Geraint F. Lewis

Welsh astronomer born in Neath

Geraint F. Lewis (born 14 March 1969) is a Welsh astrophysicist and winner of the 2016 Walter Boas Medal.

Prof Geraint F. Lewis at the Sydney Institute for Astronomy at the University of Sydney.


  • If dark matter is in the form of stellar mass compact objects, then the extremes of such variability are accessible to a monitoring campaign with the Hubble Space Telescope. With the advent of the Next Generation Space Telescope, cluster dark matter in the form of compact objects will induce a ubiquitous ‘shimmering’ of the giant arcs.
    • (2001). "Gravitational Microlensing of Giant Luminous Arcs: a Test for Compact Dark Matter in Clusters of Galaxies". Publications of the Astronomical Society of Australia 18 (2): 182-185. DOI:10.1071/AS01025.
  • If planetary systems are ubiquitous then a fraction of stars should possess a transiting planet when being microlensed. ... For the giant planets recently identified, the deviations in the light curve can be substantial, although the specifics of the perturbations are dependent upon the radius of the planet relative to that of the star, the location of the planet over the stellar surface and the orientation of the sweeping caustic. Given that the instantaneous probability of transiting hot-Jupiter like planets is small, less than a percent, and only a proportion of microlensing events exhibit caustic crossing events, the probability of detecting a transiting planet during a microlensing event is small, ~10-6. However, a number of factors influencing this probability, such as the number of solar type star that possess planets, are uncertain, and the prospect of detecting transiting planets in future large catalogues of microlensing light curves may be viable.

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