February 08, 2018
from ScienceDaily Website
a new theory of dark matter
based on the detection of
unusual x-ray radiation
Around the world, physicists have been trying for decades to determine the nature of these matter particles, which do not emit light and are therefore invisible to the human eye.
Their existence was postulated in the 1930s to explain certain astronomical observations.
As visible matter, like the one that makes up the stars and the Earth, constitutes just 5 percent of the universe, it has been proposed that dark matter must represent 23 percent of what is out there.
But to date and despite intensive research, it has proved impossible to actually identify the particles involved.
Researchers at Johannes Gutenberg University Mainz (JGU) have now presented a novel theory of dark matter, which implies that,
In particular, their
theory involves dark matter particles which are extremely light -
almost one hundred times lighter than electrons, in stark contrast
to many conventional models that involve very heavy dark matter
Among the particularly favored candidates for dark matter are so-called weakly interacting massive particles, or WIMPs. Researchers are searching for these in the Italian Gran Sasso underground laboratory, for example.
But recent scientific publications in the field of astroparticle physics are increasingly taking the view that WIMPs are unlikely to be viable prospects when it comes to dark matter.
The physicist Joachim Kopp, together with his colleagues Vedran Brdar, Jia Liu, and Xiao-Ping Want, took a closer look at the results of observations undertaken by several independent groups in 2014.
The groups reported the presence of a previously undetected spectral line, with an energy of 3.5 kiloelectron volts (keV), in x-ray light from distant galaxies and galaxy clusters.
This unusual x-ray radiation might offer a clue to the nature of dark matter. It has been previously pointed out that dark matter particles might decay, thereby emitting x-rays.
However, Joachim Kopp's team at the Mainz-based Cluster of Excellence on Precision Physics, Fundamental Interactions and Structure of Matter (PRISMA) is taking another approach.
This is analogous to what happens, for instance, when an electron meets with its antiparticle, a positron.
Such lightweight dark matter is usually considered problematic because it makes it difficult to explain how galaxies could have been formed.
The supposition that the annihilation of dark matter is a two-step process is of crucial importance in this context:
At the same time, the new model itself is so general that it will offer an interesting starting point for the search for dark matter even if it turns out that the spectral line discovered in 2014 has a different origin.
experimental physicists at JGU are currently working on the proposed
ESA mission e-ASTROGRAM, which aims
at analyzing astrophysical x-ray radiation with previously