Abell 2744 Is The Rumble Pit Where Four Galaxies Centers Are Colliding.

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Meet  Abell 2744. It is the sexy point in the Universe where four enormous cosmic entities are colliding. You’re staring at trillions of solar masses smashing into one another. Pretty, innit?

Bad Astronomy:

First off, this picture is a combination of observations from Hubble (in visible light, colored blue, green, and red), the Very Large Telescope (also blue, green, and red), and the Chandra X-Ray Observatory (X-rays, colored pinkish). In visible light you can see literally hundreds of galaxies, probably more, dotting the supercluster. The pink glow is from very hot gas between galaxies; it started its life as gas inside of galaxies that got stripped off and heated to millions of degrees as the galaxies plow through the space around them (I like to think of it as opening a car window to let a noxious smell out – the wind from the car’s motion pushes the air inside the car out the windows).

The blue glow is perhaps the most interesting bit here: it’s a map of the location of dark matter. This type of exotic matter neither emits nor reflects light – hence the name – but it has mass, and that means it has gravity. As I described when this method was used to trace dark matter in the Bullet Cluster, gravity bends space, and light follows that curve. Galaxies farther away get their light distorted by the gravity from dark matter, and that distortion can be measured and used to trace the location of dark matter. The blue glow in the image above maps that.

The thing about dark matter is that it doesn’t interact with normal matter (electron, protons, you, me, lip balm, oranges, whatever). But all that gas between galaxies shown in pink is normal matter, so when one galaxy cluster slams into another at a few thousand kilometers per second that gas gets compressed, mixed-up, and heated. But dark matter just blows right on through. So by comparing the location of the galaxies, the dark matter, and the hot gas, a lot of the cluster’s history can be unraveled.

Insane, no? Read the rest right here.