Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Dark matter even darker than once thought

27.03.2015

Hubble explores the dark side of cosmic collisions

Astronomers using observations from the NASA/ESA Hubble Space Telescope and NASA's Chandra X-ray Observatory have studied how dark matter in clusters of galaxies behaves when the clusters collide. The results, published in the journal Science on 27 March 2015, show that dark matter interacts with itself even less than previously thought, and narrows down the options for what this mysterious substance might be.


This collage shows NASA/ESA Hubble Space Telescope images of six different galaxy clusters. The clusters were observed in a study of how dark matter in clusters of galaxies behaves when the clusters collide. 72 large cluster collisions were studied in total.

The clusters shown here are, from left to right and top to bottom: MACS J0416.1-2403, MACS J0152.5-2852, MACS J0717.5+3745, Abell 370, Abell 2744 and ZwCl 1358+62.

Credit

NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland), R. Massey (Durham University, UK), the Hubble SM4 ERO Team, ST-ECF, ESO, D. Coe (STScI), J. Merten (Heidelberg/Bologna), HST Frontier Fields, Harald Ebeling(University of Hawaii at Manoa), Jean-Paul Kneib (LAM)and Johan Richard (Caltech, USA)

Dark matter is a giant question mark looming over our knowledge of the Universe. There is more dark matter in the Universe than visible matter, but it is extremely elusive; it does not reflect, absorb or emit light, making it invisible. Because of this, it is only known to exist via its gravitational effects on the visible Universe (see e.g. heic1215a).

To learn more about this mysterious substance, researchers can study it in a way similar to experiments on visible matter -- by watching what happens when it bumps into things [1]. For this reason, researchers look at vast collections of galaxies, called galaxy clusters, where collisions involving dark matter happen naturally and where it exists in vast enough quantities to see the effects of collisions [2].

Galaxies are made of three main ingredients: stars, clouds of gas and dark matter. During collisions, the clouds of gas spread throughout the galaxies crash into each other and slow down or stop. The stars are much less affected by the drag from the gas [3] and, because of the huge gaps between them, do not have a slowing effect on each other -- though if two stars did collide the frictional forces would be huge.

"We know how gas and stars react to these cosmic crashes and where they emerge from the wreckage. Comparing how dark matter behaves can help us to narrow down what it actually is," explains David Harvey of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, lead author of a new study.

Harvey and his team used data from the NASA/ESA Hubble Space Telescope and NASA's Chandra X-ray Observatory to study 72 large cluster collisions. The collisions happened at different times, and are seen from different angles -- some from the side, and others head-on [4].

The team found that, like the stars, the dark matter continued straight through the violent collisions without slowing down. However, unlike in the case of the stars, this is not because the dark matter is far away from other dark matter during the collisions. The leading theory is that dark matter is spread evenly throughout the galaxy clusters so dark matter particles frequently get very close to each other. The reason the dark matter doesn't slow down is because not only does it not interact with visible particles, it also interacts even less with other dark matter than previously thought.

"A previous study had seen similar behaviour in the Bullet Cluster," says team member Richard Massey of Durham University, UK. "But it's difficult to interpret what you're seeing if you have just one example. Each collision takes hundreds of millions of years, so in a human lifetime we only get to see one freeze-frame from a single camera angle. Now that we have studied so many more collisions, we can start to piece together the full movie and better understand what is going on."

By finding that dark matter interacts with itself even less than previously thought, the team have successfully narrowed down the properties of dark matter. Particle physics theorists have to keep looking, but they now have a smaller set of unknowns to work with when building their models[5].

Dark matter could potentially have rich and complex properties, and there are still several other types of interaction to study. These latest results rule out interactions that create a strong frictional force, causing dark matter to slow down during collisions. Other possible interactions could make dark matter particles bounce off each other like billiard balls, causing dark matter to be thrown out of collisions or for dark matter blobs to change shape. The team will be studying these next.

To further increase the number of collisions that can be studied, the team are also looking to study collisions involving individual galaxies, which are much more common.

"There are still several viable candidates for dark matter, so the game is not over, but we are getting nearer to an answer," concludes Harvey. "These 'Astronomically Large' particle colliders are finally letting us glimpse the dark world all around us but just out of reach."

###

Notes

[1] On Earth scientists use particle accelerators to find out more about the properties of different particles. Physicists can investigate what substances are made of by accelerating particles into a collision, and examining the properties and trajectory of the resulting debris.

[2] Clusters of galaxies are a swarm of galaxies permeated by a sea of hot X-ray emitting ionised hydrogen gas that is all embedded in a massive cloud of dark matter. It is the interactions of these, the most massive structures in the Universe that are observed to test dark matter's properties.

[3] The gas-gas interaction in cluster collisions is very strong, while the gas-star drag is weak. In a similar way to a soap bubble and a bullet in the wind where the bubble would interact a great deal more with the wind than the bullet.

[4] To find out where the dark matter was located in the cluster the researchers studied the light from galaxies behind the cluster whose light had been magnified and distorted by the mass in the cluster. Because they have a good idea of the visible mass in the cluster, the amount the light is distorted tells them how much dark matter there is in a region.

[5] A favoured theory is that dark matter might be constituted of "supersymmetric" particles. Supersymmetry is a theory in which all particles in our Standard Model -- electrons, protons, neutrons, and so on -- have a more massive "supersymmetric" partner. While there has been no experimental confirmation for supersymmetry as yet, the theory would solve a few of the gaps in our current thinking. One of supersymmetry's proposed particles would be stable, electrically neutral, and only interact weakly with the common particles of the Standard Model -- all the properties required to explain dark matter.

Notes for editors

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The research paper, entitled "The non-gravitational interactions of dark matter in colliding galaxy clusters", will be published in the journal Science on 27 March 2015.

The international team of astronomers in this study consists of D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland; University of Edinburgh, UK), R. Massey (Durham University, UK), T. Kitching (University College London, UK), A. Taylor (University of Edinburgh, UK), and E. Tittley (University of Edinburgh, UK).

More information

Image credit: NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland) and R. Massey (Durham University, UK)

Links

Images of Hubble - http://www.spacetelescope.org/images/archive/category/spacecraft/

Link to science paper - http://www.spacetelescope.org/static/archives/releases/science_papers/heic1506a.pdf

Contacts

David Harvey
École Polytechnique Fédérale de Lausanne
Lausanne, Switzerland
Tel: +41 22 3792475
Cell: +41 7946 38283
Email: david.harvey@epfl.ch

Richard Massey
Durham University
Durham, UK
Tel: +44 7740 648080
Email: r.j.massey@durham.ac.uk

Georgia Bladon
ESA/Hubble, Public Information Officer
Garching bei München, Germany
Tel: +44 7816 291261
Email: gbladon@partner.eso.org

Media Contact

Georgia Bladon
gbladon@partner.eso.org
44-781-629-1261

 @hubble_space

http://www.spacetelescope.org 

Georgia Bladon | EurekAlert!

Further reports about: ESA Galaxies Hubble NASA Polytechnique Universe collisions dark dark matter interactions

More articles from Physics and Astronomy:

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

nachricht What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>