Dark matter may be more massive than previously thought

A new study has revealed that no evidence has been found that dark matter is made of tiny exotic particles, and it might be more massive.

ANI| Last Updated: Nov 05, 2014, 13:43 PM IST

Washington: A new study has revealed that no evidence has been found that dark matter is made of tiny exotic particles, and it might be more massive.

Researchers from Case Western Reserve University found that dark matter comprises 27 percent of the universe, while normal matter comprises just 5 percent.

Scientists suggested that 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.

Physics professor Glenn Starkman and David Jacobs said that published observations provide guidance, limiting where to look and that the Macros 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.

The Macros would have to be assembled from ordinary and strange quarks or baryons before the strange quarks or baryons decay, and at a temperature above 3.5 trillion degrees Celsius, comparable to the temperature in the center of a massive supernova, Starkman and Jacobs calculated. The quarks would have to be assembled with 90 percent efficiency, leaving just 10 percent to form the protons and neutrons found in the universe today.

The scientists found that a minimum of 55 grams and if dark matter were smaller, it would have been seen in detectors in Skylab or in tracks found in sheets of mica, while a maximum of 1024 (a million billion billion) grams, above this, the Macros would be so massive they would bend starlight, which has not been seen.

It was also revealed that the range of 1017 to 1020 grams per centimeter squared should also be eliminated from the search, the theorists say. Dark matter in that range would be massive for gravitational lensing to affect individual photons from gamma ray bursts in ways that have not been seen and if dark matter is within this allowed range, there are reasons it hasn't been seen.

At the mass of 1018 grams, dark matter Macros would hit the Earth about once every billion years, while at lower masses, they would strike the Earth more frequently but might not leave a recognizable record or observable mark and in the range of 109 to 1018, dark matter would collide with the Earth once annually, providing nothing to the underground dark matter detectors in place.