Dark matter is 25 times more abundant than mere visible matter, so visible matter should cluster wherever dark matter clusters. The ghost universe of dark matter is a template for the visible universe, she said. Several other groups over the past two years have also showed similar clumping. Ma, Bertschinger and UC Berkeley graduate student Michael Boylan-Kolchin performed some of these simulations themselves. The dark world has a dynamic life of its own.' People were intrigued to find that high-resolution simulations show they are not smooth, but instead have intricate substructures. 'But each of these clumps, the halo around galaxy clusters, was thought to be smooth.

'The cosmic microwave background shows the early effects of dark matter clumping, and these clumps grow under gravitational attraction,' she said. The dark matter has a dynamic life independent of luminous matter, she said. Instead, dark matter forms smaller clumps that look superficially like the galaxies and globular clusters we see in our luminous universe. The cosmic account now pegs dark energy at about 69 percent of the universe, exotic dark matter at 27 percent, mundane dark matter - dim, unseen stars - at 3 percent, and what we actually see at a mere 1 percent.īased on computer models of how dark matter would move under the force of gravity, Ma said that dark matter is not a uniform mist enveloping clusters of galaxies. The picture only got worse four years ago when 'dark energy' was found to be even more prevalent than dark matter. 'They're too heavy to produce now in accelerators, so half of the world we don't know about.' 'We're only seeing half of all particles,' Ma said. Because these exotic particles interact with ordinary matter through gravity only, not via electromagnetic waves, they emit no light. Early proposals that the invisible matter is comprised of burnt-out stars or heavy neutrinos have not panned out, and the current favorite candidates are exotic particles variously called neutrilinos, axions or other hypothetical supersymmetric particles. This unseen matter seems to be in a spherical halo that extends probably 10 times farther than the visible stellar halo around galaxies. Stars within galaxies and galaxies within clusters move in a way that indicates there is more matter there than we can see. Their findings should provide astrophysicists with a new way to calculate the evolution of this ghost universe of dark matter and reconcile it with the observable universe, Ma said.ĭark matter has been a nagging problem for astronomy for more than 30 years.

In a paper submitted this week to Physical Review D, Chung-Pei Ma, an associate professor of astronomy at UC Berkeley, and Edmund Bertschinger of the Massachusetts Institute of Technology (MIT), prove that the motion of dark matter clumps can be modeled in a way similar to the Brownian motion of air-borne dust or pollen.

Dark matter a ghost story