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Emma L. Alexander

Astrophysics PhD student working within radio astronomy and polarimetry, with a particular interest in radio galaxies. Communicating science, especially astronomy, through a variety of outreach (presentations, demonstrations) and media (television, podcasting, and radio).


Images of the Moon taken on successive nights in May 2020 from Manchester, UK. Camera: Sony DSC-HX60V.
Unedited single frames.



Emma Alexander
Jodrell Bank Centre for Astrophysics
University of Manchester
M13 9PL

emma.alexander (at)


Research interests


I am in my final year of my PhD, supervised by Dr Paddy Leahy and Prof. Anna Scaife, with my project titled "Magnetic fields around Radio Galaxies". Primarily, I work on POSSUM, the Polarisation Sky Survey of the Universe's Magnetism. POSSUM is one of the Science Surveys currently being carried out by ASKAP, the Australian Square Kilometre Array Pathfinder telescope. Another ASKAP project I have contributed to is and EMU, the Evolutionary Map of the Universe.

Magnetic fields

POSSUM makes use of a physical phenomenon called Faraday Rotation. Radio waves can be polarised; this means that the waves only oscillate (or "wiggle") in a particular direction. If a polarised radio wave passes through a magneteoionised medium (i.e. a part of space with free electrons and magnetic fields), its polarisation angle changes. By measuring how this polarisation angle changes with radio frequency, we can study the Universe's magentic fields.

I am also involved in another astrophysical magnetism study, QUOCKA. QUOCKA uses the Australia Telescope Compact Array to make complimentary observations to POSSUM.

Radio galaxies

My research focuses on radio galaxies in particular. They're pretty much exactly what they say on the tin: galaxies which are bright in the radio part of the light spectrum.All of the galaxies that I study have an Active Galactic Nucleus, or AGN. AGN occur when black holes at the centre of galaxies convert the mass that they consume into energy, which they release as powerful jets. These jets can stretch out to distances much larger than the galaxies themselves, and are bright when seen in radio waves, especially when these beams spread out into more diffuse 'lobes' as they encounter material in the space between galaxies.

Link: University of Manchester research profile.


Image of an ASKAP dish (source).

Faraday rotation

Diagram of Faraday rotation (source)

Hercules A

Multiwavlength view of radio galaxy Hercules A. (Source, Credit: NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)


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