Finding the unexpected in vast pulsar data sets
A PhD project beginning September 2025
Overview
A PhD position is an opportunity to direct your enthusiasm and creativity into ground-breaking research, with support to develop the skills you need to become a leader in your field. In this project, you will push the boundaries of our understanding of extreme neutron star physics, developing your own research ideas and building expertise in AI and large-scale data science. You will apply machine-learning and data science techniques to discover anomalies in vast data sets of radio pulsar observations, and use these to understand how neutron stars evolve over their lifetimes.
Project summary
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Pulsars, spinning neutron stars emitting a beam of radio waves, are some of the most extreme objects in the Universe, yet the physics of how they are powered remains a mystery. The best chance of advancing understanding is to find ordinary pulsars behaving in unexpected ways. In this project, you will have access to over a million radio pulses from a thousand pulsars observed with MeerKAT, the most sensitive radio telescope in the Southern hemisphere. With so many observations to study, we need to take an AI-centred approach to handle the influx of new information. You will apply novel visualizations, statistics and unsupervised machine-learning to discover the cases where pulsars behave strangely, and work with an international team of experts to investigate the causes of this behaviour. You will then use these discoveries to make connections across the whole population of radio transients, from incredibly fast-spinning millisecond pulsars, to extragalactic Fast Radio Bursts.
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The MeerKAT telescope. Photo taken December 2017
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Scientific context
What are pulsars?
Pulsars are neutron stars: incredibly dense objects with mass just bigger than the Sun and radii of only 10 km. Radio pulsars emit a bright beam of radio waves that acts like the beam of a lighthouse, with the beam sweeping through space as neutron star spins. This means the radio emission appears to us on Earth as a series of pulses: one from each rotation of the star. We study these pulses across time, looking at the spin period and its variability; radio frequency; brightness; pulse shape; and polarization properties. These give us clues about the intense magnetic fields and plasma interactions taking place in the magnetosphere, revealing the origins of these stars and how they evolve over their lifetimes.
What do we learn from them?
Understanding the physics of pulsar radio emission is crucial for pushing the boundaries of modern physics. In addition to being some of the most extreme environments in the Universe, pulsars can be used as tools to probe fundamental physics and galactic structure. Pulsars spin so regularly that they can be used as clocks out in space. This means it is possible to test the theory of General Relativity and search for gravitational waves by timing the arrivals of pulses. The radio beam from a pulsar can be used as a torch that shines through and illuminates the invisible structures of the galaxy, that is, the gas, dust and plasma that make up the interstellar medium (ISM). By measuring the impact of the ISM on the radio emission we observe, we can even map out the magnetic field of the Milky Way. However, being able to use pulsars as precision tools in this way relies on our understanding how they work, and there are still many unanswered questions to address.
What problems do we need to solve?
Current models of pulsar physics are being pushed to breaking point by new discoveries. Examples include strange polarization behaviour, unexpected sudden changes, and unfathomably slow-spinning sources. On top of that, we know that pulsar timing (for finding gravitational waves) is limited by unexplained intrinsic variability in pulse arrivals. The bright flashes from other galaxies, known as Fast Radio Bursts (FRBs), may originate from a particularly extreme type of pulsar called a magnetar, but we do not yet understand the mechanisms relating ordinary pulsars to magnetars, and magnetars to FRBs. The best opportunities to discover the holes in our physical models, and to make connections across the pulsar population, are likely to come from ordinary pulsars behaving in unexpected ways. We know current models don't explain everything, but can we find examples of idiosyncratic behaviour that can only be explained by a particular physical scenario?
How will this project address these problems?
We have collected a very large data set of pulsar observations with the Thousand-Pulsar-Array, a survey on the South African MeerKAT radio telescope. We know that the data set is full of variability on short and medium timescales that is reasonably predictable, such as drifting, timing variability and profile changes, but we do not yet know how often unexpected or unpredictable behaviour take place, such as mode-changing, extreme scattering events, or completely unexpected phenomena. By searching for the anomalies in these observations, we can pin down their origins and advance our understanding of extreme and fundamental physics.
Pulsars are neutron stars: incredibly dense objects with mass just bigger than the Sun and radii of only 10 km. Radio pulsars emit a bright beam of radio waves that acts like the beam of a lighthouse, with the beam sweeping through space as neutron star spins. This means the radio emission appears to us on Earth as a series of pulses: one from each rotation of the star. We study these pulses across time, looking at the spin period and its variability; radio frequency; brightness; pulse shape; and polarization properties. These give us clues about the intense magnetic fields and plasma interactions taking place in the magnetosphere, revealing the origins of these stars and how they evolve over their lifetimes.
What do we learn from them?
Understanding the physics of pulsar radio emission is crucial for pushing the boundaries of modern physics. In addition to being some of the most extreme environments in the Universe, pulsars can be used as tools to probe fundamental physics and galactic structure. Pulsars spin so regularly that they can be used as clocks out in space. This means it is possible to test the theory of General Relativity and search for gravitational waves by timing the arrivals of pulses. The radio beam from a pulsar can be used as a torch that shines through and illuminates the invisible structures of the galaxy, that is, the gas, dust and plasma that make up the interstellar medium (ISM). By measuring the impact of the ISM on the radio emission we observe, we can even map out the magnetic field of the Milky Way. However, being able to use pulsars as precision tools in this way relies on our understanding how they work, and there are still many unanswered questions to address.
What problems do we need to solve?
Current models of pulsar physics are being pushed to breaking point by new discoveries. Examples include strange polarization behaviour, unexpected sudden changes, and unfathomably slow-spinning sources. On top of that, we know that pulsar timing (for finding gravitational waves) is limited by unexplained intrinsic variability in pulse arrivals. The bright flashes from other galaxies, known as Fast Radio Bursts (FRBs), may originate from a particularly extreme type of pulsar called a magnetar, but we do not yet understand the mechanisms relating ordinary pulsars to magnetars, and magnetars to FRBs. The best opportunities to discover the holes in our physical models, and to make connections across the pulsar population, are likely to come from ordinary pulsars behaving in unexpected ways. We know current models don't explain everything, but can we find examples of idiosyncratic behaviour that can only be explained by a particular physical scenario?
How will this project address these problems?
We have collected a very large data set of pulsar observations with the Thousand-Pulsar-Array, a survey on the South African MeerKAT radio telescope. We know that the data set is full of variability on short and medium timescales that is reasonably predictable, such as drifting, timing variability and profile changes, but we do not yet know how often unexpected or unpredictable behaviour take place, such as mode-changing, extreme scattering events, or completely unexpected phenomena. By searching for the anomalies in these observations, we can pin down their origins and advance our understanding of extreme and fundamental physics.
Objectives
- Develop new machine-learning techniques to search for the anomalies and corner cases in vast pulsar data sets.
- Connect these discoveries to neutron star physics: find the holes in existing models of the pulsar magnetosphere.
- Explain how anomalous events affect pulsar timing and the search for gravitational waves.
- Investigate the link with FRBs: can Giant Pulses and other anomalous events tell us anything about the origins of these extreme extragalactic bursts?
What skills will you develop?
Completing a PhD is a chance to fully immerse yourself in academic research and spend focused time answering the questions that you find the most exciting and important. It is also a fantastic opportunity to develop your skills in communicating ideas, managing projects, and interacting with a global research community. You will develop a wide array of key technical skills, including developing software; programming in Python; statistical techniques; and a strong grounding in data science and machine-learning.
What opportunities and support can you expect?
- The opportunity to take ownership of your own research and become a leader of projects and publications.
- A schedule of weekly supervisor meetings to help guide your development.
- Membership of international collaborations with two of the world’s best radio telescopes: Murriyang and MeerKAT.
- The chance to work with experts from across the world, particularly the UK, Germany, South Africa and Australia.
- A network of mentors both within pulsar science and at the University of Southampton.
- Training: in data science and machine-learning; in Python programming and software development; in managing very large data sets; and in key communication skills.
- Opportunities to present your research at national and international conferences.
- A collaborative research trip to Australia.
What qualifications and previous experience do you need?
You will need a very good undergraduate degree: at least a UK 2:1 honours degree or its international equivalent. A Physics degree is desirable, but if you hold a degree from another scientific discipline, and can demonstrate aptitude and enthusiasm for computational data analysis, then you are also very welcome to apply. You should be able to demonstrate some prior experience with computer programming, ideally in Python.
Funding information
There is internal funding available for UK/EU students. If you are an international student, take a look at the webpage linked below for more information about potential funding opportunities, and get in touch if you have any questions.
How to apply
Full details of how to apply are available on the Southampton Astronomy Group PhD webpage: www.astro.soton.ac.uk/postgrad.html
Get in touch by email if you have any questions!
Get in touch by email if you have any questions!
