May 21, 2015 7:22 p.m. ET
When he was 19, Piazzi joined the Theatine Order of clerics, which supported his doctoral studies in philosophy and mathematics. At 34, he was asked to occupy the chair of higher mathematics in Palermo. Palermo had climatic conditions favorable for astronomical observations, and Piazzi decided to found an observatory there, the southernmost in Europe. He traveled to England to obtain the most accurate telescope then available. With its help he developed a catalog of almost 7,000 stars, the most extensive and accurate up to that time. L’Institut de France awarded it the prize for “best astronomical work published in 1803.”
Piazzi’s entry into history began on January 1, 1801, when he noticed a faint “star” not contained in any catalog. Tracking it over the following nights, he found that it moved across the background stars the same way planets do. After more than 40 nights, however, it moved too close to the sun to be seen. Would it ever be found again, once it emerged from the sun’s glare?
That would require the difficult feat of computing its orbit precisely from the positions Piazzi had measured. This was accomplished by the great mathematician Carl Friedrich Gauss, and Piazzi’s object was located again by a German observatory exactly a year after its original discovery. In 1802, Piazzi named it Ceres after the patron goddess of Sicily.
But what was it? Was it a planet? It moved like one, and didn’t have the characteristics of a comet. The picture was clouded, however, by the finding in short order of three more objects with similar orbits: Pallas (1802), Juno (1804), and Vesta (1807). It turned out that Piazzi had found the first of many thousands of “asteroids” or “minor planets” whose orbits lie mainly in a belt between Mars and Jupiter. Ceres is the largest asteroid, large enough that its gravity squeezes it into a sphere, like a planet and unlike other asteroids. Hence its recent reclassification as a “dwarf planet.”
Most news accounts don’t mention that Piazzi was a Catholic priest. In fact, the remarkable story of the Catholic clergy’s contributions to science is one of the best-kept secrets of scientific history. The exception is Gregor Mendel; it is widely known that the science of genetics began with the experiments of the Austrian monk.
But it is the rare person who knows that the big-bang theory, the central pillar of modern cosmology, was the brainchild of the Belgian Catholic priest and physicist Georges Lemaître. In the 1920s, Lemaître showed that Albert Einstein’s equations of gravity allow space itself to expand and, connecting this to observations that distant galaxies were flying apart, he formulated his famous theory of how the universe began.
The Jesuits have an especially rich scientific tradition. In the 16th century, the Jesuit astronomer Christopher Clavius developed our modern calendar. In the 17th century, Jesuit Giambattista Riccioli mapped the moon, and Christoph Scheiner helped discover sunspots. Francesco Grimaldi discovered the enormously important physics effect called “diffraction,” the effects of which you can see in the colorful bands of a glimmering CD. In the 19th century, the Jesuit Angelo Secchi, a founder of astrophysics, pioneered the study of the sun and stars using the spectra of their light and developed the first spectral classification of stars, the basis of the one now used.
But Jesuits don’t have all the glory. Blessed Niels Stensen (1638-86) made major contributions to anatomy, especially of the glandular-lymphatic system, and, even more impressively, helped found the science of geology by developing the correct theory of sedimentary rock, geological strata and the origin of fossils, which unlocked Earth’s history. Marin Mersenne (1588-1648), of the Minimite Order, made fundamental discoveries about sound. The work of the Abbé Lazzaro Spallanzani, one of the top biologists of the 18th century, is taught in high-school textbooks today.
Ask a Catholic audience whose name they associate with the Catholic Church and science. “Galileo!” they shout. Ask them about Lemaître, Grimaldi, Stensen, Secchi—or Piazzi—and you get blank stares. Is it any wonder the science-religion warfare myth persists?
Messrs. Barr and Mullan are professors of physics at the University of Delaware. Mr. Barr is the author of “Modern Physics and Ancient Faith” (Notre Dame, 2006).