Bruce Partridge has been a part of the European Space Agency's Planck satellite project for a quarter of a century. The emeritus professor of astronomy's advice was sought early on in the planning process for the space observatory that was designed to make unprecedentedly detailed maps of the Cosmic Microwave Background (CMB) radiation—the heat left over from the Big Bang. He helped write the proposals that secured its funding, led the subgroup that planned and analyzed its data on the present universe of stars and galaxies, and spent years writing and editing the many scientific publications that emerged from the mission. In recognition of that work, Partridge, as a member of a team of 40 international scientists, was awarded the 2018 Gruber Prize alongside principal investigators Jean-Loup Puget and Nazzareno Mandolesi.

"Of course, it is a huge honor for us," says Partridge, who retired in 2008 after 38 years on the Haverford faculty. "It is especially nice that the Gruber Foundation recognized the team. Planck has truly been a team effort, involving hundreds of individuals from at least ten countries. It is unusual for prizes like this to be awarded to teams rather than individual scientists, but the Gruber Foundation was willing to make an exception for Planck."

“The Planck project has made definitive measurements of the properties of our expanding universe," said University of Arizona's Robert Kennicutt, who was chair of the Selection Advisory Board to the Prize. "This stunning achievement was the result of a large group effort, and we are pleased to recognize both the Planck team as a whole and its principal science team leaders.”

The Planck project was started in 1993, and the spacecraft was in orbit collecting data from 2009 to 2013. It provided a new census of the universe (29.4 percent dark matter, 65.7 percent dark energy, and 4.9 percent "ordinary" matter), found robust evidence that the geometry of the universe is "flat," and measured the CMB's subtle palette of temperature differences, to name just a few of its achievements. Its data provided virtually irrefutable evidence in support of the standard model of the universe on the smallest to the largest scales.

Partridge, the only U.S.-based member of the team from a liberal arts college, has been involved in more than 70 publications resulting from Planck, and at least a half dozen Haverford students have made "substantial contributions to the mission," including co-authoring related publications.

"One alum, Ben Walter '13, a classics major, helped polish the clarity of a foot-high stack of Planck papers," said Partridge. "Another example is the use of Planck observations to calibrate ground-based radio telescopes—at least three recent grads and current student, Gerrit Farren ’20, have been or are involved in that project. The students and I have sharpened the precision of the largest radio telescope in the U.S., and are set to do the same for the billion-dollar-plus Atacama Large Millimeter Array in Chile."

The Gruber Prize was awarded on August 20, at the General Assembly of the International Astronomical Union, in Vienna, Austria. The three recipients—Mandolesi, Puget, and the team—divided the $500,000 annual award, and each principal investigator also received a gold medal.

Post-Planck, Partridge has become more involved in a ground-based experiment located in northern Chile, the Atacama Cosmology Telescope, which seeks to complement Planck’s observations of the CMB, but at finer scale and higher sensitivity. Obviously, his 50-plus years studying the CMB were of prime importance to his award-winning contributions, but the cosmologist also gave credit to his experience working on international teams and his "admittedly meagre" language skills in his success with the Planck team and beyond.

"The working language of [Planck] was English, but it sure helped to be able to chat after work or tell a joke in my partners’ languages," he said. "Science students who fret at [Haverford's] language requirement, take note!"