Galactic Archaeology

On Friday 30th September Marlborough was delighted to welcome Dr Payel Das from Oxford University for a Science Department Talk.

Dr Das began to specialise in astrophysics from her fourth year at Oxford and obtained her PhD through her thesis into orbital structures and dark matter distributions within the outer regions of elliptical galaxies. She is now working as a postdoctoral research assistant and undergraduate tutor.

The seminar of the evening, aptly entitled “Galactic Archaeology”, sought to give the physics and astronomy students at Marlborough an overview of how the study of archaeology may be transferred to the cosmos. This field enables physicists to build an accurate physical description of our stellar landscape and ultimately secure a deeper insight into the systems and structures by which such a landscape would have evolved. Naturally such a branch of archaeology would assume much grander scales and have more profound implications.

Dr Das spiritedly began by placing these studies in context, describing how dark matter coalescence corresponds to denser, hotter regions of gas that will eventually birth stars. Under the force of gravity these stars will pool together to form a galaxy, of which the centre is inevitably the oldest part. Such a galaxy is typically elliptical in shape but collisions often induce the formation of spiral arms, our Milky Way being a prime example.

Our speaker continued to guide us through the derivation of formulae for stellar luminosities, surface temperatures and radii; emission spectroscopy also featured in the calculation of elemental abundances of a given star. With such data we may model for stellar age and mass, greatly improving our depiction of the astronomical landscape. Using the Doppler effect to determine relative velocity along our line of sight, and stellar parallax for the distance of nearby stars, orbital structure and crucially dark matter mass of any given galaxy may also be deduced if the positions and plane velocities of the stars are known.

Dr Das illustrated these apparently enigmatic concepts beautifully. The unwavering engagement of the audience could be attributed to her superb use of media and flair for teaching. Her responses to the questions posed at the end of the talk were delivered with equal fluency and throughout the talk she demonstrated a connection to her field of study that the students at Marlborough should strive to parallel in their chosen career. We wish Dr Das all the best for the future and send our deep thanks to her for taking the time to give us a thoroughly enjoyable and thought-provoking evening.

Molly Gibbins (CO L6)

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