William Van Dyke Dixon

As branch manager of MESA, the Mission Engineering and Science Analysis Branch within the Instruments Division, Dr. Dixon leads a cross-mission, cross-instrument group that fosters coordination among instrument teams and communication between scientists and engineers. MESA supports the Hubble Space Telescope (HST), the James Webb Space Telescope (JWST), and the Nancy Grace Roman Space Telescope missions. Branch members serve as technical editors, develop software, and lead various working groups. MESA includes the Operations Detector Lab (ODL), which works to understand the behavior of the electronic detectors used on all of the missions supported by the Institute.

As an instrument scientist for the JWST Near-Infrared Imager and Slitless Spectrograph (NIRISS), Dr. Dixon led the effort to simulate and reduce wide-field slitless spectroscopic data, and he chaired the JWST Pipeline Working Group. As an instrument scientist for Hubble’s Space Telescope Imaging Spectrograph (STIS) and Cosmic Origins Spectrograph (COS), he worked on calibration, troubleshooting, and user support. As an instrument scientist for Hubble’s Wide-Field Planetary Camera 2 (WFPC2), he led the effort to recalibrate the entire WFPC2 archive before the instrument was decommissioned.

Earlier in his career, Dr. Dixon served as a research scientist at the Johns Hopkins University, where he led development of the data-reduction pipeline for the Far Ultraviolet Spectroscopic Explorer (FUSE). As a post-doc at the Space Sciences Laboratory, U.C. Berkeley, he was responsible for mission planning during the ORFEUS II mission and reduction of Berkeley Spectrometer data from both ORFEUS I and II. As a graduate student at the Johns Hopkins University, he was involved in mission planning for the Hopkins Ultraviolet Telescope (HUT) during both the Astro-1 and 2 space-shuttle missions.

Dr. Dixon has a deep commitment to advancing diversity, equity, and inclusion in astronomy.  He chaired the American Astronomical Society's Committee for Sexual-Orientation and Gender Minorities in Astronomy (SGMA) from its founding (as the Working Group on LGBTIQ Equality) in January of 2012 until June of 2017, for which he was named a Legacy Fellow of the American Astronomical Society in 2020.  He served on the organizing committee for the Women in Astronomy IV conference in June of 2017 and on the science organizing committee for the Inclusive Astronomy 2 conference in October of 2019.  He is a member of the American Astronomical Society, the American Physical Society, the International Astronomical Union, the Astronomical Society of the Pacific, and the International Dark-Sky Association.

Education:

PhD in Physics and Astronomy, Johns Hopkins University
MA in Physics and Astronomy, Johns Hopkins University
BSPA in Physics and Astronomy, University of Georgia
BS in Mathematics, University of Georgia

Science Interests:

Dr. Dixon's scientific interests center on the study of UV-bright stars in globular clusters. These objects represent a brief (10,000 to 100,000 year) phase of stellar evolution, during which stars move across the HR diagram, either from the asymptotic giant branch (AGB) or directly from the extreme horizontal branch (EHB) to the start of the white-dwarf cooling curve. By measuring their effective temperature, luminosity, and mass, we can constrain theories of stellar evolution. By measuring their chemical abundances, we can better understand the nucleosynthetic processes at work in the atmospheres of AGB stars, which remain poorly understood. Stars in globular clusters offer the added benefit of known distance, age, and initial composition.

• Abundances, atmospheres, and evolution of UV-bright stars in globular clusters
• Dust and hot gas in the interstellar medium
• Identification and classification of brown dwarfs and cool stars from low-resolution spectroscopy

Research Topics: Star Formation, Histories, and Evolution; Interstellar Medium; Star Clusters; Astrochemistry, Chemical Abundances

ORCID ID: 0000-0001-9184-4716