Unknown Pleasures

I am part of the GALAH Survey, a project to observe hundreds of thousands of stars in the Milky Way to try and piece together its history. The project uses the HERMES spectrograph on the Might Anglo-Australian Telescope at Coonabarabran in central New South Wales. With this, we can observe almost 400 stars at the same time, and the light gets split into 4 seperate colour bands, from blue to infrared. GALAH recently had its Data Release 3, giving the data to everyone and anyone to play with.


There are 2.4 million spectra available. With this many spectra, what do you do? You recreate a classic album cover!


If you don't know the original, which used data from the recently destroyed Aricebo Telescope, check out this excellent article.


In the above, we have absorption lines due to the presence of various chemical elements in the atmospheres of the stars, with the big line in the middle being due to the presence of calcium. Why ain't they all lined up? Basically because the stars are moving with respect to each other. What you are seeing is the Doppler shift in action. How cool!

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