Evidence suggests that the mass of most galaxies is dominated by dark matter.
As it is dark, it is impossible to detect by conventional astronomical means, and so its nature and distribution remains unknown. Dr. Evans is a member of an international team from Oxford, Cambridge, London and Paris universities who are participating in an ambitious new survey of the giant Andromeda galaxy. Since 1999, this galaxy has been monitored four times a night using the Isaac Newton Telescope in La Palma. Microlensing occurs when light travelling towards Earth is deflected by the presence of an intervening mass. Very recently, the survey team has announced the discovery of a short duration microlensing event towards the Andromeda galaxy.