Phil Armitage, astronomy

WELCOME to the web site of Phil Armitage. I'm an astrophysicist interested in using numerical simulations to understand the physics of protoplanetary disks, the formation of extrasolar planets, and the astrophysics of black holes. Topics of recent interest incude the physics of protoplanetary and circumplanetary disks, the role of magnetic fields in black hole accretion, and the formation of seed supermassive black holes in quasistars. I have a joint appointment at Stony Brook University, where I am a Professor in the Department of Physics and Astronomy, and at the Center for Computational Astrophysics at the Flatiron Institute, where I am a Senior Research Scientist.

Visualization of a simulation of the Vertical Shear Instability

Predicting the observational appearance of protoplanetary disks in which the Vertical Shear Instability is active, including live dust coagulation physics (lead: Thomas Pfeil)

Recent papers
Just a Phase? Weakening Vertical Shear Instability explains Class II disk morphologies: Simulations with dust coagulation, sedimentation, thermal relaxation, and backreaction, T. Pfeil, A. Ziampras, S. Zhang, P.J. Armitage, & Y.-F. Jiang, ApJL, in press

On the formation of retrograde S-type planets in binaries with a polar circumbinary disk, C. Chen, P.J. Armitage, C.J. Nixon, S.H. Lubow, & R.G. Martin, ApJL, in press

A framework to model stellar irradiated disks with frequency-dependent absorption and scattering opacities in Athena++, S. Baronett, Y.-F. Jiang, Z. Zhu, S. Zhang, P.J. Armitage, ApJ, submitted

exoALMA XXIII. Estimating disk and planet properties from dust morphologies with DBNets2.0, A. Ruzza, et al., ApJL (2026)

On the orbital evolution of binaries with polar circumbinary disks, C. Chen, P.J. Armitage, & C.J. Nixon, ApJL (2026)

Pulsational instability of quasi-stars: Interpreting the variability of Little Red Dots, M. Cantiello, J.B. Hassan, R. Perna, P.J. Armitage, M.C. Begelman, Y.-F. Jiang, T. Ryu, & R.H.D. Townsend, ApJL (2026)

The astrometric resoeccentric degeneracy: Eccentric single planets mimic 2:1 resonant planet pairs in astrometry, D.A. Yahalomi, T. Lu, P.J. Armitage, M. Bedell, A.R. Casey, A.M. Price-Whelan, & M. Rice, ApJL (2026)

The growth of the central black holes in quasi-stars, J. Hassan, R. Perna, M. Cantiello, P.J. Armitage, M.C. Begelman, & T. Ryu, ApJ (2026)

Magnetic pressure dominance stabilizes AGN disks against gravitational instability, H.J. Gerling-Dunsmore, M.C. Begelman, J.B. Simon, & P.J. Armitage, ApJ (2026)

Reviews and notes
Planet formation theory: an overview (Armitage, introduction for the 2nd edition of the Handbook of Exoplanets)

Demographics of young stars and their protoplanetary disks (C.F. Manara et al., review for Protostars and Planets VII)

Lecture notes on accretion disk physics (arXiv only)

Visualizing the kinematics of planet formation, Disk Dynamics Collaboration

Physical processes in protoplanetary disks (Armitage, 45th Saas-Fee Advanced Course "From Protoplanetary Disks to Planet Formation")

Dynamics of protoplanetary disks (Armitage, ARA&A, 2011)

Lecture notes on the formation and early evolution of planetary systems (arXiv only)

Textbook

Personal I did my undergraduate and graduate work at the University of Cambridge, working with Cathie Clarke at the Institute of Astronomy as my primary advisor. I was a postdoc at CITA and MPA, a lecturer at St Andrews, and a professor at the University of Colorado (2002-2018) before moving to New York.

Beyond work I enjoy hiking, often combined with photography. My main focus is landscapes, but over the years I've also made trips to photograph bears in some spectacular spots in Alaska.