John Lester

John Lester

Ph.D. | Professor Emeritus | Astronomy
905 828 3818
905 828 5425
Office Location:
3359 Mississauga Road
Mississauga , Ontario
L5L 1C6


I study the physical processes that occur in the atmospheres of individual stars. Stellar atmospheres are often used as tools for the study of "macro" topics, such as the evolution of the Milky Way or the distance to other galaxies, and these applications interest me too. However, I am more intrigued by the astrophysics that takes place in the stellar atmosphere, which is an extremely complex boundary layer between the dense stellar interior and near vacuum of space. There are fundamental physical processes occurring in this environment that are still poorly understood because the size, temperatures, pressures, velocities and magnetic fields cannot be recreated in terrestrial laboratories. My approach to these problems is a combination of observation and computer modeling.

Courses Taught:

AST101H5, AST110H5, and AST201H5 (undergraduate)


Neilson, H. R., McNeil, J. T., Ignace, R and Lester, J. B., “Limb Darkening and Planetary Transits: Testing Center-to-limb Intensity Variations and Limb-darkening Directly from Model Stellar Atmospheres”, Astrophysical Journal, vol. 845, 12 pages, 2017 August 10.

Lester, J. B. Khatu, V. C. and Neilson, H. R., “Spectral Signatures of Stellar Mass in the Infrared H-Band” Publications of the Astronomical Society of the Pacific, vol. 129, page 024201, 7 pages, February 2017.

Neilson, H. R, Baron, F., Norris, R., Kloppenborg, B., and Lester, J. B.“Stellar Atmospheres, Atmospheric Extension and Fundamental Parameters: Weighing Stars Using the Stellar Mass Index”, Astrophysical Journal, vol. 830, Article 103, 6 pages, 20 October 2016.

Lester, J. B., “Book Review: The Life and Death of Stars by K. R. Lang”, The Journal of the American Association of Variables Star Observers, vol. 41, no. 2, page 379, November 2013.

Neilson, H. R. and Lester, J. B., “Spherically symmetric model stellar atmospheres and limb darkening. II. Limb-darkening laws, gravity darkening

coefficients and angular diameter corrections for FGK dwarf stars”, Astronomy & Astrophysics, vol. 556, Article A86, 8 pages, August 2013.

Neilson, H. R. and Lester, J. B., “Spherically-symmetric model stellar atmospheres and limb darkening. I. Limb-darkening laws, gravity darkening coefficients and angular diameter corrections for red giant stars”, Astronomy & Astrophysics, vol. 554, Article A98, 10 pages, June 2013.

Lester, J. B., Dinshaw, R. and Neilson, H. R., “Indicators of Mass in Spherical Stellar Atmospheres”, Publications of the Astronomical Society of the Pacific, vol. 125, 24 pages, 2013.

Neilson, H. R. and Lester, J. B., “Using limb darkening to measure fundamental parameters of stars”, Astronomy & Astrophysics, vol. 544Article 117, 7 pages, 2012.



B.A. - Northwestern University (1967)
M.S. - University of Chicago (1969)
Ph.D. - University of Chicago (1972)
Postdoctoral Research - Harvard-Smithsonian Center for Astrophysics (1972-76)