We had a fantastic production meeting yesterday morning, and I’m really looking forward to the rest of the year. We also had a quick rundown of what we’ve missed in the two months without news notes, and I was generally mocked for suggesting that NASA’s announcement on dark matter yesterday was likely to be interesting.
I was right. Here’s what they’ve done. Take this image of a cluster of galaxies:
Then spend a long time looking at the shapes of all the small background galaxies, looking for the distortion caused by the passage of their light through the massive foreground galaxy cluster. Then use those distortions to work out where the mass is in the cluster – not just the mass that happens to shine, but all the dark matter too. Colour the result a pretty shade of blue.
The first thing you notice is that it really is a very nice shade of blue, and that NASA’s graphics are getting better and better. Then you notice that the matter in the cluster forms a ring around the centre. This is a slightly crazy result, and the astronomers involved spent a year refusing to believe their eyes (or slightly more accurately, their computers). What seems to have happened is that this is a collision between two clusters, which we’re viewing head-on. The ring is a ripple moving outwards as an aftershock of the collision. There’s a simulation of this here, or you can look at high resolution images (and non-quicktime movies) here.
It’s a stunning result, and the observers deserve a huge amount of credit for what must have been a massive (pun intended) amount of work. But I’m not sure this quote, from first author Myungkook James Jee, is correct
“This is the first time we have detected dark matter as having a unique structure that is different from the gas and galaxies in the cluster”