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Author Topic: How do we know whether a star has a red or blue spectrum shift ?  (Read 1797 times)

Offline bizerl

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In regards to the red shift and blue shift of stars to measure their movement away or towards us: If the only information we have to recognise distant stars is the light emitted by them, how do we know that the red shift or blue shift isnít just the colour of the star and not due to movement? How do scientists find the value from which to measure the Doppler shift?


 

Offline RD

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... how do we know that the red shift or blue shift isnít just the colour of the star and not due to movement?

Within the light spectrum from the star are dark absorption lines which are a bit like a barcode for specific elements ...



The extent to which this barcode is shifted compared with the reference spectrum of the same element on Earth will tell you whether the star is red or blue shifted due to its motion.
« Last Edit: 17/07/2012 04:10:46 by RD »
 

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