Nav: Home

Cosmic x-rays may provide clues to the nature of dark matter

February 08, 2018

Dark matter is increasingly puzzling. 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 dark matter particles may be very different from what is normally assumed. 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 particles instead.

According to common theory, dark matter must exist because otherwise stars would not continue to rotate around the center of their galaxies as they in fact do. 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. "We, too, are currently actively on the search for possible alternatives," said Professor Joachim Kopp of Mainz University.

The physicist, 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.

X-ray radiation produced by the annihilation of dark matter

The PRISMA researchers propose a scenario in which two dark matter particles collide, resulting in their mutual annihilation. This is analogous to what happens, for instance, when an electron meets with its antiparticle, a positron. "It has long been assumed that it would not be possible to observe such annihilation of dark matter if it were made of particles that light," explained Kopp. "We have subjected our new model to scrutiny and have compared it with experimental data, and it all fits together much better than in the case of older models."

According to Kopp's model, dark matter particles would be fermions with a mass of only a few kiloelectron volts, frequently called sterile neutrinos. Such lightweight dark matter is usually considered problematic because it makes it difficult to explain how galaxies could have been formed. "So far, we have been able to deal with these concerns," explained Kopp. "Our model provides an elegant way out." The supposition that the annihilation of dark matter is a two-step process is of crucial importance in this context: during the initial stage of the process, an intermediate state is formed, which later disintegrates into the observed x-ray photons. "The results of our calculations show that the resulting x-ray signature correlates closely with the observations and thus offers a novel explanation for these," added Kopp.

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. Theoretical and experimental physicists at JGU are currently working on the proposed ESA mission e-ASTROGRAM, which aims at analyzing astrophysical x-ray radiation with previously unachieved accuracy.

Johannes Gutenberg Universitaet Mainz

Related Dark Matter Articles:

New technique looks for dark matter traces in dark places
A new study by scientists at Lawrence Berkeley National Laboratory, UC Berkeley, and the University of Michigan -- published today in the journal Science - concludes that a possible dark matter-related explanation for a mysterious light signature in space is largely ruled out.
Researchers look for dark matter close to home
Eighty-five percent of the universe is composed of dark matter, but we don't know what, exactly, it is.
Galaxy formation simulated without dark matter
For the first time, researchers from the universities of Bonn and Strasbourg have simulated the formation of galaxies in a universe without dark matter.
Taking the temperature of dark matter
Warm, cold, just right? Physicists at UC Davis are using gravitational lensing to take the temperature of dark matter, the mysterious substance that makes up about a quarter of our universe.
New clues on dark matter from the darkest galaxies
Low-surface-brightness (LSB) galaxies offered important confirmations and new information on one of the largest mysteries of the cosmos: dark matter.
DNA repeats -- the genome's dark matter
First direct analysis of pathogenic sequence repeats in the human genome.
A new approach to the hunt for dark matter
A study that takes a novel approach to the search for dark matter has been performed by the BASE Collaboration at CERN working together with a team at the PRISMA+ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU).
Could the mysteries of antimatter and dark matter be linked?
RIKEN researchers and collaborators have performed the first laboratory experiments to determine whether a slightly different way in which matter and antimatter interact with dark matter might be a key to solving both mysteries.
Placing another piece in the dark matter puzzle
A team led by Prof Dmitry Budker has continued their search for dark matter within the framework of the 'Cosmic Axion Spin Precession Experiment' (or 'CASPEr' for short).
Physicists have found a way to 'hear' dark matter
Physicists at Stockholm University and the Max Planck Institute for Physics have turned to plasmas in a proposal that could revolutionise the search for the elusive dark matter.
More Dark Matter News and Dark Matter Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Teaching For Better Humans 2.0
More than test scores or good grades–what do kids need for the future? This hour, TED speakers explore how to help children grow into better humans, both during and after this time of crisis. Guests include educators Richard Culatta and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

One of the most consistent questions we get at the show is from parents who want to know which episodes are kid-friendly and which aren't. So today, we're releasing a separate feed, Radiolab for Kids. To kick it off, we're rerunning an all-time favorite episode: Space. In the 60's, space exploration was an American obsession. This hour, we chart the path from romance to increasing cynicism. We begin with Ann Druyan, widow of Carl Sagan, with a story about the Voyager expedition, true love, and a golden record that travels through space. And astrophysicist Neil de Grasse Tyson explains the Coepernican Principle, and just how insignificant we are. Support Radiolab today at