For a bit of 2010 and a lot of 2011, I had the great pleasure of leading a couple of students through some real astronomical research. This is actually something I have been doing quite a lot, but these two guys, Josh and Tom, were a couple of the first, but far from the last! They originally chose to do an independent research project for their HSC (Higher School Certificate – Yr 11 & 12) on astronomy, so their teacher, Sandra, got me in to give them a run down of what they could do. What we ended up looking at was a group of pulsating stars called RR Lyraes in a globular cluster, with the prosaic name, NGC6101… which is basically just a catalogue number. What was particularly interesting was that, while these stars had been identified in the 1970s, nobody had really looked at them at all until the students did! So what did they actually do? Well first they took images of the cluster over a series of a couple of months to measure these stars ‘twinkling’. The following image is from APOD, and shows how these stars ‘twinkle’ over time.

They twinkle because they are ‘pulsating’, over time they get bigger and smaller due to their instability. When they are small the light generated by the core of the star cannot pass easily through outer shells of the star, so it pushes these shells out causing the star to expand. Eventually, once it is bigger and less dense, the light all of the sudden can get through and the shells get pulled back in by gravity to where it began, ultimately to repeat itself over… and over… and over. A single pulsation happens over the course of less than a day (usually much less!) so this is quite a rapid process! You can actually measure this brightness change over time for each of the stars to get a handle on how they are pulsating… making graphs like below… where up is brighter, down is dimmer and the left/right axis is time….. sorta! Its actually ‘phase’ but ‘time’ works well enough to get whats going on… so they are getting brighter and dimmer over time.

The particularly useful thing about these stars is that they are ‘standard candles’, which means because they are this particular type of star, we can know if they pulsate in a particular way, then we know roughly how bright they should be. By comparing how bright they should be to how bright they actually appear, we can actually measure distance, which formed a significant fraction of what the students undertook in their research. A significant result of this research was an independant measure of the distance to this globular cluster, which gelled and gave strength to previous estimates using different methods. This is particularly important as distance in astronomy is actually quite tricky to measure, and we use all sorts of cunning schemes to measure it, so it is best to measure it in as many ways as possible! And, of course, far from the least achievement in astronomy is the imagery…. so please take a moment to bask in the image of NGC6101 made from our Blue, Green and Infrared images below.

Anyhow, over the course of the last year I took their initial report and their data and their conclusions, and after dealing with a LOT of the more tedious science-y stuff you need to do, like checks and balances and comparisons to previous literatures and some deep thought about how best not to look like an idiot in print, we submitted a proper scientific paper, and it got published in December 2011! Woohoo! A lot of the intervening time, and a lot of the delay in posting about this, has been due to getting ready, and correct (and idiot-free) another, quite substantially larger, paper ready to submit, which I should do this week! Theres also a flurry of other occurances around the corner, and lots to try and fit into my 9am-10pm mega-PhD worklife, but its all quite lovely and grand! While you are waiting, you can check out our emergences (and my apparent, but not real, shortness) into a couple of newsletters here and here. Enjoy comrades.