Variable Stars Common Observation
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RS Puppis: the light echoes calibrate
standard candles for accurate distance measurements
by Ivan Adamin in March-April 2014 (#5)
Cepheids allow astronomers to measure vast distances across space. RS Puppis is an unusual cepheid embedded into an interstellar dust cloud illuminated by the variable light, enabling a phenomenon known as a light echo to be observed in details. Sparks (1994) showed that the polarization of a light echo can be used to measure its distance geometrically. This approach was used to determine the distance to RS Puppis with great accuracy, and hence calibrate the cosmic distance scale, based on the period-luminosity relation of classical Cepheid variables.
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