Mergers and Acquisitions

A cosmic kaleidoscopeThis multi-colored haze is actually two colliding galaxy clusters that are forming a single object known as MACS J0416.1-2403 (or MACS J0416 for short). It’s located about 4.3 billion light-years from Earth. This image combines data from three different telescopes: the Hubble Space Telescope (showing the galaxies and stars), the Chandra X-ray Observatory (diffuse emission in blue), and the NRAO Very Large Array (diffuse emission in pink). Each telescope shows a different element of the cluster.

As with all galaxy clusters, MACS J0416 contains a significant amount of dark matter which leaves a detectable imprint in visible light by distorting the images of background galaxies. In this image the dark matter appears to align well with the blue-hued hot gas, suggesting that the two clusters have not yet collided. If the clusters had already merged, the dark matter and gas would have separated.

Image credit: NASA / ESA / CXC / NRAO-AUI-NSF /STScI / G. Ogrean (Stanford University)

WIMPy X-rays

gcenterbump_fermi_960The picture on the left is a raw image of the x-rays detected by the Fermi Gamma-ray Space Telescope looking toward the center of the galaxy. The image on the right is same data with the known sources subtracted. Where are the excess x-rays coming from?

One controversial hypothesis that seems to explain the data involves a type of dark matter known as WIMPs colliding with themselves to create the detected gamma-rays. Finding the nature of dark matter is one of the great quests of modern science, and this type of cosmologically pervasive matter has shown itself thus far only through gravitation.

Image Credit: NASA

Seeing Dark Matter

dark_matterWell, sorta/kinda … This composite image of Hubble Space Telescope observations shows a ghostly “ring” of dark matter in the galaxy cluster Cl 0024+17. The ring-like structure is noticeable in the blue map of the cluster’s dark matter distribution superimposed on a Hubble image of the cluster. The map was derived from Hubble observations of how the gravity of the cluster Cl 0024+17 distorts the light of more distant galaxies via a process know as gravitational lensing. We can’t see dark matter, but its existence can be inferred by mapping the distorted shapes of the background galaxies, showing how dark matter is distributed in the cluster.

It’s been suggested that the dark matter ring was produced from a collision between two gigantic clusters. Dark matter makes up the bulk of the universe’s material and is believed to make up the underlying structure of the cosmos.

Image Credit: NASA