Cosmic giants shed new light on dark matter

Astronomers at the University of Birmingham, Academica Sinica in Taiwan, and the Kavli Institute of Physics and Mathematics of the Universe in Japan, have found new evidence that the mysterious dark matter that pervades our universe behaves as predicted by the 'cold dark matter' theory known as 'CDM'. At a press conference today (13 June 13) in Taipei the team of astronomers report their measurements of the density of dark matter in the most massive objects in the universe, namely galaxy clusters. They found that the density of dark matter decreases gently from the centre of these cosmic giants out to their diffuse outskirts. The fall in dark matter density from the centre to the outskirts agrees very closely with the CDM theory. Almost eighty years after the first evidence for dark matter emerged from astronomy research, few scientists seriously doubt that it exists. However astronomers cannot see dark matter directly in the night sky, and particle physicists have not yet identified the dark matter particle in their experiments. "What is dark matter?" is therefore a big unanswered question facing astronomers and particle physicists, especially because there is strong evidence that 85% of the mass in the universe is invisible dark matter.