ESO Science Release | VLT | MUSE | 2015 Apr 14
Dark matter may not be completely dark after all
Using the MUSE instrument on ESO’s VLT in Chile, along with images from Hubble in orbit, a team of astronomers studied the simultaneous collision of four galaxies in the galaxy cluster Abell 3827. The team could trace out where the mass lies within the system and compare the distribution of the dark matter with the positions of the luminous galaxies.
Although dark matter cannot be seen, the team could deduce its location using a technique called gravitational lensing. The collision happened to take place directly in front of a much more distant, unrelated source. The mass of dark matter around the colliding galaxies severely distorted spacetime, deviating the path of light rays coming from the distant background galaxy — and distorting its image into characteristic arc shapes.
Our current understanding is that all galaxies exist inside clumps of dark matter. Without the constraining effect of dark matter’s gravity, galaxies like the Milky Way would fling themselves apart as they rotate. In order to prevent this, 85 percent of the Universe’s mass must exist as dark matter, and yet its true nature remains a mystery. ...
First potential signs of “interacting” dark matter suggest it is not completely dark after all
Durham University UK | 2015 Apr 14
The behaviour of dark matter associated with four bright cluster galaxies in the 10 kpc core of Abell 3827 - Richard Massey et al