James Gunn (astronomer)

James Gunn (born October 21, 1938) is an American astrophysicist. He is a professor emeritus of astrophysical sciences at Princeton University. Gunn's research has significantly impacted cosmology and observational astronomy.

Gunn is best known for his theoretical and observational contributions to the understanding of galaxy formation, large-scale structure in the universe, and the intergalactic medium. He has made key contributions to the development of cosmological models, including the cold dark matter model.

His theoretical work includes the Gunn-Peterson trough, a prediction of the absorption of light from distant quasars by neutral hydrogen in the intergalactic medium. This prediction, and its subsequent observational confirmation, provided crucial evidence for the reionization epoch in the early universe.

Gunn has also been heavily involved in the design and construction of astronomical instruments. He played a leading role in the Sloan Digital Sky Survey (SDSS), overseeing the design and construction of the survey's special-purpose 2.5-meter telescope and its instruments. He also contributed significantly to the software and data reduction pipelines used by the SDSS. He has also been involved in other major astronomical projects, including the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and the Dark Energy Spectroscopic Instrument (DESI).

His awards and honors include the National Medal of Science (2009), the Gruber Cosmology Prize (2005), and the Crafoord Prize in Astronomy (2023).