PhD Programme

Armagh Observatory is known world-over as a leader in the field of astronomical research; we welcome PhD Candidates every year. Applications for starting in Oct 2022 will soon be open.

Support our PhD Programme

PhD Application Information

Applications will soon be invited for a 3.5 year postgraduate research studentship(s) tenable at Armagh Observatory & Planetarium from Oct 2022. Armagh Observatory, located in Northern Ireland, UK, is an astrophysical research institute founded in 1789.

It has 8 staff astronomers, 4 post-doctoral fellows, 12 PhD students and several visiting astronomers. Research interests include Solar Physics, Solar-System Science, Stellar, Galactic and Extra-galactic Astrophysics. A number of potential PhD projects on these topics is available for perspective candidates to consider in their application.

Candidates must have, or expect to obtain, at least an upper second class honours degree or equivalent, in an appropriate discipline (e.g. Physics, Mathematics, Astronomy or Astrophysics). Successful candidates will enrol at an appropriate university and carry out a research programme at the Armagh Observatory & Planetarium. Applications are encouraged from candidates of any nationality although eligibility may depend on funding source. The successful applicant(s) would receive a grant based on the United Kingdom Science and Technology Facilities Council rate (2021/22: 15,609 per annum). In addition, we would fully fund the university fees.

Current Research Projects

Time Domain Astrophysics - Supervisor: Gavin Ramsay

As one famous astronomer once said, if you monitor the brightness of a star with sufficient precision for a sufficiently long time, every star is ‘variable’. I have been studying variable stars for many years and use the brightness information to investigate the properties of accretion discs around compact binary systems; how flare originate on low mass stars; how frequent are flares from solar-type stars; search for activity cycles on stars and identify new explosive ‘transient’ sources from survey data.

A number of potential science projects are available but are expected to partly use data from the Gravitational-wave Optical Transient Observer (GOTO). This survey is an international project which Armagh is a founder partner and aims to detect the optical counterpart of gravitational wave events detected by the Advanced Ligo and Virgo detectors. Other projects could use data from the TESS satellite which is currently surveying the entire sky and providing a unique opportunity to study stellar variability.

These projects would suit someone interested in observational astronomy and ideally someone with experience of computing languages. It is expected there would be opportunities for travelling to La Palma, Australia or South Africa to help commission new GOTO nodes or help make detailed observations of objects discovered in these surveys.

For further information contact: gavin.ramsay@armagh.ac.uk

Magnetic Fields of Degenerate Stars - Supervisor: Stefano Bagnulo

White dwarfs (WDs) are the end point of 90% of stellar evolution. 15–20% of such stars possess strong magnetic fields. The fields range over five dex in strength, from below ten kG (one Tesla) up to about 1000 MG. The fields are roughly dipolar, and show no evidence of rapid secular changes. They seem to be “fossil fields”, produced in earlier evolution that evolve slowly by ohmic decay. At present, there is no single firmly established theoretical scenario that explains how prior evolution through the red giant and AGB phases can leave strong surface fossil magnetic fields in a significant fraction of WDs. Possibilities include retaining fields from earlier evolutionary phases, or field generation during binary mergers.

Using various facilities at the Very Large Telescope, at the Canada-France-Hawaii Telescope, and at the William Heschel Telescope, Armagh astronomers are performing a large survey of magnetic WDs in the vicinity of our solar system, with the goal to understand if and how magnetic fields evolve with time, and if they are correlated to other features of the stellar atmospheric chemistry, mass, and age. A PhD project is offered to help to obtain observational constraints that will be used to understand the origin of magnetic fields in WDs.

The student will learn how to use spectro-polarimetric techniques to detected and model stellar magnetic fields. She or he will help with the preparation of proposal for telescope time, with the execution and analysis of the observations, with the search for correlation between magnetic fields and other stellar parameters, and with the modelling of time series of polarised spectra and of surface magnetic field structure of of WDs. The project will be more theoretically or observationally oriented according to the preference and skills of the student.

For further information contact stefano.bagnulo@armagh.ac.uk

Unravelling the Late Stages of Stellar Evolution - Supervisor: Simon Jeffery

Stars like our Sun convert hydrogen to helium, grow to become red giants, exchange mass with companions and ultimately run out of fuel and collapse to become a white dwarf, neutron star or black hole. The stellar evolution story is not simple; there are many pathways a star can take and only a few produce “helium stars”. For example, a massive star can blow its hydrogen away,  or a red giant can be stripped of its outer hydrogen by a companion.  A contracting white dwarf can re-ignite and expel its outer layers, or a double white dwarf binary can merge to create a new helium-burning star, and so on.  All these processes are rare and the products are short-lived, so there are relatively few “hydrogen-deficient stars” in the Galaxy, but they come in many different forms, from cool supergiants to hot subdwarfs and from single stars to interacting binaries.

In Armagh we are using the 11m Southern African Large Telescope (SALT) to make the largest multi-epoch survey of hydrogen-deficient stars in the Galaxy, including over 200 helium-rich hot subdwarfs and extreme helium stars. Thes observations will be combined with data from other large-scale surveys including Gaia, TESS, and LAMOST. Objectives will include a full description of stellar properties, distribution and kinematics. The goal is to explore connecttions between subgroups of helium stars and hence to identify evolutionary pathways.

The PhD project will make use of a new generation of models for spectroscopic analysis, as well as new observations from SALT, Gaia, TESS and other surveys. The student will explore tools for automating data analysis, and for visualising the results. Facilities at Armagh will include a new high-performance computer centre (for computing model atmospheres,  data analysis and stellar evolution and pulsation calculations), and a new data visualisation center (for exploring distribution and kinematics).

The student may work on ensemble studies of the entire sample, and hence develop skills in data science for astronomy, or on focused studies of some of the extraordinary individual stars we are discovering, developing skills in stellar atmospheres and/or pulsations. In either case, enthusiasm for both programming and astrophysics will be desirable.

For further information contact simon.jeffery@armagh.ac.uk.

Supermassive Black Holes with Molecular Gas - Supervisor: Marc Sarzi

Supermassive black holes (SMBH) are now known to nearly ubiquitous at the centre of galaxies. The finding of relations between their mass and various galaxy properties imply a tight connection between the growth of SMBHs and that of galaxies. However, the number of reliable SMBH mass measurements is still relatively small, and the number of independent measuring methods is even smaller. In this project, a student would join the WISDOM team (mm-Wave Interferometric Survey of Dark Object Masses) of researchers that has

recently shown how the dense molecular gas of galaxies traces very close the circular velocities dictated by the gravitational potential around galactic nuclei (e.g. the Nature paper of Davis et al. 2013) thus allowing to infer much more accurate and easier measurements for the central SMBH mass.

As part of the WISDOM team (mm-Wave Interferometric Survey of Dark Object Masses), the student will pursue a programme of SMBH mass measurements in a large sample of local galaxies spanning a range of morphological types, masses, and nuclear activities. There are thus much data in hand already, primarily from the ALMA observatory, and the tools necessary to model the velocity fields and estimate uncertainties have already been developed. With these data and machinery, the student will explore how SMBH masses and galaxy properties correlate, in addition to probing the nuclear-scale gas dynamics that allows SMBHs to be fed.
For further information contact marc.sarzi@armagh.ac.uk

The Heaviest Stars and Black Holes in the Universe - Supervisor: Jorick Vink

Some few hundred million years after the Big Bang the universe lit-up by the formation of the First Stars, which are thought to have been very massive owing to their pristine chemistry.

Despite their key role in setting the stage for the subsequent Cosmic chemistry, we know surprisingly little about the evolution & fate of the first few stellar generations.

The goal of this computational PhD project is to predict the amount of the mass the first stellar generations lose through stellar winds, and to determine the final masses of these stars as Black Holes.

The predicted black hole masses will be compared to data from gravitational wave observatories.

For further information contact jorick.vink@armagh.ac.uk

What happens to asteroids in resonances? - Supervisor: Apostolos “Tolis” Christou

The AOP solar system group is carrying out frontline astronomical research in the origin and evolution of the solar system and its small bodies. Recent highlights include: the discovery that the tenuous atmosphere of Mercury is modulated by impacts with debris from periodic comet Encke (Christou, Killen et al, GRL, 2015); using the moons of the giant planets to constrain key events in early solar system evolution (Li and Christou, AJ, 2017; AJ, 2020); and quantifying the evolution of Mars and Earth Trojan asteroids by collisions and radiation forces (Christou et al, Icarus, 2017; Icarus, 2020; Christou & Georgakarakos, MNRAS, 2021). Work by our group
recently showed that Yarkovsky non-gravitational forces cause significant orbit changes or even escape for asteroids in the 1:1 resonance with Mars – the so-called Trojans – while the physical bodies themselves may break apart due to YORP spin-up, creating clusters of resonant asteroids. Outcomes of YORP-induced disruption are observed elsewhere, as orbital clusters of Main Belt asteroids (Pravec et al, 2010) and the active shedding of material (eg (6478) Gault, Hui, M-T et al, MNRAS Lett., 2019). In a wider context, correlations between asteroid orbits and sizes point to size-dependent orbit evolution (Bolin et al, Icarus, 2017; Dermott, Christou et al, Nature Astr., 2018; Dermott et al, MNRAS, 2021).

In this project we want to quantify resonant orbit and/or spin evolution of asteroids and their debris under non-gravitational radiation-driven forces, applying our findings to different settings, make predictions and interpret observations. Breaking up of resonant or co-orbital asteroids near the Earth’s orbit may form compact orbital clusters (de la Fuente Marcos & de la Fuente Marcos, MNRAS Lett., 2019), contribute to debris structures observed at the orbits of the Earth (Dermott et al, Nature, 1994) or, more recently, Venus (Jones et al, Science, 2013; Pokorny & Kuchner, ApJ, 2019). Outside the solar system, any debris in resonance with close-in exoplanets would evolve significantly and rapidly, giving rise to features that may betray the presence of the planetary body. The successful applicant will collaborate with Dr Christou in attacking this multi-faceted problem. The scope and direction of the resulting PhD project will depend primarily on the student’s individual inclinations. Work methods will include, but are not necessarily limited to, intensive N-body numerical simulations. Some familiarity in the areas of dynamics, statistical methods or numerical analysis will be seen as an advantage.

For further information contact Apostolos.Christou@armagh.ac.uk

Finding Meteor Showers on Other Planets - Supervisor: Apostolos “Tolis” Christou

At certain times of the year, the Earth passes through streams of dust left behind by comets, leading to a natural fireworks display: a meteor shower. One of the best-known is the August Perseids; at the peak of the shower, one can see about 100 meteors per hour on a dark clear night. In one of the first successful linkages between a meteor shower and its parent comet, 19th century Italian astronomer Giovanni Schiaparelli proposed in 1867 that the Perseid meteors originate from a comet seen just five years previously and now known as 109P/Swift-Tuttle. The Earth is not the only planet that sweeps up cometary dust in its path. The solar system is, in fact, criss-crossed with streams of debris left behind by comets and asteroids and it is inevitable that some of those intersect the paths of other planets (Christou, MNRAS, 2010; Christou et al, In: “Meteoroids: Sources of Meteors on Earth and Beyond”, CUP, 2019). A case in point is long-period comet C/2013 A1 (Siding Spring) which grazed the planet Mars in 2014 and loaded its upper atmosphere with tons of cometary material. The aftermath was recorded by instruments onboard Mars-orbiting probes like NASA’s MAVEN and ESA’s Mars Express.

Meteor research in the AOP solar system group dates back to the work of E.J. Opik in the 1950s (see eg McFarland & Asher, Proc. Intl. Meteor Conf. 2010). Recent work by our group has aimed to explore how the atmospheres and surfaces of planets can serve as natural area detectors for meteoroids, to probe the nature of near-Earth small bodies through their meteoroid streams, and to test our understanding of meteor showers at the Earth by comparing them with their off-Earth counterparts.

A candidate PhD project in this research area will focus on the stream of comet 2P/Encke incident on the planet Mercury. P/Encke has been linked to several strong daytime and nighttime meteor showers at Earth, the so-called Taurid complex (see Egal et al, MNRAS, 2021, for a review). The NASA MESSENGER spacecraft that orbited Mercury between 2011 and 2015 showed seasonal modulation of Ca in the exosphere. The leading candidate mechanism to explain this seasonality in Ca production is meteoroid impact vaporisation (Killen and Hahn, Icarus, 2015), however models of the sporadic meteoroid environment at Mercury have failed to reproduce the full profile of Ca production rate over time. In 2015 we showed that the Ca production is most likely modulated by impacts with Encke debris and placed constraints on the age and size of the stream meteoroids (Christou, Killen et al, Geophysical Research Letters, 2015; see figure from this NASA press release). This model has so far stood the test of time (Pokorny et al, ApJ, 2018) but important questions remain. The ESA-JAXA Bepicolombo mission is currently on its way to Mercury and its arrival in 2025 will provide further opportunities to test the link between Mercury’s exosphere and the Encke meteor stream (Plainaki et al, JGR (Planets), 2017). It is now necessary to construct higher-fidelity models of this stream, to apply to available MESSENGER data on other exospheric species (eg Na) but also to the new datasets expected from BepiColombo. Project work will include, but may not be limited to, intensive numerical simulations, which has been the state-of-the-art in stream modelling since their successful application to the Leonid meteor storms some 20 yr ago by research staff at Armagh. Familiarity with techniques of dynamical astronomy will be seen as an advantage.

For further information contact apostolos.christou@armagh.ac.uk 

Resolving star formation in the Galactic Plane - Supervisor: David Eden

Our Galaxy, the Milky Way, gives us a unique perspective on studying star formation. Not only can we study the impact of the larger-scale structure of the Galaxy on the star-formation process, but we can also study individual molecular clouds allowing us to investigate the physics on all scales. Doing this opens up some questions: is there an underlying mechanism regulating the star-formation process, and on what scale does this occur; which stage of star formation sets the star-formation efficiency for an entire system; how universal is the process of star formation? To answer these questions, a collection of Galactic Plane surveys tracing multiple different stages of star formation can be combined.

A number of potential science projects are available but are expected to make use of data from the Hi-GAL survey, a Herschel Space ObserKey Project, and surveys from the James Clerk Maxwell Telescope (JCMT) in Hawaii.

These projects will enable the student to learn observational techniques in radio and sub-millimetre astronomy, but projects of a more technical nature are also available. It is expected that there would be opportunities for travelling to Hawaii to complete observations at the JCMT.

For further information contact  davidedenastronomy@gmail.com

Astrophysical Data Visualisation - Supervisor: Michael Burton & Marc Sarzi

This project aims to apply data visualisation techniques to the investigation of complex, multi-dimensional astrophysical data sets.  It brings together astronomy, statistical analysis and data analytics in one project, with the opportunity to use the immersive environment of the Armagh Planetarium to render visualisations in and experiment with audience engagement.  The project lies at the interface of astrophysics and visual analytics.

Several multi-dimensional data sets are available, in particular to study the structure of both the Milky Way galaxy in detail and of external galaxies for a large number objects. For the Milky Way, we aim to investigate the 3D structure of the Milky Way Galaxy using a new data base on the distribution of the molecular gas in the galactic plane that we have obtained using the Mopra radio telescope in Australia.  Combined with data sets on the distribution of dust, interstellar extinction and stars in the Galaxy this can be used to constrain the distances to the spiral arms where the star forming molecular clouds lie. For external galaxies, we aim to use archival MUSE integral-field spectroscopic data obtained with the European Southern Observatory Very Large Telescope for the distribution and motions of the ionised-gas in order to better understand the processes leading to the formation of stars and therefore the growth of galaxies. Ancillary data may also be used for these objects.

For further information contact  Michael.burton@armagh.ac.uk  

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