* Astronomy

Blobrana · L

RE: Dark matter

Blobrana · L

Earth Might Have Hairy Dark Matter

A new study publishing this week in the Astrophysical Journal by Gary Prézeau of NASA's Jet Propulsion Laboratory, Pasadena, California, proposes the existence of long filaments of dark matter, or "hairs."
According to calculations done in the 1990s and simulations performed in the last decade, dark matter forms "fine-grained streams" of particles that move at the same velocity and orbit galaxies such as ours.
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Title: Weighing of the Dark Matter at the Center of the Galaxy
Author: V. I. Dokuchaev, Yu. N. Eroshenko

A promising method for measuring the total mass of the dark matter near a supermassive black hole at the center of the Galaxy based on observations of nonrelativistic precession of the orbits of fast S0 stars together with constraints on the annihilation signal from the dark matter particles has been discussed. An analytical expression for the precession angle has been obtained under the assumption of a power-law profile of the dark matter density. In the near future, modern telescopes will be able to measure the precession of the orbits of S0 stars or to obtain a strong bound on it. The mass of the dark matter necessary for the explanation of the observed excess of gamma radiation owing to the annihilation of the dark matter particles has been calculated with allowance for the Sommerfeld effect.

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Deep space images shed light on dark matter

The images are the first from an international collaboration, involving Durham University, which is seeking to understand the amount of dark matter in the Universe and its distribution in groups of galaxies - such as the group that houses the Milky Way.
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Title: Is it possible to discover a dark matter particle with an accelerator?
Author: Vadim A. Bednyakov

The paper contains description of the main properties of the galactic dark matter (DM) particles, available approaches for detection of DM, main features of direct DM detection, ways to estimate prospects for the DM detection, the first collider search for a DM candidate within an Effective Field Theory, complete review of ATLAS results of the DM candidate search with LHC RUN I, and less complete review of "exotic" dark particle searches with other accelerators and not only. From these considerations it follows that one is unable to prove, especially model-independently,a discovery of a DM particle with an accelerator, or collider. One can only obtain evidence on existence of a weakly interacting neutral particle, which could be, or could not be the DM candidate. The current LHC DM search program uses only the missing transverse energy signature. Non-observation of any excess above Standard Model expectations forces the LHC experiments to enter into the same fighting for the best exclusion curve, in which (almost) all direct and indirect DM search experiments permanently take place. But this fighting has very little (almost nothing) to do with a real possibility of discovering a DM particle. The true DM particles possess an exclusive galactic signature --- annual modulation of a signal, which is accessible today only for direct DM detection experiments. There is no way for it with a collider, or accelerator. Therefore to prove the DM nature of a collider-discovered candidate one must find the candidate in a direct DM experiment and demonstrate the galactic signature for the candidate. Furthermore, being observed, the DM particle must be implemented into a modern theoretical framework. The best candidate is the supersymmetry, which looks today inevitable for coherent interpretation of all available DM data.

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How does new dark matter evidence fit together?

In recent weeks there have been an unprecedented number of papers on dark matter in such a short time.
They comprise new gravitational lensing experiments that have mapped dark matter on a range of scales.
These all use similar methods, but vary in terms of resolution and size. Similar to the art of making maps on Earth this "skotocartography" tells us different but complementary things about the nature of dark matter.
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Dark matter becomes less 'ghostly'

A team of astronomers led by Dr Richard Massey of Durham University studied a simultaneous collision of four galaxies in the cluster Abell 3827.
Although dark matter cannot be seen, the team was able to deduce its location using a technique called gravitational lensing. While dark matter does not absorb or emit light, it does have gravity.
So it bends the path of light passing nearby, warping our view of anything on the other side of it. The dark matter in Abell 3827 bent the path of light rays coming from a distant background galaxy, which happened to be aligned just right for the team's purpose.
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First potential signs of "interacting" dark matter suggest it is not completely dark after all

Astronomers believe they might have observed the first potential signs of dark matter interacting with a force other than gravity.
An international team of scientists, led by researchers at Durham University, UK, made the discovery by using the Hubble Space Telescope to view the simultaneous collision of four distant galaxies at the centre of a galaxy cluster 1.3 billion light years away from Earth.
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Dark matter map unveils first results

A huge effort to map dark matter across the cosmos has released its first data. Dark matter is the invisible "web" that holds galaxies together; by watching how clumps of it shift over time, scientists hope eventually to quantify dark energy - the even more mysterious force that is pushing the cosmos apart.
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Dark matter 'ghosts' through galactic smash-ups

By observing multiple collisions between huge clusters of galaxies, scientists have witnessed dark matter coasting straight through the turmoil.
Dark matter is the mysterious, invisible stuff that makes up 85% of the matter in the cosmos - and these results rule out several theoretical models put forward to explain it.
This is because it barely interacts with anything at all, including the dark matter in the oncoming galaxies.
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