Ethan Tecumseh Vishniac (born 1955) is an American astrophysicist. He is the son of microbiologist Wolf V. Vishniac, and grandson of photographer Roman Vishniac. He is the Editor-in-Chief of the Astrophysical Journal and a professor of Astronomy at Johns Hopkins University in Baltimore, after holding positions at University of Saskatchewan in Saskatoon, McMaster University in Hamilton, Ontario, Canada, and University of Texas in Austin. His wife Ilene Busch-Vishniac, the ninth president of the University of Saskatchewan (2012-2014), was previously Dean of the Faculty of Engineering at Johns Hopkins, and provost and vice-president (academic) of McMaster University from 2007 until 2012.
His best known scientific work is the study of instabilities in expanding blast waves. In Vishniac (1983), he demonstrated that a blast wave expanding in a sufficiently compressible medium would be subject to a linear overstability growing as the square root of time. This is usually known as the Vishniac instability, and generally occurs in any thin enough slab bounded by a shock on one side and a contact discontinuity to a higher temperature region on the other. In Vishniac (1994) he then demonstrated that a thin-enough slab bounded by shocks on both sides is subject to a nonlinear instability, usually described as a nonlinear thin shell instability (NTSI). He has also worked with success in cosmology and the theory of astrophysical dynamos.
- Vishniac, E. T. 1983, Astrophys. J., 274, 152
- Vishniac, E. T. 1994, Astrophys. J., 428, 186