Dark matter appears to make up more of our Universe than ordinary matter, and the first hard evidence of the presence of the material may have been detected by physicists.
Astronomers noted decades ago that the amount of ordinary matter in the Universe is not great enough to account for the motions of stars in galaxies, or observed gravitational forces.
The theory of dark matter was developed in an effort to understand how galaxies rotate in the manner observed by astronomers. The material is theorized to not emit light or other wavelengths of electromagnetic radiation and to interact with other material in the Universe solely through gravitational effects.
Astrophysicists from Ecole Polytechnique Federale de Lausanne (EPFL) Laboratory of Particle Physics and Cosmology (LPPC), working with researchers from Leiden University, analyzed X-rays from the Andromeda galaxy and the Perseus galaxy cluster.
X-ray observations from the orbiting XMM-Newton telescope, managed by the European Space Agency were examined by the researchers. They removed all signals from known sources and particles. A signal remained that could not be explained by astronomers, through the actions of ordinary matter.
"[T]he signal's distribution within the galaxy corresponds exactly to what we were expecting with dark matter, that is, concentrated and intense in the center of objects and weaker and diffuse on the edges," Oleg Ruchayskiy of EPFL said.
When researchers looked at measurements taken of the Milky Way, our own galaxy was also found to exhibit similar evidence of the presence of dark matter.
This signal could be produced through a rare process - an emission of a photon through the destruction of a theoretical "sterile neutrino." These hypothetical particles do not interact through any fundamental interaction other than gravity. They are so elusive, they are popularly referred to as a "ghost of a ghost."
"Neutrino masses suggests the existence of right-handed degrees of freedom, the sterile neutrinos," Kalliopi Petraki of the University of Melbourne wrote for Fermilab in Sterile Neutrinos as Dark Matter.
If physicists are correct, the Universe contains four times as much dark matter as normal everyday matter.
"Confirmation of this discovery may lead to construction of new telescopes specially designed for studying the signals from dark matter particles. We will know where to look in order to trace dark structures in space and will be able to reconstruct how the Universe has formed," Alexey Boyarsky of Leiden University stated in a press release.
Possible detection of the presence of dark matter will be profiled in an upcoming issue of the journal Physical Review Letters.