In 1985, the UA Theoretical Astrophysics Program (TAP) was created based on the shared vision of Jack (Randy) Jokipii and the then-heads of the astronomy, physics, and planetary sciences departments. The aim was to combine evident faculty and departmental strengths to create a theoretical program that would complement the UA’s recognized strengths in observational astronomy and planetary sciences. Since its inception, the State of Arizona has continued to provide annual funding which has supported the development of this tightly integrated program and increased the growth and visibility of the UA’s leadership in the area of theoretical astrophysics.


The Departments of Astronomy, Physics, and Planetary Sciences form the Theoretical Astrophysics Program along with key partnerships with Applied Mathematics and the National Optical Astronomy Observatory (NOAO). Membership is open to all UA faculty, research partners, postdocs, and grad students interested in the field of theoretical astrophysics. Several TAP faculty affiliate members are also recognized members of the National Academy of Science: David Arnett, Randy Jokipii, and Renu Malhotra.

Each year, the TAP offers colloquia covering a broad range of current research topics given by early-career scholars as well as senior faculty. TAP also awards the Graduate Student Research Prize to one UA grad student or recent Ph.D. with the winning submission selected for research quality and originality. The TAP Small Grants Program provides limited funding to TAP members to support research-related travel expenses, equipment purchase, research dissemination, etc.

TAP Steering Committee

The TAP is directed by a Steering Committee composed of six members and a chairperson with member representation equally distributed across the departments of physics, astronomy, and planetary sciences. The steering committee is responsible for making significant program decisions, including program funding priorities and allocations, selection of student prize recipient, new member applications, and general planning of annual program priorities and directions.

Gurtina Besla, Interim Chair

Associate Professor, Steward Observatory

Dr. Gurtina Besla’s research focuses on the formation and evolution of low mass dwarf galaxies. Through numerical simulations, Dr. Besla explores the impact of gravitational interactions on the observed properties of low mass galaxies in various environments. Dr. Besla is a world expert in the study of the closest example of an interacting pair of dwarf galaxies, the Large and Small Magellanic Clouds. Dr. Besla’s research on these galaxies has overturned conventional wisdom, illustrating that the Magellanic Clouds are likely recent interlopers in our neighborhood rather than long term companions to our Galaxy.

Federico Fraschetti

Research Scientist, Lunar and Planetary Laboratory

Dr. Fraschetti specializes the problem of acceleration and transport of charge particles in turbulent media, namely origin of cosmic-rays. His interests span space physics, high energy astrophysics, and laboratory astrophysics (project/interpretation of experiments to study the generation of collisionless shock waves). Recent interest in the effect of charged particles accelerated by young stars on the evolution of proto-planetary disks and on the evolution of life in exo-planets.

Sam Gralla

Associate Professor, Physics

Dr. Gralla works on the theory of strong gravitational and electromagnetic fields, as occur near black holes and neutron stars.  While most of his research is astrophysically motivated, he also ventures into more theoretical territory like black hole thermodynamics.

Kristopher Klein

Assistant Professor, Lunar and Planetary Laboratory

Dr. Klein’s research focuses on studying fundamental plasma phenomena that governs the dynamics of systems within our heliosphere as well as more distant astrophysical bodies. He has particular interest in identifying heating and energization mechanisms in turbulent plasmas, such as the Sun’s extended atmosphere known as the solar wind, as well as evaluating the effects of the departure from local thermodynamic equilibrium on nearly collisionless plasmas which are ubiquitous in space environments.

Shufang Su

Professor of Physics, Department of Physics

Fields of Study: Astrophysics and Cosmology and High Energy Physics

Research Interests: Theoretical elementary particle physics focusing on new physics beyond Standard Model. Phenomenology of new physics models, collider searches, Higgs physics, electroweak precision studies, dark matter and particle cosmology.

Andrew Youdin

Associate Professor – Astronomer, Steward Observatory

Dr. Youdin is a theoretical astrophysicist whose primary focus is the formation and evolution of planetary systems. He employs various techniques, including analytic derivations, statistical data analysis and detailed numerical simulations. Current research topics include planetesimal formation, giant planet formation, exoplanet statistics and atmospheres, circumbinary dynamics, and accretion disks. His work on the streaming instability, a mechanism to concentrate planet-forming solids in disks, has transformed the modern understanding of planetesimal formation. Dr. Youdin investigates a range of planet formation mechanisms with an eye to ongoing breakthroughs in exoplanet, disk and Solar System observations.


Rosie Johnson

Project Manager
Steward Observatory, Room N334A


Nicole Divine

Office Specialist
Steward Observatory, Room N334