Australian Dictionary of Biography

Daniel Joseph Kelly O’Connell (1896-1982), Jesuit priest, astronomer and seismologist, was born on 25 July 1896 at Rugby, England, one of four children of Irish-born Daniel O’Connell (d.1905), Inland Revenue officer, and his English wife Rosa Susannah Helena, née Kelly (d.1907). Soon after the death of his mother, Daniel was sent to Clongowes Wood College, Dublin. At 17 he joined the Society of Jesus at Tullabeg and in 1915 entered his juniorate at Rathfarnham Castle. He majored in experimental physics and mathematics at University College, Dublin (B.Sc., 1919; M.Sc., 1920; D.Sc., 1949, National University of Ireland). Subsequently he studied philosophy at St Ignatius’ College, Valkenburg, the Netherlands, where he began watching variable stars, especially eclipsing binaries that were to become the main focus of his astronomical research.

O’Connell planned to attend the University of Cambridge but, due to a lung condition, he was advised to leave Britain. In 1922 he arrived at St Ignatius’ College, Riverview, Sydney; he did his regency, taught physics and the next year became assistant-director at the college’s observatory. He returned to Ireland in 1926 to complete his theological studies at Milltown Park, Dublin. Ordained on 31 July 1928, he undertook his tertianship at St Bueno’s College, Wales. In 1931 he travelled to Cambridge, Massachusetts, United States of America, to study at the Harvard College Observatory with Harlow Shapley.

Back at Riverview Observatory in 1933, O’Connell became director in 1938. At the observatory his research included seismology and the measurement of time with various kinds of clocks, as well as astronomy in the field of variable stars using the newly developed technique of photographic photometry. In 1935 he was elected a fellow of the Royal Astronomical Society and a member of the Royal Society of New South Wales; he served on the RSNSW council (1946-49) and as vice-president (1950-52), and became an honorary member in 1953. He was chairman from 1946 of the board of visitors of Sydney Observatory. One of the friendships he established while in Australia was with (Sir) Richard Woolley, director of Mount Stromlo Observatory. O’Connell presented radio talks, including a series of three titled ‘According to Hoyle’ on the Australian Broadcasting Commission station 2BL-2NC in March and April 1952.

That year O’Connell was called to Rome as director of the Vatican Observatory. On 26 July he left Australia, arriving in time for the Rome meeting of the International Astronomical Union. He continued his work on eclipsing binary stars, again using photoelectric photometry. A leading expert in the field, he was president (1955-61) of the commission on photometric double stars of the IAU. He published The Green Flash and Other Low Sun Phenomena (1958), which included colour photographs proving that the phenomenon, sometimes seen at sunrise or sunset, was real and not subjective.

At the Vatican Observatory O’Connell built up the staff and installed a 60/90-cm Schmidt telescope that became the observatory’s largest instrument. As objective prisms were available, the telescope was used for spectroscopy. With leading scientists he organised two study weeks—one on stellar populations in 1957 and another on nuclei of galaxies in 1970—and published the proceedings. He had personal friendships with three popes, especially Pope Pius XII. In 1970 he retired from his observatory post but continued as president (1968-72) of the Pontifical Academy of Sciences.

O’Connell died on 14 October 1982 at the headquarters of the Society of Jesus in Rome. He is remembered mainly for his work on eclipsing binary stars and the ‘O’Connell effect’ that relates to the rotation of the major axis of the elliptical orbit of a double star.