John B. “Jack” Rogerson, Jr. (1922–2021)

John Rogerson, Jr. passed away on Thursday, July 8, 2021, at the age of 99.

John Rogerson, Jr., was Professor Emeritus in the Department of Astrophysical Sciences at Princeton University. Jack (as he was universally known) was active at Princeton in the heyday of the department’s involvement in space-based astronomy, playing a key role first in the Stratoscope project to fly a series of telescopes on balloons to get above the turbulence of the Earth’s atmosphere, and later in the Copernicus satellite, at the time the largest telescope to be launched into space, to study the ultraviolet spectra of massive stars and the nature of the interstellar medium.

Rogerson was born on September 3, 1922, in Cleveland and came to Princeton to do his graduate studies. He finished his Ph.D. in 1954 and, after a brief stint as a Carnegie Fellow at Mt. Wilson Observatories in Pasadena, he returned to Princeton in 1956 as a researcher. He was promoted to the faculty in 1963. Working closely with Professor Martin Schwarzschild, he played a critical role in the construction and flights (starting in 1957) of the first Stratoscope, a 12-inch telescope launched on a balloon to an altitude of 16 miles. Without the distorting effects of the Earth’s atmosphere, Stratoscope-I obtained the highest-resolution images to date of the surface of the Sun, which demonstrated the phenomenon of solar granulation in the form of convection cells in the hot gas in the solar photosphere.

Another benefit of sending a telescope into space is that one can make astronomical observations at ultraviolet wavelengths, which otherwise are absorbed by the Earth’s atmosphere. Rogerson and Lyman Spitzer worked together on developing a space-borne 32-inch telescope, initially dubbed “Orbital Astronomical Observatory-3” to exploit this scientific opportunity. OAO-3 was launched on August 21, 1972 and carried out scientific observations from its Earth-circling orbit until it was decommissioned in 1981. Its launch coincided with the 500^th anniversary of the birth of Nicolas Copernicus, and it was subsequently renamed “Copernicus” after the launch. Rogerson carried out detailed spectroscopic studies of hot stars with Copernicus, publishing a series of influential stellar spectroscopic atlases and constraining among other things the rate at which mass was lost from these stars in the form of stellar winds.

In the 1970’s, Rogerson and his collaborator Don York used Copernicus data to make the first measurements of the abundance of deuterium in the interstellar medium. Deuterium is an isotope of hydrogen, which was produced in trace amounts in the first few minutes after the Big Bang. The relative amounts of deuterium and hydrogen is a sensitive probe of conditions in those first few minutes of the universe; Rogerson and York’s measurements were the first of a series that have led to one of the cornerstones of our modern cosmological model, accurately constraining the density of ordinary (baryonic) matter in the universe.

Rogerson was a quiet and private person who loved music, reading and travel. Those who knew him describe him as extremely kind. He was married to Elizabeth M. (Betty) Rogerson, née Van Doren, who passed away in 2012. Jack Rogerson retired in 1988, moving to Pennswood in Pennsylvania, and his involvement with the department and with Princeton University largely ended at that time.

Written with input from Don York and Don Morton.