re: HARPS measures the motion of our Milky Way
The astronomers found that the deviations in the measured velocity of Cepheids were linked to the chemical elements in the atmospheres of the Cepheids considered. "This result, if generalised to all Cepheids, implies that the rotation of the Milky Way is simpler than previously thought, and is certainly symmetrical about an axis," concludes Nardetto.
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Once again the standard candles are more complex than thought. I wonder if this apparent Cepheid motion correction will impart a slight tweak to the Hubble constant and distance scale.