WILLIAMSTOWN -- Jay Pasachoff, Field Memorial Professor of Astronomy at Williams College, was in Paris on Saturday, Sept. 7, to receive the Prix-Jules-Janssen (the Jules Janssen Prize) awarded to him in 2012 from the Societe Astronomique de France, "for outstanding research, teaching and popularisation of Astronomy, in the spirit with which Camille Flammarion created the award back in 1897."
The preceding evening, Pasachoff lectured on his recent research, including discussions of his work with Williams College colleagues and students on solar eclipses, occultations of distant stars by Pluto and other objects in the outer solar system, and transits of Venus across the face of the sun.
The lecture was held in the 340-year-old building of the Paris Observatory, in the Salle de Cassini with the meridian of Paris dividing the room's width in half. While in Paris, he also gave a formal colloquium at l'Observatoire on his transit-of-Venus research on Monday morning, Sept. 9.
The Societe Astronomique de France is an organization that undertakes educational outreach in astronomy, and was founded by the astronomer Camille Flammarion, a noted popularizer of astronomy, in 1887. Pasachoff joined the society's officers at the home-museum of Flammarion in a Paris suburb after the prize ceremony.
The Prix-Jules-Janssen, named after the French astronomer who discovered in 1868 that the solar chromosphere was gaseous and, while commenting on that gas, was one of the first two or three people to discover helium, was founded in 1897.
Among past recipients of the Janssen prize were Samuel Pierpont Langley in 1898, Percival Lowell in 1904, George Ellery Hale in 1917, Albert A. Michelson (who, with Williams College alumnus E.W. Morley discovered that the speed of light did not vary when measured with or perpendicular to the direction of the Earth's motion), Arthur Eddington in 1928, Albert Einstein in 1931, Jean-Claude Pecker (who spent a sabbatical year at Williams College) in 1967, Evry Schatzman in 1973 and others, for all but one year since 1897.
Pasachoff, while an undergraduate at Harvard, spent the summer after his sophomore year (1961) in Paris to work with Schatzman and Pecker, arranged by his Harvard tutor, David Layzer. Pasachoff has worked with French scientists including Serge Koutchmy of l'Institut d'Astrophysique and Zadig Mouradian of l'Observatore de Paris Meudon on solar studies as far back as the total solar eclipse of 1970 in Mexico. In the 1970s and ‘80s, he observed interstellar deuterium with Diego Cesarsky, who later worked at l'Institut d'Astrophysique, on studies of interstellar deuterium with cosmological consequences, and he collaborated with l'Institut d'Astrophysique's Alfred Vidal-Madjar on the distribution of such gas in our galaxy. During the past year, Vidal-Madjar was part of a team including Pasachoff that used the Hubble Space Telescope to observe a transit of Venus in reflection off Jupiter's clouds. Pasachoff now works with Thomas Widemann of l'Observatoire de Paris-Meudon on studies of the atmosphere of Venus, most recently at the June 2012 transit; Widemann and Bruno Sicardy of l'Observatoire are in a group containing Pasachoff, Bryce Babcock of Williams College, and their students in studying Pluto and other objects in the outer solar system through their occultation of distant stars.
Pasachoff's recent research is being supported by the Committee for Research and Exploration of National Geographic Society, the Planetary Astronomy Program of NASA, and the Solar Terrestrial Program of the Atmospheric and Geosciences Division of the National Science Foundation, in addition to NASA through the Space Telescope Science Institute for the Hubble studies.
Passachoff came to Williams College in 1972 as the sole astronomer, assistant professor of astronomy and director of the Hopkins Observatory, the nation's oldest extant astronomical observatory. His sabbatical leaves have been at the University of Hawaii, l'Institut d'Astrophysique, the Institute for Advanced Study in Princeton, the Harvard College Observatory and Caltech.