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Astrophysics Research Centre

School of Mathematics and Physics

Christopher (Chris) Watson

About me

I am the head of the extrasolar planet research group, as well as Deputy Head of the School of Mathematics and Physics at Queen's University Belfast. I arrived here in October 2008, following on from a PPARC Postdoctoral fellowship held at Sheffield University (working on binary stars). Now my main interests are in developing methods of reducing the impact of stellar inhomogenities (such as starspots and convection) on the detection and characterisation of extra-solar planets. I am also interested in how hot Jupiters ended up where they are, as well as characterising their atmospheres (QUB was only the 3rd group to recover a z-band secondary eclipse, for example). My activities include involvement in a number of international projects, and I am one of the UK Co-Investigators of the HARPS-N project, as well as Co-Principal Investigator of the Next Generation Transit Survey (NGTS). My research has attracted major national and international press attention, with several global press releases, documentaries in the UK and further afield (such as Australia) with typical viewership measured in the millions. I have also written 'expert' articles for the BBC News, as well as numerous interviews and press articles across the UK/Ireland and globally.

My research

Some recent, important publications by my group that highlight my work in the above areas include:

The changing face of α Centauri B: probing plage and stellar activity in K dwarfs - MNRAS Letter, 2017
Analysis of HARPS spectra of the nearby K2V star, α Centauri B, revealed spectral signatures in photospheric lines attributed to regions of stellar activity on the star. These signals modulate in strength and velocity on the stellar rotation period, but show peculiar morphologies that cannot be explained by spots alone. We propose that a) the signals are more likely to arise from plage and faculae and b) some of the morphological changes are better explained by a varying 'immaculate' photosphere of the star (normally thought of as constant). This has significant implications for confirming Earth-like worlds in the future, since current state-of-the-art stellar jitter removal methods (arising due to stellar signals, and which swamp the smaller signals from Earth-analog planets) rest on assuming the 'inactive' photosphere is constant in time. We propose that this assumption is incorrect. However, the direct detection of such signals in α Centauri B raises the prospect that such changes can be tracked, as well as potentially opening up a route for determining the absolute spot and plage coverage on host stars. This latter prospect would also aid in the atmospheric characterisation of exoplanets.

A Window on Expoplanet Dynamical Histories: Rossiter-McLaughlin Observations of WASP-13b and WASP-32b - MNRAS, 2014
We know that many of the large, gaseous planets currently orbiting extremely close to their parent stars (with orbital periods sometimes less than a day!) could not have formed in such a hostile environment. Instead, they formed much further out, and then some mechanism caused them to migrate inwards to their present position. The Rossiter-McLaughlin (RM) effect can be used to constrain whether the orbit of a transiting planet is aligned (or not) with the spin of the host star. It used to be thought that if the spin axes of the orbit and the parent star were observed to be nicely aligned, then migration occured via some interaction with the surrounding proto-planetary disc that formed them. If the orbits were seen to be misaligned (and we know of planets with retrograde orbits) then the assumption was that some other dynamically turbulent process was responsible for the migration. In this paper we present 2 more RM observations of transiting exoplanets, and determine the true '3D' system geometry of WASP-32b (only the 12th measure of its kind) - finding both to be well aligned. We then present evidence that planets may act to force the star to spin in the same direction as the planet. We speculate (amongst others) that the majority of planets that have migrated to close-in orbits may have done so via some violent mechanism (e.g. planetary collisions) but if the tidal dissipation timescale of the system is short enough then the planet will realign the host star (or, at least, its outer convective envelope). In this scenario, planets that have undergone migration by some violent means can masquerade as well-aligned systems that would previously have been interpreted as having undergone gentle migration through the planet-forming disc. We present more evidence of a preference for systems with short tidal dissipation timescales to be aligned, whereas planets in systems with long tidal dissipation timescales are misaligned - currently supporting this interpretation.

An Earth-sized planet with an Earth-like density - Nature Letter, 2013
NASA's space-based Kepler mission has produced transformational science, yielding a clutch of 1000's of potential planetary candidates using the transit method. These transiting planets are highly valued, the periodic dips in the lightcurve as the planet transits its host star enable the planetary radius to be determined to high precision. If it is possible to then 'weigh' the planet by measuring the Doppler wobble its orbit induces on the host star, then it becomes possible to determine the planet's bulk density, and hence infer its composition. Indeed, given that some astronomical objects can masquerade as transting planets, measuring the mass of a candidate is the best way of determining whether such an object truly is a planet. A few planet candidates with a minimum-mass OR size similar to the Earth have been identified. This paper presents, for the first time, the determination of both the size and mass of one of them - Kepler-78b. From this we determine the planet's mean density, which turns out to be very similar to Earth's and is consistent with an Earth-like composition of rock and iron. There the similarity with Earth ends - with an orbital period of just 8.5 hours, the planet is so hot that its surface will be molten!

Other research activities

In addition to these programmes, I am also a co-PI of the Next Generation Transit Survey (NGTS), and one of 3 UK-CoI's of the HARPS-N project, aimed at providing masses of planet candidates identified by NASA's Kepler space misison.

I am also the Work Package manager of WP115100 ("Astrophysical Noise Sources") for the ~€650M PLAnetary Transits and Oscillations (PLATO) mission, adopted for launch by the European Space Agency. Coupled to this, I am the Team Lead for the International Space Science Institute's (ISSI) International Team programme - "Towards Earth-like alien worlds: Know thy star, know thy planet", selected in June 2018.

I have also had the pleasure of supervising several PhD students through to completion, and they have gone on to a number of different roles, both in and out of academia including: Liberty IT, Fellowships (Toronto, Geneva), Postdoctoral positions (Leicester, Cambridge, Toulouse), and a Mathematics Programme Support Tutor at Manchester Metropolitan University. Publication lists can be seen here:

PhD publications.

PhD publications.

PhD Publications.

PhD Publications.

PhD publications.

You can find more details about my research on this page and here is a link to my publication list from ADS. Please note that, since ADS updated their system, it regularly does not correctly list all my publications, at other times it does….

I also have a list of my grant and facility income.

Other duties (outside QUB)

  • Chairman of the Astronomical Science Group of Ireland (Feb 2013- Feb 2016), and founder of the Irish National Astronomy Meeting (INAM).
  • Member of the Royal Irish Academy Astronomy and Space Sciences Committee (2014-2015).
  • Committee member of UKON (United Kingdom Optical and Near-Infrared Telescope Users' Group - formerly the UK 8-m Users Group).
  • STEM Ambassador.
  • PATT Chairman (01/09/2015 - 31/12/2018). Previously panel member of the STFC PATT ING Time Allocation Group (from 01/09/2011 - 31/08/2013).
  • PPRP panel expert member (2015/16).
  • Member of the UK Exoplanet Research Review panel (2014-15). The review document can be accessed here.
  • Chair of the UK Space Agency Ariel Science Review panel (2018).
  • Member of the UK Space Agency Project Management Board for Ariel (2018 - current).
  • Member of the STFC PATT grant panel (2018-current).
  • Member of the STFC Astronomy Evaluation Panel (2018 - current).
  • Member of the ING Scientific Advisory Committee (2020 - current).

Other duties (within QUB)

  • Deputy Head of School.
  • PHY4005 Module Coordinator.

You can find further information on my teaching activities here.

Public Outreach

I am heavily involved in public outreach, including multiple radio and TV appearances, including filming for a BBC Horizons documentary, as well as global press releases related to my research. Just some examples of press releases and articles include:

Commentary on the K2-290 system from 15th Feb 2021: NewScientist

Expert article on "What makes a planet habitable?": BBC News

Commentary on NASA's 'Earth-2.0' Kepler announcement: BBC News

BBC Horizon press coverage from March 2015: BBC News

Kepler-10c press release from 2nd June 2014: BBC News

Just a few of the Kepler-78 press releases, some I'm on…: BBC News, Sky News, The Telegraph, The Mirror, The Daily Mail, The Pakistan Defence (!!), Norway, Info OGGI (Italy), Vietnam news, Bosnia & Herzegovina

users/cawatson/start.txt · Last modified: 2021/02/17 14:14 by cawatson

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