Angelo Secchi, the Jesuit father of astrophysics

It is a mark of genius to come up with questions that are obvious in retrospect but that nobody had ever thought of asking before. The Jesuit astronomer Angelo Secchi (pronounced “sekki”), whose 200th anniversary of birth is being celebrated this year, had that talent.

Before Secchi, astronomers were mainly interested in figuring out exactly where stars and planets were. This was important for navigation, and therefore commerce, and intricate mathematical systems were developed to track the motions of the heavens above in order to guide the motions of ships below. But Secchi asked a new question: What are stars and planets? With this question, the brand-new disciplines of astrophysics and planetary sciences were launched.


This may be Secchi’s most famous legacy; but taken in isolation, it does not do justice to his many talents and to a life full of discovery, invention, public service—and even political intrigue.

His was a life full of discovery, invention and public service.

Angelo Secchi was born into a large middle-class family in the northern Italian city of Reggio Emilia on June 28, 1818, and entered the Jesuit novitiate in Rome at the age of 15. His scientific abilities were recognized early on during his formation at the Roman College, the Jesuit university in Rome, and he studied under Francesco De Vico, S.J., director of the Roman College’s observatory, as well as Father Giovan Battista Pianciani, a Jesuit professor of physics and chemistry. By the time Secchi was working for his theology degree, he was moonlighting as Pianciani’s assistant.

Doubtless he would have continued on there in conventional research and teaching, but the winds of liberalism were blowing in Europe. In 1848, only months after Secchi was ordained a priest, Rome underwent a revolution, and the short-lived but strongly anticlerical Roman Republic was born. The Jesuits were forced to flee. Their father general, Jan Roothaan, donned a wig, disguised himself as a diocesan priest and repaired to a nearby port in a mail coach to sail for Sardinia. As for Secchi, he went to England and spent some time studying mathematics at Stonyhurst College before moving to Georgetown University in the United States.

Before Secchi, astronomers were mainly interested in figuring out exactly where stars and planets were. But Secchi asked a new question: What are stars and planets?

Secchi’s exile in the New World ended up being propitious, as he came into contact with leading scientists and a vigorous academic environment charged with the latest developments in astronomy and physics. When the Papal States were restored in 1849 and the Jesuits returned to Rome, he was appointed director of the observatory of the Roman College and took up his new job with all these new scientific ideas fresh in his mind. He began a major upgrade of the facilities and obtained a state-of-the-art telescope (German-engineered, of course). It was with this instrument that he conducted his most famous research into the nature of stars and planets. While he was not the first to realize it was possible to analyze what chemicals a glowing object is made out of by using a prism to spread its light into its constituent colors—a technique known as spectroscopy—he was the first to apply the technique systematically to objects in the heavens. He found he could group stars together according to common features in their spectra and came up with a stellar classification scheme that was widely adopted, and from which the modern-day system is ultimately derived.

One star claimed his particular attention: our own sun. In addition to studying its chemical composition through spectroscopy, he tracked variations in its brightness, figured out that there was a link between solar activity and changes in Earth’s magnetic field and did detailed studies of sunspots. In 1860 he was one of the first people to photograph the sun during an eclipse; and he was able to prove from his photographs that the sun’s corona, or outer atmosphere, was real and not just an optical illusion. His 1870 book Le Soleil (The Sun) is one of the most important works of solar science of the 19th century.

He also turned his attention to the planets, studying the composition of their atmospheres through spectroscopy. He made exact observations of Saturn’s rings and was among the first to study the surface details of Mars. He was a pioneer in photographing the moon and used the results to examine its craters in detail. In honor of his planetary research, an asteroid was named after him, as well as craters on the moon and on Mars.

Popularizer and Public Servant

What makes Secchi a fascinating figure is that his interests extended beyond what he could see through his telescope. His mind was seized by any new, interesting idea. For instance, when in 1851 Léon Foucault constructed a giant pendulum in Paris to demonstrate the earth’s daily rotation, Secchi replicated the experiment within a couple of months, suspending a 105-foot-long pendulum from the roof of the Church of St. Ignatius to show Romans the exciting new scientific result.

Ileana Chinnici, an astronomer in Palermo, Sicily, has recently completed Decoding the Stars: A Biography of Angelo Secchi, Jesuit and Scientist. When I asked her about Secchi’s interests, she characterized him as “a complete scientist,” who was enthusiastic about disseminating modern theories of physics not just among academics but more broadly among the public. “He was really an open-minded person,” she commented, “very attentive to new ideas and theories, very popular among all social classes. He liked to dialogue with everybody.” He gave public lectures about science, and his textbook On the Unity of the Physical Forces was an important instrument for disseminating the most modern ideas in physics within Italy.

Secchi designed and built an innovative meteorograph that tracked barometric pressure, temperature, wind velocity, humidity and rainfall.

His activity extended to very practical matters. It is easy to forget that even if its political constitution was at odds with Europe’s ascendant liberalism, the Papal States of the 19th century was a fully functioning, modern state. Secchi contributed much to its welfare, helping with the construction of electric railways, installing lightning rods on important buildings, coming up with a system for the lighthouses in the ports and ensuring drinking water was potable. He supervised a precise geodetic survey along the Appian Way that became the basis for accurate maps of the region.

But perhaps his most important civil contribution was in weather forecasting. He had already come into contact with the science of meteorology in the United States, and in 1856 he set up a daily telegraphic weather report for the Papal States, the first of its kind in Italy. Later he was invited by the Italian government (at the time outside of the Papal States) to set up its own such service. He designed and built an innovative meteorograph, or automatic weather recording device, that tracked barometric pressure, temperature, wind velocity, humidity and rainfall. It won the Grand Prix at the 1867 Universal Exposition in Paris, and Napoleon III awarded him the French Legion of Honor, while Peter II made him a grand dignitary of the Order of the Rose of Brazil.

Caught Up in Politics

In 1870 Rome was captured by the emerging Italian state, and Pope Pius IX retreated to the Vatican. The Roman College and its observatory were taken over by the new government, which immediately found itself in a bind. Angelo Secchi was clearly still the best man to head up the observatory, but as a Jesuit priest his loyalty to the pope was uncompromising. In the end, his scientific credentials and prestige won out. He was allowed to stay on as director of the observatory and was exempt from taking the oath of allegiance to the government.

But relations between Secchi and the new Italian state were not always smooth. In 1872 the Holy See named Secchi the pontifical delegate to an international meeting in Paris tasked with defining the length of a standard meter. The Italian scientists lodged an official protest, complaining that the Holy See was not a sovereign state and could not be represented as such at an international conference. They were overruled, and Secchi was warmly welcomed as a voting member of the proceedings.

The anticlerical sentiment of the 19th century continues to affect Secchi’s legacy today.

Secchi was never comfortable with the political situation; in the 1872 meeting he had been pressured into assuming the political role he did. While he was deeply worried that the liberal project would be a de-Christianizing force in Europe, he was also wary of the radical intransigence present in some quarters of the church. As Ms. Chinnici observes, he was attacked “both by anticlerical people and by ultraconservative Catholic people.” Thus, in a letter in 1877, Secchi lamented that “while some find skepticism and atheism in my writings, others see an exaltation of theology that undercuts physics in order to support the Bible.” Nor did it help, it should be added, that he had a “strong personality” (as Ms. Chinnici puts it) and occasionally came into personal conflict with other scientists.

The anticlerical sentiment of the 19th century continues to affect Secchi’s legacy today. In his hometown of Reggio Emilia, one can still see the house where he was born. Matteo Galaverni, a young priest of the diocese who has a doctorate in astronomy and is associated with the Vatican Observatory, used to pass this building with his father, himself an amateur astronomer, who would tell him stories about their city’s great son. Curiously, the commemorative plaque marking the home does not mention that Secchi was a Jesuit or a priest. Father Galaverni explained to me that this reflects the anticlericalism of the region, from which the Jesuits were expelled in 1859. Today, he says, many locals know him as a great astronomer, but few are aware that he was a priest.

Secchi remained a faithful Catholic and devoted Jesuit priest his whole life.

According to Guy Consolmagno, S.J., the current director of the Vatican Observatory, Secchi’s priesthood also harmed his reputation in the English-speaking world. “His rivals in the United Kingdom, including the founder and editor of Nature, Norman Lockyer, made certain that his works—even his popular works—were never translated into English,” Brother Consolmagno told me. “There were very successful versions published in French and German, but not English.” A contributing motive may have been that anglophone scientists were envious about how far ahead of them his work was.

Man of Science, Man of Faith

Though Secchi was accused of crypto-atheism, the fact is that he remained a faithful Catholic and devoted Jesuit priest his whole life. When he died in 1878, his will asked that his Legion of Honor medal be placed by the altar of St. Aloysius Gonzaga and his Order of the Rose by that of St. Ignatius Loyola, two great saints of the Society of Jesus buried in Rome.

But in what way did his science and his faith intersect? Brother Consolmagno considers him “typical of religious scientists of the 19th century. They still saw science, and physics in particular, as a source of unquestioning truth…. the crises of relativity and quantum theory were well in the future.” Nevertheless, even if his philosophy of science was somewhat naïve, he found no conflict between his work in the church and his work in the observatory—after all, the latter was literally built on top of the former. When Leo XIII wrote, a few years after Secchi’s death, that “truth cannot contradict truth,” he could very well have used Secchi as a real-life example of this principle.

Yet perhaps most important for us today—and especially for Christian scientists—was his conviction that scientists should not detach their research from their spiritual lives. “Even scientific intelligence,” he once wrote, “is one of the gifts of the Holy Spirit…. We ought to ask God for this gift when, in our studies, we place before ourselves the end that every Christian should set his sights on: not the vanity of surpassing those who have preceded us, nor arrogance or pride after having surpassed them, but rather let us, in our asking for intellectual light, seek only to understand the works of the Lord—to know his greatness and our duty.” As he saw it, the ultimate reason to pursue science was to know God better, “so that we can learn to love and serve him.”

True to his Jesuit charism, Angelo Secchi was a contemplative in action.

Comments are automatically closed two weeks after an article's initial publication. See our comments policy for more.
John Walton
5 months 4 weeks ago

Long those many decades ago there were many Jesuit scientists at my alma mater. There were men who had done trail-blazing in physics, biology, chemistry, entomology etc. Now there is but one. What's wrong with this picture?

John Kasbar
5 months 3 weeks ago

Thank you for this interesting and informative article. I share Secchi’s view of, and interest in, the relationship between science and Christianity. I look forward to reading the recent biography and learning more.

J Cosgrove
5 months 3 weeks ago

truth cannot contradict truth

There is nothing in science that contradicts a God nor Catholicism. It is a myth that science contradicts Christianity even though a lot of well educated people believe it does. Catholics should be aggressive in countering this false but popular myth. The truth is just the opposite,

Taylor Wilson
5 months 2 weeks ago

I have to Do My Dissertation upon theology degree but problem is that I have no information about it anyone can help me?


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