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Wendy Freedman has made a career of measuring the universe. Her efforts to refine the Hubble constant — a value that represents the expansion rate of the universe — helped deepen our understanding of the age and scale of the cosmos.
Freedman, who is currently the John & Marion Sullivan University Professor of Astronomy and Astrophysics at the University of Chicago, gained the tools and knowledge she needed to launch her career during her time at U of T.
“My U of T education prepared me for many of the projects and roles I’ve taken on throughout my career,” says Freedman, a three-time alum.
Freedman completed a bachelor of science in 1979 as a member of University College before earning a master of science in 1980 and a doctorate in 1984, both at the Department of Astronomy & Astrophysics. U of T conferred an honorary doctor of science upon Freedman at a convocation ceremony in 2013.
“It’s a magnificent university,” Freedman says. “Students starting out there really have a leg up in terms of their career prospects.”
Freedman, long recognized for her important contributions to science, continues to accrue major accolades. Last year, she was honoured with the National Medal of Science — presented by then-President Joe Biden — and more recently received the 2026 Benjamin Franklin Medal in Physics.
“These moments come out of the blue,” Freedman says. “It’s nice to get this recognition, but the real reward is doing science.”
Just how old is the universe?
As an observational cosmologist, Freedman studies fundamental aspects of the universe using telescopes, both Earth-based and in space. From 2003 to 2014, she was the director of Carnegie Observatories and has overseen many high-profile projects throughout her career.
One of Freedman’s greatest scientific contributions was leading a project that determined a more accurate value of the Hubble constant.
In the 1990s, Freedman co-led a team of astronomers on the Hubble Space Telescope Key Project. The group measured the distance to particular types of stars, called Cepheids, in other galaxies. These Cepheids fluctuate in brightness — a characteristic astronomers use to help infer distance, speed of expansion and even the age of the universe.
The result of the Key Project was a newly refined Hubble constant of approximately 73 kilometres per second per megaparsec — a distance of 3.26 million light years — which placed the universe at 13.5 billion years old.
“The Hubble constant is the most important parameter in cosmology simply because it sets both the size scale and the time scale of the universe as it’s evolving,” Freedman says. “It’s been notoriously difficult to measure.”
That difficulty manifested when researchers later measured the cosmic microwave background — the radiation left over from the Big Bang — and found a different Hubble constant: 67.
“The question before us now is: Is this difference between 67 and 73 telling us something fundamental about the universe that is missing from the standard cosmological model?” Freedman asks.
To that end, Freedman’s work continues. Her research group is refining techniques and using the James Webb Space Telescope to observe and measure Cepheids and supernovae.
“I’m optimistic that in the next four or five years, we will really get to the bottom of this,” she says. “I think this is a solvable problem.”
Returning to her roots
Last October, Freedman returned to U of T and delivered a colloquium for U of T’s astronomy community.
“U of T still feels like home,” she says. “I spent some of the most enjoyable years of my life there.”
Freedman says the department had a collegial culture and her professors set her up for success by supporting her work. She was encouraged to attend conferences that gave her important exposure to others in the field at a formative stage in her career.
“Graduate studies at U of T really set me in the right direction,” she says. “I don’t know what would have happened if I’d gone anywhere else.”
Freedman’s connection to the university runs even deeper than being a three-time graduate. She grew up in Toronto and still has family here. Many of her family members are also U of T graduates, including her father, grandfather, sister and brother.
She met her husband, Barry Madore, at U of T. Madore also completed a master of science and doctorate at the Department of Astronomy & Astrophysics, in 1971 and 1974 respectively. He is currently an academic researcher at Carnegie Institution for Science.
“We started out as colleagues and ended up forging a life together,” Freedman says. “Marriage and family. A long marriage: more than 40 years now.”
Freedman says she’s fortunate to share scientific interests with her partner and to have children who understand the demands of her job.
“These careers are not nine to five,” Freedman says. “Having such a supportive family is a huge element in allowing me to have the career I’ve had.”