Physicist Persis Drell, director of the Stanford Linear Accelerator Center, will discuss “What We Know (and What We Don’t Know!) about the Night Sky" Sept. 15, 5:30 p.m. in Jepson Hall, Room 120.

Drell is an expert in particle physics and was one of Discover magazine’s top 50 women in science in 2002.

Drell received bachelor’s degrees in mathematics and physics from Wellesley College and a doctorate in atomic physics from the University of California, Berkeley. She is the sister of University of Richmond medieval and renaissance historian Joanna Drell.

Drell’s talk is free and open to the public. For more information, call the physics department at 804-289-8783.