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Much of Wendy Freedman's work has focused on a growing problem: the expansion of the universe. As one of three principal investigators on the Hubble Space Telescope Key Project, Freedman measured the Hubble constant, which describes the rate of the universe's expansion. The constant is an important tool for determining the age of the universe, its early structure, the amount of dark matter it contains, and answers to many other questions in astronomy, physics, and cosmology. Recently, Freedman has examined supernovae—super-bright exploded stars—probing the universe's past expansion and the nature of dark energy, the mysterious force that accounts for two-thirds of the universe's density. Additionally, Freedman has a long-standing interest in the evolution of galaxies, particularly the study of their stellar populations and the nearby universe. Freedman earned her Ph.D. in astronomy and astrophysics from the University of Toronto in 1984. She is the Director and Crawford H. Greenewalt Chair of the Carnegie Observatories in Pasadena, Calif. In 1987, she became the first woman appointed to the Carnegie’s permanent scientific staff.
Listen to the Interview (requires free RealPlayer software):
Freedman discusses how an early interest in science -- and a formative high-school physics class -- led to her the University of Toronto, first as a biophysics student, then as an astronomy major. Her early work centered on star formation; a serendipitous block of telescope time at Hawaii's Mauna Kea Observatories and rapidly improving technology led her to explore galaxies outside the Milky Way using Cepheids, stars whose changing luminosity can be used to measure distances between objects in space. This work led to the Hubble Space Telescope Key Project, which used Cepheid stars to measure the universe's expansion. (9 minutes)
Freedman discusses Edwin Hubble’s work at Mount Wilson, where he found Cepheids within nebulae, which helped prove the existence of other galaxies similar to the Milky Way. Not long after Einstein published his general theory of relativity, Hubble discovered the universe was expanding; both discoveries laid groundwork for the later big-bang theory of the universe’s origin. Freedman talks about her work determining the Hubble constant, which measures the rate at which the universe is expanding. The constant was tough to measure accurately until the launch of the Hubble Telescope in 1990, which allowed astronomers to view the universe free of the distortion caused by Earth’s atmosphere. (8 minutes)
Freedman delves into the implications of an expanding universe. Big-bang theory does not specify a rate of expansion, the amount of matter in the universe, or confirm the existence of dark energy or a cosmological constant; answers will come only through observation and experimentation. Freedman explains the importance of staying current with others' work, because seemingly unrelated, parallel research often combines in ways that challenge accepted theories. Measurements of supernovae movements and cosmic microwave background radiation, for example, both suggest that just one-third of the universe's density is visible matter, while two-thirds are mysterious "dark energy." (11 minutes)
Freedman talks about the beginnings of the Hubble Key Project, put on hold when the Hubble Telescope’s launch was delayed after the space shuttle Challenger exploded. In retrospect, she feels the delay gave computers and other technology a chance to improve and handle the amount of data the project produced. After measuring distances to 24 galaxies between 1994 and 1999, the researchers published their final result in 2001. (8 minutes)
Now that the Hubble Key Project is finished, Freedman has switched her focus to observing the behavior of supernovae, exploded super-bright stars. Her research group is examining supernovae at high and low red-shifts, in part to avoid the distortion caused by dust and variable composition of Cepheid stars. They will use the Carnegie Observatories’ new telescopes in Chile, which are equipped with infrared detectors, and characterize how the universe’s rate of expansion is changing over time. (8 minutes)
Freedman talks about the next major space telescope which will measure infrared radiation with a mirror larger than that of the Hubble Telescope. The James Webb Space Telescope will help scientists study the early universe and star formation, complementing data already collected by Hubble. Ultimately, however, Freedman thinks another Hubble-type, ultraviolet- and optical-sensitive telescope must be built to provide the resolution needed for observing supernovae. Freedman segues into a discussion of the universe's early evolution, explaining the inflation model and its relation to current science. She discusses her plans for the next generation of instrumentation at the Carnegie Observatories, which she directs. (9 minutes)
Freedman discusses women’s long history in astronomy, especially as compared to other sciences. She talks about the shift from the lone astronomer sitting alone at the telescope to the more recent team approach, pioneered by projects like the Hubble Key. Finally, Freedman discusses her plans for the future and her wishlist of technological improvements for her field. (7 minutes)
Last Updated: 10-18-2004
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The audio files linked above are part of the National Academy of Sciences InterViews series. Opinions and statements included in these audio files are those of the interviewee and do not necessarily reflect the views of the National Academy of Sciences.