GALAH Survey

The Galactic Archaeology with HERMES (GALAH) Survey is an ambitious project using the AAT's new HERMES spectrograph to observe a million stars in our Milky Way Galaxy. The HERMES spectrograph is fed by the 2dF fibre optic positioner system which allows exquisitely detailed measurements to be made on 400 stars at a time.

The GALAH project aims to understand to what extent the galactic disk’s composition is from stars that originated in other galaxies and later merged with the Milky Way Galaxy, and what drove the major episodes of star formation in the Galaxy's disk. The goal of GALAH is to map out substructures of the early Milky Way galaxy in order to gain a clearer idea of how our Galaxy formed and evolved. 

But how can you tell if a star is from our galaxy, or from a merger event? Stars have something similar to a DNA profile, namely their elemental abundances. By exploring a star’s chemical state, we gain information on what kind of gas the star must have formed from. This method, known as chemical tagging, allows us to detect whether a star formed within the galaxy, or was accreted from a satellite galaxy.

HERMES can observe in four wavelength bands simultaneously, and these bandwidths have been tailored to maximize the number of chemical element lines captured. For each star, GALAH will provide an accurate velocity and 25 chemical signatures, allowing astronomers to trace the growth of our beautiful but cannibalistic Galaxy with unprecedented accuracy.

Lew, Tony and Jeroen in front of the HERMES instrument

Lew, Tony and Jeroen in front of the HERMES instrument, used in the GALAH survey. Image: AAO

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