I’m currently sitting in the Young Astronomers’ Session at NAM, coming to terms once again with the fact that I’m not really a young astronomer any more. Although PhD students present their work throughout the week, this is an extra opportunity to hear about the best work from a wide range of people.  As an example, the current speaker is Iraklis Konstantopoulous from UCL; it was inevitable I’d write about this topic because M82 is one of my favourite objects in the entire sky.  

 
M82 from HST (colour) and WIYN H-alpha showing galactic wind (pink)

As you can see, it’s an edge on spiral with lots of star formation, which is driving in turn the dramatic wind you can see. Iraklis & co have been studying star clusters in the galaxy; while they’re interesting in themselves they also contain information about the galaxy itself. For example, a large region of the galaxy appears to have fewer clusters than it should do.To understand this, you have to think about how M82 would look from elsewhere in the Universe. In fact, we have to consider what M82 would look like when viewed edge on. We need a galaxy with two prominent spiral arms, and a dominant bar. Rather like this one

NGC 1365 as seen by the Very Large Telescope

Now imagine viewing this galaxy from the bottom of the picture. On the right, you’ll see material ‘behind’ the spiral arm blocked by dust contained within the arm; hence the lack of clusters here. On the left, we see directly to the spiral arm, and this is where many clusters are found lurking. The best bit is that we can check this hypothesis by looking at the relative velocity of the clusters; and Iraklis does indeed find that clusters on the left are moving at a different speed to those on the right.The conclusion? Maybe M82 isn’t so weird after all…