How do We Know the Distance to the Stars?

(Starts With A Bang!) – Ethan Siegel:

Today, our understanding of the expanding Universe depends extraordinarily precisely on measuring cosmic distances. Yet the closest rungs on that cosmic distance ladder, for stars like Cepheid variables within our own galaxy, are dependent on the parallax method. If there’s an error of just a few percent on those measurements, then those errors will propagate all the way to the greatest distances, and this is one potential resolution to the tensions in the measurements of the Hubble constant. We’ve come a long way in measuring cosmic distances to an incredible precision, but we’re not 100% certain that our best methods are as accurate as we need them to be. Perhaps, after four centuries of trying to measure how far away the nearest stars truly are, we still have farther to go. …

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Stellar parallax

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