My last post mentioned the Webster Institute for the History of Astronomy at the Adler Planetarium & Astronomy Museum. It’s a place I’m gradually getting to know because for the past few months I’ve been fortunate to volunteer a few hours a week there. It’s a fascinating part of the planetarium, not only because of its exceptional collections and library, but also because of the interesting people who work and do research there.
The Institute is located below ground level in a behind-the-scenes secure section of the building. Above ground, visitors walking to and from the CTA bus stop in front of the planetarium, or to and from the adjacent parking lot, pass directly over it, completely unaware of what’s hidden one story below.
My role as a volunteer has been to record information found on a large collection of star charts and associated photographs the planetarium acquired several years ago.
That’s the short version.
A more specific description would be cataloging data associated with the Carte du Ciel, by far the planet’s largest science project of the late-19th and early-20th Centuries. International in scope and involving as many as 20 observatories on four continents working steadily over many years, the goal of the Carte du Ciel (“Map of the Sky”) was no less than to use the still-new medium of photography to accurately record the relative positions of millions of stars for the first time in human history, and then publish the results as The Astrographic Catalogue.
Each participating observatory was assigned a zone representing a specific part of the sky. Each was responsible for making and publishing its photographs and charts.
It was a revolutionary project in many respects, but the sheer volume of labor required to make the images, measure and plot the positions of every star of at least the 11th magnitude (brightness), and print and publish the results caused the project to run decades longer than expected. Most of the observations were made between 1895 and 1920, but one observatory worked on the project until 1948. Another was involved until 1950.
In the end, The Astrographic Catalogue (AC) was completed but not published in full until 1958. Subsequent enhanced versions appeared in the late 1990s.
An interesting part of Carte du Ciel history is the role women played in measuring the magnitude of stars captured in the photographs and charting their relative positions. In Europe and Australia, where the majority of participating observatories were located, women were routinely hired to do this early form of “computing,” an exacting and critically important task. (Readers wanting to learn more about women’s work in astronomy at the beginning of the 20th Century, including the Carte du Ciel, will appreciate Eva Isaksson’s “Not a Heavenly View." The title is telling.)
The Bus makes a stop at Carte du Ciel because, after working several weeks with charts created by just one of the participating institutions (the Observatoire de Bordeaux), I’m reminded of two axioms relevant to the extraterrestrial life debate and the search for life beyond Earth:
Science is usually incremental in approach and accomplishment.
Sustained efforts often produce unexpected results over time.
Over the course of the project’s lifetime, Carte du Ciel observatories recorded the relative positions of more than four million stars. This was a monumental accomplishment despite the errors that were sometimes made. But the effort also created a record against which star positions obtained through modern, more sophisticated techniques could be compared. And this enabled astronomers to more accurately determine the motions of the stars.
I suspect the dedicated women and men who spent years – and also careers – making all those images and charts had no idea their painstaking work would contribute in this way.
Kind of like not seeing the activity hidden below our feet.
Coming next: An astronomical xox
Banner bus photo created by Dorothy Delina Porter
