ABSTRACT

The Hubble constant, H_o, provides a measure of the current expansion rate of the universe. In recent decades, there has been a huge increase in the accuracy with which extragalactic distances, and hence H_o, can be measured. While the historical factor-of-two uncertainty in H_o has been resolved, a new discrepancy has arisen between the values of H_o measured in the local universe and that estimated from cosmic microwave background measurements, assuming a Lambda cold dark matter model. I will review the advances that have led to the increase in accuracy in measurements of H_o, as well as describe exciting future prospects with JWST and Gaia, which will make it feasible to measure extragalactic distances at percent level accuracy in the next decade.

About the Speaker:

Wendy L. Freedman is best known for her measurement of the Hubble Constant. She is now the John & Marion Sullivan University Professor of Astronomy and Astrophysics at The University of Chicago. Her principal research interests are in observational cosmology, focusing on measuring both the current and past expansion rates of the universe, and on characterizing the nature of dark energy.

Freedman is an elected member of the National Academy of Sciences and the American Philosophical Society, and an elected Fellow of the American Academy of Arts and Sciences and of the American Physical Society. She has received numerous awards and honors for her contributions to observational cosmology, including a Centennial Lectureship of the American Physical Society (1999), the John P. McGovern Award in Science (2000), the Magellanic Premium Award of the American Philosophical Society (2002) and the Marc Aaronson Lectureship and prize (1994). In 2009 Freedman was one of three co-recipients of the Gruber Cosmology Prize, widely considered to be astronomy’s equivalent of the Nobel Prize. Professor Freedman received the 2016 Dannie Heineman Prize for Astrophysics, awarded jointly by the American Institute of Physics and the American Astronomical Society.