Carnegie Observatories Director John Mulchaey and Carnegie Embryology Director Yixian Zheng serve jointly as interim Co-Presidents of Carnegie following the retirement of Matthew Scott. During this period, Mulchaey and Zheng will continue in their directorship roles at their respective departments.

John Mulchaey investigates groups and clusters of galaxies, elliptical galaxies, dark matter—the invisible material that makes up most of the universe—active galaxies and black holes. He is also actively involved in public outreach and education.

Most galaxies including our own Milky Way exist in collections known as groups, which are the most common galaxy systems and are important laboratories for studying galaxy formation and evolution. Mulchaey studies galaxy groups to understand the processes that affect most galaxies during their lifetimes.

Mulchaey received his B.S. in astrophysics from UC-Berkeley and his Ph. D. from the University of Maryland. He was a fellow at the Space Telescope Science Institute and at Carnegie before joining the Carnegie staff.

Yixian Zheng’s lab has a long-standing interest in cell division. In recent years, their findings have broadened their research using animal models, to include the study of stem cells, genome organization, and lineage specification—how stem cells differentiate into their final cell forms. They use a wide range of tools, including genetics in different model organisms, cell culture, biochemistry, proteomics, and genomics.

Zheng was a Howard Hughes Medical Investigator from 2000 to 2012. She studied biology as an undergraduate in China before moving to Ohio State University where she received a PhD in 1992. She was a postdoctoral fellow at the University of California, San Francisco from 1992 to 1996, when she moved to Carnegie as a staff scientist.