Since its founding in 1891, many people have passed through the doors of the Vatican Observatory. A quick perusal of our guestbook reveals several Names, including Popes, nobel laureates, astronauts, actors, and saints.
Today's guestbook entry is from March 20, 1911, when P. H. Cowell made a visit.
He was superintendent of the H.M. Nautical Almanac Office, part of the Royal Greenwich Observatory, from 1910-1930.
As an astronomer, he was particularly dedicated to celestial mechanics, computing and refining the orbits of many comets and other solar system bodies. He developed a method for computing perturbations in an orbit that proved to be both relatively simple and robust. He is known for refining the orbit of the moon and resolving a discrepancy between its observed orbit and its theoretical orbit.
He also showed that the supposed perturbations of the orbit of Neptune--that suggested the existence of an undiscovered planet beyond its orbit--were erroneous and disappeared when all effects were accounted for. (Ironically, the search for the nonexistent "Planet X" did coincidentally result in the discovery of Pluto.)
He discovered the asteroid 4358 Lynn.
The asteroid 1898 Cowell is named for him.