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I grew up in the little fishing town of Kilkeel in County Down, at the foot of the Mourne Mountains.  I read Natural Sciences at Christ’s College, Cambridge, followed by a Ph.D. in astrophysics at the Cavendish Laboratory. After postdoctoral positions as a Research Astronomer at the Royal Greenwich Observatory, and then as a PPARC Research Fellow back at the Cavendish, I came to Oxford as a departmental lecturer in physics in 2003.  I also held a college lectureship in physics at St Peter’s, and then I came to Exeter, where I am now a Tutorial Fellow and Professor of Physics, in 2015.


My research centres on high-energy astrophysics, particularly in the relativistic jets and very-high-energy particles created in extreme environments such as accreting black holes and supernova blast waves.  In my research group we study these phenomena at all wavelengths from radio through to the highest-energy gamma rays.  The group works on both theory and experiment: we are members of the largest ground-based experiment in gamma-ray astronomy, the High-Energy Stereoscopic System (H.E.S.S.) in the Khomas highlands in Namibia, and we work on the development of the next generation ground-based observatory for gamma-ray astronomy, the Cherenkov Telescope Array (CTA). We are currently spending much of our time perfecting the cameras for some 40 four-meter telescopes for CTA that will be constructed in the Atacama Desert in northern Chile over the next few years.

We are quite a fun “Jack of all trades” group where on one flank we engage with the physics of black holes and relativistic particles, and on the other with applications of our experimental technology, in fields such as medical imaging. We are also engaged in several human capacity building projects in Namibia, using astronomy as a vehicle for development in education and in the tourism industry.

All of it is very exciting and the group is always eager to recruit new graduate students.


As a member of a family that has been full of teachers for many generations, I recognise that it is a great privilege to have the opportunity to teach at a university like Oxford (and especially at a college like Exeter where we place particular emphasis on the teaching role of our Fellowship). At Exeter I teach the first-year papers Mechanics & Relativity and Electromagnetism, second year Quantum Physics, and third year Particle and Nuclear Physics and General Relativity.

In the Department of Physics, I am Associate Head of Department and Head of Graduate Education.

Selected Publications

The feasibility of magnetic reconnection powered blazar flares from synchrotron self-Compton emission Morris, Paul J., Potter, William J., Cotter, Garret, Monthly Notices of the Royal Astronomical Society, 486, 1584, 2019.

Gamma-ray novae: rare or nearby? Morris, Paul J.; Cotter, Garret; Brown, Anthony M. Chadwick, Paula M., Monthly Notices of the Royal Astronomical Society, 465,1218, 2017.

New constraints on the structure and dynamics of black hole jets Potter, William J.; Cotter, Garret, Monthly Notices of the Royal Astronomical Society, 453, 4070, 2015.

Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence Hallinan, G.; Littlefair, S. P.; Cotter, G. et al., Nature, 523,568, 2015.

The First Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope, Abdo, A.A., et al., The Astrophysical Journal, 715,429, 2010.


Seeing across the galaxy

Media Coverage

For the first time ever, scientists spot an aurora outside our solar system, Washington Post