Standard Model may account for Dark Matter and it may be massive

A massive cluster of yellowish galaxies, seemingly caught in a red and blue spider web of eerily distorted background galaxies, makes for a spellbinding picture from the new Advanced Camera for Surveys (ACS) aboard NASA's Hubble Space Telescope. 

To make this unprecedented image of the cosmos, Hubble peered straight through the center of one of the most massive galaxy clusters known, called Abell 1689. 

The gravity of the cluster's trillion stars, plus dark matter, acts as a 2-million-light-year-wide lens in space. 

This gravitational lens bends and magnifies the light of the galaxies located far behind it. Some of the faintest objects in the picture are probably over 13 billion light-years away (redshift value 6). 

Strong gravitational lensing as observed by the Hubble Space Telescope in Abell 1689 indicates the presence of dark matter. 

Credit: NASA, N. Benitez (JHU), T. Broadhurst (Racah Institute of Physics/The Hebrew University), H. Ford (JHU), M. Clampin (STScI),G. Hartig (STScI), G. Illingworth (UCO/Lick Observatory), the ACS Science Team and ESA

The physics community has spent three decades searching for and finding no evidence that dark matter is made of tiny exotic particles.

Case Western Reserve University theoretical physicists suggest researchers consider looking for candidates more in the ordinary realm and, well, more massive.

Dark matter is unseen matter, that, combined with normal matter, could create the gravity that, among other things, prevents spinning galaxies from flying apart.

Physicists calculate that dark matter comprises 27 percent of the universe; normal matter 5 percent.

Instead of WIMPS, weakly interacting massive particles, or axions, which are weakly interacting low-mass particles, dark matter may be made of macroscopic objects, anywhere from a few ounces to the size of a good asteroid, and probably as dense as a neutron star, or the nucleus of an atom, the researchers suggest.

Physics professor Glenn Starkman and David Jacobs, who received his PhD in Physics from CWRU in May and is now a fellow at the University of Cape Town, say published observations provide guidance, limiting where to look.

They lay out the possibilities in a paper "Macro Dark Matter"

The Macros, as Starkman and Jacobs call them, would not only dwarf WIMPS and axions, but differ in an important way.

They could potentially be assembled out of particles in the Standard Model of particle physics instead of requiring new physics to explain their existence.

"We've been looking for WIMPs for a long time and haven't seen them," Starkman said. "We expected to make WIMPS in the Large Hadron Collider (LHC), and we haven't."

WIMPS and axions remain possible candidates for dark matter, but there's reason to search elsewhere, the theorists argue.

"The community had kind of turned away from the idea that dark matter could be made of normal-ish stuff in the late '80s," Starkman said.

"We ask, was that completely correct and how do we know dark matter isn't more ordinary stuff— stuff that could be made from quarks and electrons?"

After eliminating most ordinary matter, including failed Jupiters, white dwarfs, neutron stars, stellar black holes, the black holes in centers of galaxies and neutrinos with a lot of mass, as possible candidates, physicists turned their focus on the exotics.

ESA XMM-Newton: Inexplicable signal provides clue about dark matter

A sketch (not to scale) showing axions (blue) streaming out from the Sun, converting in the Earth's magnetic field (red) into X-rays (orange), which are then detected by the XMM-Newton observatory. 

Credit: University of Leicester

Cutting-edge paper by Professor George Fraser, who tragically died in March this year,and colleagues at the University of Leicester provides first potential indication of direct detection of Dark Matter, something that has been a mystery in physics for over 30 years.

Space scientists at the University of Leicester have detected a curious signal in the X-ray sky – one that provides a tantalising insight into the nature of mysterious Dark Matter.

The Leicester team has found what appears to be a signature of 'axions', predicted 'Dark Matter' particle candidates, something that has been a puzzle to science for years.

In a study being published on Monday 20 October in the Monthly Notices of the Royal Astronomical Society, the University of Leicester scientists describe their finding of a signal which has no conventional explanation.

As first author Professor George Fraser, who sadly died in March of this year, wrote: "The direct detection of dark matter has preoccupied physics for over thirty years."

Dark Matter, a kind of invisible mass of unknown origin, cannot be seen directly with telescopes, but is instead inferred from its gravitational effects on ordinary matter and on light.

Dark Matter is believed to make up 85% of the matter of the Universe.

"The X-ray background, the sky, after the bright X-ray sources are removed - appears to be unchanged whenever you look at it," explained Dr. Andy Read, also from the University of Leicester Department of Physics and Astronomy and now leading the paper.

"However, we have discovered a seasonal signal in this X-ray background, which has no conventional explanation, but is consistent with the discovery of axions."

This result was found through an extensive study of almost the entire archive of data from the European Space Agency's X-ray observatory, XMM-Newton, which will celebrate its 15th year in orbit this December.

Previous searches for axions, notably at CERN, and with other spacecraft in Earth orbit, have so far proved unsuccessful.

As Professor Fraser explains in the paper: "It appears plausible that axions, Dark Matter particle candidates, are indeed produced in the core of the Sun and do indeed convert to X-rays in the magnetic field of the Earth."

It is predicted that the X-ray signal due to axions will be greatest when looking through the sunward side of the magnetic field because this is where the field is strongest.

Dr. Read concludes: "These exciting discoveries, in George's final paper, could be truly ground-breaking, potentially opening a window to new physics, and could have huge implications, not only for our understanding of the true X-ray sky, but also for identifying the Dark Matter that dominates the mass content of the cosmos."

President of the Royal Astronomical Society Professor Martin Barstow, who is Pro-Vice-Chancellor, Head of the College of Science & Engineering and Professor of Astrophysics & Space Science at the University of Leicester said: "This is an amazing result. If confirmed, it will be first direct detection and identification of the elusive dark matter particles and will have a fundamental impact on our theories of the Universe."

More information: "Potential solar axion signatures in X-ray observations with the XMM-Newton observatory," G. W. Fraser, A. M. Read, S. Sembay, J. A. Carter, E. Schyns, Accepted (08/09/14) for publication in Monthly Notices of the Royal Astronomical Society (mnras.oxfordjournals.org/), Paper can be found on arXiv : arxiv.org/abs/1403.2436.