish it in the JAAVSO. If you want to learn how to observe with various techniques, we have all the necessary material to help you get started, and we will be by your side as you engage with the projects of your choice. Take advantage of our free resources. Join the conversations.

Whether you are an astronomy enthusiast, an observer, a learner, or an explorer, become a member and join our quest for knowledge. When it comes to understanding the cosmos, one of the only means we have in our hands is light — which, when studied the right way, can reveal a four-dimensional picture of some of the most dynamic and diverse phenomena in the universe!

Oct. 10, 2021, marks 110 years of the AAVSO’s work and contributions. It’s been 110 years of hard work, building a unique community of astro-enthusiasts who collectively explore the universe and actively participate in scientific discovery. Those individuals leave a rich legacy of knowledge and an outstanding personal contribution to science. Anyone can do it, and the AAVSO is here to help you start your journey exploring the stars. Join us!