Research Fellows Directory
Dr Richard Massey
University of Durham
The night sky contains a huge amount of stars, galaxies and dust. Everything we see there is made of the same elements from the periodic table as our bodies, the air we breathe, and the sheet of paper (or computer screen) that you're looking at. Particle physicists understand the periodic table fairly well, through a "standard model" of electrons, protons, quarks, and so on.
However, evidence is mounting that this is only a few percent of the total amount of stuff in the Universe. Six times as much mass is in the form of invisible "dark matter", a cosmic glue whose gravity holds galaxies and clusters of galaxies together. Dark matter even slowed the expansion of the entire Universe out of the Big Bang and kept ordinary matter sufficiently concentrated to form stars and to evolve life. A third ingredient, known as “dark energy”, acts against the gravitational pull of dark matter. It has become gradually stronger throughout the lifetime of the Universe, and is currently re-accelerating its overall expansion. Embarassingly, almost nothing is known about the dark Universe.
Dark matter is invisible, which makes it hard to study - but not impossible! The best way is via "gravitational lensing". Light rays from a distant galaxy do not travel in perfectly across the Universe to us, but are bend ant deflected when they pass near anything heavy. So even though we can see neither dark matter nor dark energy, we observe the images of background galaxies distorted into characteristic patterns that belie their presence. I have mapped dark matter on the largest scales using the Hubble Space Telescope, and am currently zooming in on regions of particular interest. These include mergers between galaxy clusters, which act as giant particle colliders. Just like particle physicists smash atoms to understand their constituents, by watching where the dark matter debris ends up, I am trying to categorise its behaviour and understand its nature.
Interests and expertise (Subject groups)