Another piece in the dark matter puzzle

The blue and red haze is the x-ray emission from the gas. The green contours represent the gravitational potential mapping the mass distribution in the cluster of galaxies. The authors looked at the the matter "blob" to the right of the yellowish gas front. This blob originally came from the left, and within some 100,000 years it moved through the larger blob to the left, where the gas was separated. Credit: Data from the Chandra x-ray telescope, courtesy of Signe Riemer-Sørensen.