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The slow interaction of dark matter


For the first time, the dark matter may have been observed in interaction with other dark matter in a different way by the gravitational attraction. The observation of colliding galaxies carried out with the VLT (Very Large Telescope) ESO and the Hubble Space Telescope NASA / ESA has permission to collect the first interesting clues about the nature of this mysterious component of the Universe.
For the first time the dark matter may have been observed in interaction with other dark matter in a different way by the gravitational attraction. The observation of colliding galaxies carried out with the VLT (Very Large Telescope) ESO and the Hubble Space Telescope NASA / ESA has permission to collect the first interesting clues about the nature of this mysterious component of the Universe. In fact, using the instrument MUSE installed on ESO’s VLT in Chile, along with images of the Hubble orbiting telescope, a team of astronomers studied the simultaneous collision of four galaxies in the cluster of galaxies Abell 3827. The team was able to trace the ‘location of the mass within the system and compare the distribution of dark matter with the position of the bright galaxies.

Hubble image of galaxy cluster Abell 3827 showing dark matter di

Credit: Hubble Space Telescope

Although dark matter can not be seen, the team was able to deduce the location using a technique called gravitational lensing. The collision occurred by chance right in front of a source much more distant and unrelated. The mass of dark matter around galaxies in collision has distorted the space-time, diverting the path of the rays of light coming from distant background galaxy – and distorting the image in features curved shapes.
The current theory is that all galaxies are formed inside clumps of dark matter. Without the binding effect of the gravity of the dark matter, galaxies like the Milky Way would go to pieces in the rotation. To avoid this, 85% of the mass of the Universe must exist in the form of dark matter, but its true nature remains mysterious.
In this study, the researchers observed the four interacting galaxies and found that a lump of dark matter was apparently left behind the surrounding galaxy. Dark matter is now at about 5,000 light years (50 000 million million miles) behind the galaxy – the Voyager spacecraft NASA would take 90 million years to cover this distance.
A delay between the dark matter and galaxy associated with it is expected during the collision if the dark matter interacts with itself, although weakly, due to forces other than gravity. Dark matter has never been observed before interact differently by the force of gravity.
The first author Richard Massey of Durham University explains: “We used to think that the same dark matter there quiet, looking only to itself, except for the gravitational attraction. But if the dark matter was slowed down during the collision, may be the first evidence of a different physical area dark – the hidden universe around us. ”
This result derives from another recently this same team, who observed 72 clashes between clusters of galaxies and found that dark matter interacts very little with herself. The new work instead concerns the motion of individual galaxies, instead of galaxy clusters. The researchers argue that the clash between these galaxies could have lasted longer than the collision observed in the previous study – allowing the effects of a minimum of friction force also grow over time and produce a measurable delay.
Taken together, these two results shrink for the first time the possible behavior of dark matter “dark matter interacts more than that, but less than that. Massey added: “We are finally forcing the dark matter corner, pushing our knowledge from two different directions.”
This research was presented in an article entitled “The behavior of dark matter associated with 4 bright cluster galaxies located in the 10 kpc core of Abell 3827” which was published on Monthly Notices of the Royal Astronomical Society in April 15, 2015.

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