Zooming In Tight on Dark Matter – Equivalent of Being Able to See a Flea on the Surface of the Moon

Projected Dark Matter Density Map

Projected dark matter density map, created using a simulation measuring 2.4 billion light years on each side. The inset square (bottom left) is the deepest zoom in the simulation: it is only 783 light-years across, equivalent to 500 times the size of the solar system. In the inset square, the smallest clearly visible dark matter haloes have a mass comparable to that of the Earth (0.000003 the mass of the Sun). Credit: Dr. Sownak Bose, Center for Astrophysics, Harvard University

Cosmologists have zoomed in on the smallest clumps of dark matter in a virtual universe — which could help us to find the real thing in space.

An international team of researchers, including Durham University, UK, used supercomputers in Europe and China to focus on a typical region of a computer-generated universe.

The zoom they were able to achieve is the equivalent of being able to see a flea on the surface of the Moon.

This allowed them to make detailed pictures and analyses of hundreds of virtual dark matter clumps (or haloes) from the very largest to the tiniest.

Dark matter particles can collide with dark matter anti-particles near the center of haloes where, according to some theories, they are converted into a burst of energetic gamma-ray radiation.

Their findings, published in the prestigious journal Nature, could mean that these very small haloes could be identified in future observations by the radiation they are thought to give out.

Dark Matter Haloes

An artist’s impression of dark matter haloes with various masses in the Universe. Credit: YU Jingchuan, Beijing Planetarium

Co-author Professor Carlos Frenk, Ogden Professor of Fundamental Physics at the Institute for Computational Cosmology, at Durham University, UK, said: “By zooming in on these relatively tiny dark matter haloes we can calculate the amount of radiation expected to come from different sized haloes.

“Most of this radiation would be emitted by dark matter haloes too small to contain stars and future gamma-ray observatories might be able to detect these emissions, making these small objects individually or collectively ‘visible’.

“This would confirm the hypothesized nature of the dark matter, which may not be entirely dark after all.”

Most of the matter in the universe is dark (apart from the gamma radiation they emit in exceptional circumstances) and completely different in nature from the matter that makes up stars, planets, and people.

The universe is made of approximately 27 percent dark matter with the rest largely consisting of the equally mysterious dark energy. Normal matter, such as planets and stars, makes up a relatively small five percent of the universe.

Galaxies formed and grew when gas cooled and condensed at the center of enormous clumps of this dark matter — so-called dark matter haloes.

Astronomers can infer the structure of large dark matter haloes from the properties of the galaxies and gas within them.

The biggest haloes contain huge collections of hundreds of bright galaxies, called galaxy clusters, weighing 1,000 trillion times more than our Sun.

Projected Dark Matter Density

Projected dark matter density map, created using a simulation measuring 2.4 billion light years on each side. The intermediate square (top right) is just under a million light-years across. The smallest square (bottom left) is the deepest zoom: it is only 783 light-years across, equivalent to 500 times the size of the solar system. In the intermediate square(top right) the largest dark matter haloes have a mass similar to that of a rich galaxy cluster (a million trillion times the mass of the Sun). In the smallest square (bottom right) the smallest clearly visible haloes have a mass comparable to that of the Earth (0.000003 the mass of the Sun). Credit: Dr. Sownak Bose, Center for Astrophysics, Harvard University

However, scientists have no direct information about smaller dark matter haloes that are too tiny to contain a galaxy. These can only be studied by simulating the evolution of the Universe in a large supercomputer.

The smallest are thought to have the same mass as the Earth according to current popular scientific theories about dark matter that underlie the new research.

The simulations were carried out using the Cosmology Machine supercomputer, part of the DiRAC High-Performance Computing facility in Durham, funded by the Science and Technology Facilities Council (STFC), and computers at the Chinese Academy of Sciences.

By zooming in on the virtual universe in such microscopic detail, the researchers were able to study the structure of dark matter haloes ranging in mass from that of the Earth to a big galaxy cluster.

Surprisingly, they found that haloes of all sizes have a very similar internal structure and are extremely dense at the center, becoming increasingly spread out, with smaller clumps orbiting in their outer regions.

The researchers said that without a measure scale it was almost impossible to tell an image of a dark matter halo of a massive galaxy from one of a halo with a mass a fraction of the Sun’s.

Co-author Professor Simon White, of the Max Planck Institute of Astrophysics, Germany, said: “We expect that small dark matter haloes would be extremely numerous, containing a substantial fraction of all the dark matter in the universe, but they would remain mostly dark throughout cosmic history because stars and galaxies grow only in haloes more than a million times as massive as the Sun.

“Our research sheds light on these small haloes as we seek to learn more about what dark matter is and the role it plays in the evolution of the universe.”

Reference: “Universal structure of dark matter haloes over a mass range of 20 orders of magnitude” by J. Wang, S. Bose, C. S. Frenk, L. Gao, A. Jenkins, V. Springel and S. D. M. White, 2 September 2020, Nature.
DOI: 10.1038/s41586-020-2642-9

The research team, led by the National Astronomical Observatories of the Chinese Academy of Sciences, and including Durham University, UK, the Max Planck Institute for Astrophysics, Germany, and the Center for Astrophysics in Harvard, USA, took five years to develop, test and carry out their cosmic zoom.

The research was funded by the STFC, the European Research Council, the Chinese Academy of Sciences, the Max Planck Society and Harvard University.

11 Comments on "Zooming In Tight on Dark Matter – Equivalent of Being Able to See a Flea on the Surface of the Moon"

  1. Wow, great they’ve finally found dark matter! In a virtual universe at that. At least they’ve finally found it somewhere, lol. More funds that could have gone to other more legitimate areas of inquiry in cosmology gobbled up by the dark matter snipe hunt.

    • Torbjörn Larsson | September 3, 2020 at 12:19 pm | Reply

      Dark matter is not only legitimate, it has been observed by all sorts of independent measurements starting from cosmic background spectra – you can’t explain it without dark matter – over cosmic filaments down to dwarf galaxies. In all cases, only the accepted dark matter cosmology does the job.

      Doing your own “snipe hunt” – based on rejecting what the presented work tells you – makes your comment irony.

      • Untrue. No one even knows what dark matter even is, and it’s called “dark” because it’s undetectable. Effects have been observed, that by default are attributed to something that’s been labeled “dark matter.” And to make the absolute claim that “only” dark matter does the job is ridiculous, not to mention totally anti-scientific.

  2. It’s a wild goose chase that’s going to continue for around another 6 years imo. That’s when the PSYCHE spacecraft will confirm a major gravity anomaly from a metallic asteroid core remnant. Only then will scientists look beneath their feet for what they have been searching for all along.

    • Torbjörn Larsson | September 3, 2020 at 12:21 pm | Reply

      Scientists look for all possibilities naturally, else someone else will make the finds.

      Dark matter has been observed many times by many means [c.f. the references in the linked work]. How is that “a goose chase”?

  3. … There are more and more questions than answers, though.
    For an example, when one has a two masses and they attract each other at the rest, is the force just the same to the force when those two masses are approaching the speed of light?
    Strange are that dark matter thing, for sure…

  4. Wow, so many laypeople in here who know dark matter better than the entire scientific community of highly trained and experienced researchers. What are the odds?

  5. Torbjörn Larsson | September 3, 2020 at 12:15 pm | Reply

    That they see cusped clumps like the early dark matter halo models is no surprise. For galactic halos the dark matter models were complemented with normal matter circulation, which is driven by supernovae feedback say, and then became smooth in the core and fitted our observations best [ https://astrobites.org/2015/06/12/the-labor-of-outflows-against-dark-matter-halo/ ].

    More surprising is the large clump size cut off. Observations of clump distributions in galactic strong lensing has spoken of “structures ranging from hundreds of thousands of times the mass of the Milky Way galaxy to clumps no more massive than the heft of a commercial airplane.” [ https://www.nasa.gov/feature/goddard/2020/hubble-detects-smallest-known-dark-matter-clumps ].

    Also the article is ill written. The “apart from the gamma radiation they emit in exceptional circumstances” is only in their WIMP dark matter annihilation model of “some theories, they are converted into a burst of energetic gamma-ray radiation.” While on that topic, mind that Fermi-LAT, that observed center halo gamma radiation, just the other week rejected the likeliest natural WIMP mass range (1-300 GeV) [ https://scitechdaily.com/dark-matter-destruction-ruled-out-as-origin-of-extra-radiation-in-milky-ways-galactic-center/ ].

  6. … Sometimes it is not about knowing and not knowing, it can be about a will to accept that something is, what it is.
    For an example, theories are the theories that hold true 100% or they don’t hold.
    YO habe: entanglement, black wholes and quantum scale for Albert….

  7. … and when it comes to dark matter it is simple>
    1. It exists.
    2. It doesn’t exist.
    Well, if it exists: what is it, how it works, etc…
    On the other hand, if it doesn’t exist, what is causing that effects?

    Probability… 50% vs 50%… No, it is just 100%, but which way?…

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