Mapping with the stars: Nuns instrumental in Vatican celestial survey

IMAGE: CNS/courtesy Vatican Observatory

By Carol Glatz

CITY (CNS) — Of the many momentous or menial tasks women religious perform,
one of the better-kept secrets has been the role of four Sisters of the Holy
Child Mary who were part of a global effort to make a complete map and
catalog of the starry skies.

until recently, the women were no more than nameless nuns whose image has long
been preserved in a black and white photograph that showed them wearing
impeccably ironed habits and leaning over special microscopes and a ledger.

now their identities have been pulled out of obscurity by Jesuit Father Sabino
Maffeo, assistant to the director of the Vatican Observatory. He stumbled onto
their names as he was going through the observatory archives, “putting
papers in order,” he told Catholic News Service April 26.

Emilia Ponzoni, Regina Colombo, Concetta Finardi and Luigia Panceri, all born
in the late 1800s and from the northern Lombardy region near Milan, helped map
and catalog nearly half a million stars for the Vatican’s part in an
international survey of the night sky.

astronomers from around the world met in Paris in 1887 and again in 1889 to
coordinate the creation of a photographic “Celestial Map”
(“Carte du Ciel”) and an “astrographic” catalog pinpointing the stars’ positions.

astronomer and meteorologist, Barnabite Father Francesco Denza, easily convinced
Pope Leo XIII to let the Holy See take part in the initiative, which assigned
participating observatories a specific slice of the sky to photograph, map and

Maffeo, an expert in the observatory’s history and its archivist, said Pope Leo
saw the Vatican’s participation as a way to show the world that “the
church supported science” and “was not just concerned with theology
and religion.”

Vatican was one of about 18 observatories that spent the next several decades
taking thousands of glass-plate photographs with their telescopes and
cataloging data for the massive project.

the project at the Vatican Observatory began to suffer after Father Denza died
in 1894.

Pope Pius X found out the new director wasn’t up to the job, he called on
Archbishop Pietro Maffi of Pisa to reorganize the observatory and search for
the best replacement, Father Maffeo said.

1906, the archbishop found his man at Georgetown University in Washington D.C.
— Jesuit Father John Hagen who had been heading its observatory there since
1888 and was renowned for his research on “variable” stars, which
have fluctuating brightness.

he had extensive experience in astronomy, Father Hagen never did the kind of
measurements and number crunching required for the astrographic catalog,
Father Maffeo said.

he went to Europe to see how they did it and saw that in some observatories
there were women who read the (star) positions and wrote them in a book with
precise coordinates,” the 93-year-old Jesuit priest said.

astronomers told Father Hagen that once the young women “were shown how to
do it, they were very diligent,” Father Maffeo said. At the Royal
Observatory in Greenwich, for example, they even were referred to as “lady
computers” because of the skill needed to calculate the coordinates
according to set formulae.

Father Hagen wondered where he might be able to hire young women for the
Vatican, “he immediately thought — nuns,” and contacted the Sisters
of the Holy Child Mary, who were located nearby, Father Maffeo said.
Coincidentally, Mary is often symbolized in Catholic Church tradition by a

a letter dated July 13, 1909, to the superior general, Mother Angela Ghezzi,
Archbishop Maffi said the Vatican Observatory “needs two sisters with
normal vision, patience and a predisposition for methodical and mechanical

Maffeo said the sisters’ general council was not enthused “about wasting
two nuns on a job that had nothing to do with charity.” However, Mother
Ghezzi was “used to seeing God’s will in every request,” he said, and
she let two sisters go to the observatory.

for the sisters began in 1910, but soon required a third and later a fourth nun
to join the team. Two would sit in front of a microscope mounted on an inclined
plane with a light shining under the plate-glass photograph of one section of
the night sky.

plates were overlaid with numbered grids and the sisters would measure and read
out loud each star’s location on two axes and another would register the
coordinates in a ledger. They would also check enlarged versions of the images
on paper.

Vatican was one of about 10 observatories to complete its assigned slice of the
sky. From 1910 to 1921, the nuns surveyed the brightness and positions of
481,215 stars off of hundreds of glass plates.

painstaking work did not go unnoticed at the time. Pope Benedict XV received
them in a private audience in 1920 and gave them a gold chalice, Father Maffeo
said. Pope Pius XI also received the “measuring nuns” eight years
later, awarding them a silver medal.

Vatican’s astrographic catalog, which totaled 10 volumes, gave special
mention to the sisters, noting their “alacrity and diligence,”
uninterrupted labors and “zeal greater than any eulogy” could express
at a task “so foreign to their mission.”

international project to catalog star positions and build a celestial map
ended in 1966 and recorded nearly 5 million stars. The catalog consists of
more than 200 volumes produced by 20 observatories and the unfinished map is
made up of hundreds of sheets of paper — all work culled from more than 22,000
glass photographic plates of the sky.

Maffeo said, “Never before had there been a presentation of the stars as
vast as this.”

the project was quickly eclipsed by huge technological developments in
surveying stars, modern-day scientists eventually discovered that comparing the
star positions recorded a century earlier with current satellite positions
provided valuable information about star motions for millions of stars.

project showed that even in a new era of satellites and software, quaint
glass-plate photographs and “lady computers” weren’t wholly obsolete.


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