Dr Giovanni Carraro, (European Southern Observatory):
How well do we know the spiral structure of our own Galaxy?
A large Macarthur Astronomy Society audience gave a big welcome this month to the first of our February Double Whammy speakers, Giovanni Carraro:
Giovanni was in Australia for a month as part of the AAO Distinguished Visitor Proramme. He is an astronomer at La Silla Paranal Observatory in Chile. His interests are in star clusters as probes of Galactic structure and evolution and he is officially here to work on "high resolution optical spectroscopy of old star clusters and to measure detailed chemical abundances and constrain the formation history of these clusters relative to their environment in the Milky Way Galaxy".
His talk, titled: "How well do we know the spiral structure of our own Galaxy?" was enlightening, because the answer is that, unlike other nearby galaxies, we still know relatively little about the structure of our own Milky Way galaxy. Why? Because we live inside it!
Giovanni showed us a series of detailed line diagrams which show the history of research into the Milky Way structure over recent decades and described how difficult it is to see through the gas and dust which make up our galaxy.
Early mapping
Step by step, using the entire spectrum of electro-magnetic wavelengths, astronomers have been piecing together a map of the galactic structure. However, whilst Giovanni's final slide showed just how much headway is being made, that there is still considerable work left to be done!
Newly discovered structures (yellow and white).
This was an inspiring but very detailed talk by Giovanni and I wish I had taken notes as well as imaging some of his slides. I wish I could hear him give this talk a second time.....
Question time at the end of the talk was lively and Giovanni confimed in answer to my own question that the speed of the stars around the galaxy is independent of the speed of the spiral arms themselves. This is very intriguing because we tend to perceive the stars which form the structure spiral arms as moving in unison with the arms.
John Rombi asks a question.
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