The story of the Vatican’s “calculating” nuns who filled the sky with stars

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This story originally appeared in The Conversation

The story of the Vatican’s “calculating” nuns who filled the sky with stars
The story of the Vatican’s “calculating” nuns who filled the sky with stars

From Marta Macho-Stadler, University of the Basque Country / Euskal Herriko Unibertsitatea

The Carte du Ciel -he Sky map– It was an international astronomical project that started at the end of the 19th century. Attempts have been made to map and identify the astronomical coordinates of millions of stars in the celestial sphere in order to reach those with apparent sizes 11 and 12.

The project began in 1887 under the auspices of the Paris Observatory, which at the time was headed by Amédée Mouchez, one of the first to recognize the potential of photographic techniques in the field of star mapping (astrophotography). The project was abandoned in 1970 without being able to complete it. Even so, the release of the Hipparco’s catalog (ESA, 1997) reused some of this historical photographic material.

Mouchez fitted the Paris Observatory with a double equatorial mount, fitted with a telescope consisting of a photographic lens 33 cm in diameter and a visual lens 19 cm in diameter. He envisioned a project in which 22,000 photographs – on photo plates – would be taken of the entire sky. He joined his project with a number of large observatories from around the world, although not all succeeded in completing their mission. Each of them was assigned a different part of the sky, which had to be photographed with an instrument identical to that in Paris.

The work was carried out simultaneously in two steps. In the first case, the positions of several reference stars had to be precisely delimited. The positions of the other observed stars were derived from them.

In the second stage the photographic images were generated. These were supplied to “pocket calculators” trained to infer the position of the stars on each plate in relation to the coordinates of the reference stars contained on that plate. At the time, the term “calculator” referred to the people who were employed to perform these calculations. mechanics. In most cases it was women. This system was used to calculate the correct ascent and declination of each observed star.

The equatorial coordinates: ascent and descent to the right. Image: Francisco Javier Blanco González.
The equatorial coordinates: ascent and descent to the right. Image: Francisco Javier Blanco González. Wikimedia Commons

The “pocket calculator” of the Vatican

In most cases the name of these astronomical “calculators” is unknown. you are simple computers trained to do arduous mechanical work, but very accomplished diligent. They observed the position of the stars using the photographic material made available to them and calculated the exact coordinates of these stars. This work, which is assessed as ancillary activity, can be carried out a priori by anyone without prior training. But without them, without the “calculators”, this gigantic project, like so many others, could not be carried out.

In 2016, the Jesuit Sabino Maffeo – archivist and assistant to the director of the Vatican Observatory – accidentally and among some forgotten documents discovered the identities of the female computistas of the Vatican Observatory: Emilia Ponzoni, Regina Colombo, Concetta Finardi and Luigia Panceri, four sisters of the Order of Maria Bambina, a community that lived near the observatory.

The Vatican Observatory was involved in the project Carte du Ciel Thanks to the astronomer and meteorologist Francesco Denza, the Pope Leo XIII. convinced of the company’s interest. Leo XIII. Agree to participate in the project, in part to quell allegations of Church opposition to science.

After the deaths of Denza and Leo XIII, the project suffered. Pope Pius X found that the work of the observatory was not working properly and asked the Archbishop of Pisa, Pietro Maffi, to reorganize it. In 1906, the Jesuit Johann Hagen, who had headed the Georgetown University observatory since 1888 and was a student of variable stars, was appointed director of the Vatican Observatory. Hagen visited other European observatories and found that in some of them women were responsible for observing the photographic plates and recording the exact coordinates of the stars.

After listening to Hagen’s explanations, Pietro Maffi believed that this work of calculating the star positions could be done by nuns. In July 1909 the Archbishop of Pisa sent a letter to the Superior of the Order of Maria BambinaAngela Ghezzi. In this letter Maffi noted that “he needed two sisters with normal eyesight, patience and a disposition for methodical and mechanical work”.

In 1910, two nuns began working with the observatory, despite initial concerns from the community who felt that this mandate was too far removed from their mission of charity. Due to the volume of work to be done, a third and later a fourth was added.

Between 1910 and 1921 and with the help of microscopes to observe the photo plates, the four sisters determined the position and luminosity of 481,215 stars as part of the project Carte du Ciel.

In gratitude for her meticulous work, Pope Benedict XV received. In 1920 they were adorned in front of a private audience, and eight years later Pope Pius XI decorated them. You with a silver medal.

But then they were forgotten.

There will be those who think it is not too important to name the women who are meticulously watching, calculating and cataloging in the photo that opens this letter. In my opinion, they certainly deserve to appear in the history of astronomy: without their devotion to the incomplete catalog Carte du Ciel it would have had a lot fewer stars.The conversation

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