Another day, another sunset.

M33 Spiral Galaxy - Scaled!
Originally uploaded by Astro Guy.

The image above was probably the first really cool astronomy picture that I made. My masters research was a carbon star survery of the nearby galaxy M33. Carbon stars are evolved stars that are burning Helium near their cores (shell burning) instead of hydrogen core burning (like our Sun does). Normally these stars are called AGB stars have have atmospheres that are chemically dominated by an abundance of oxygen after the formation of carbon-monoxide. Sometimes, a AGB star will form a double shell energy source with the addition of a hydrogen burning shell. Having to heat sources at different radii from the centre of the star is thermally imbalanced. The star comes almost complete convective and carbon rich material from the core of the star (formed by fusing helium) is transported to the surface of the star. This excess of carbon alters the chemistry of the atmosphere to a carbon dominated state. So in an Oxygen dominated atmosphere (M-star) one can see the formation of molecules such as TiO, whereas in a Carbon dominated atmosphere molecular species such as CN are present. Each of these molecules absorps light at different wavelenghts cause observationally different spectra to be observed.

So, one can build a set of narrow band filters to distinguish between an M-star and C-star. My masters project was to map this ratio around the disc of the nearby (800 Mpc) galaxy M33. It's about the same distance away from us as the Andromedia galaxy (M31). The ratio of C-stars to M-stars (C/M ratio) is a good tracer of the initial metal content of the star. A population of stars formed from metal poor gas is more efficient at forming C-stars than metal rich gas. So we have a tracer of the metallicity of the galaxy and a peak at the history of star formation in a galaxy. All in all, I found about ten thousand C-stars out of 1.3 million stars. It was a lot of work, but we got our result, and I got to make this cool picture from all the data in the end!

and now.. another garbled song...

Time, time, time, sees, what from me it became during I am around
approximate after my possibilities that I was hard therefore with
please however volatile view around, the pages brown looked and the
sky is nebulous nuance of the winter