Monday, December 31, 2018

astronomy - How is distance measured to far away stars and galaxies?



What I need is an accurate description of the methods used to determine the distance to Andromeda. The Parallax method is for nearby objects as I presume. The red shift method applies, but how do you really determine a red shift? Maybe the radiation emanated from that object already has the wave lengths reach Earth? Or maybe it's travelling at a large speed from us? Or maybe its mass is greater than we think?



Answer



The parallax method is shorter than required for Andromeda and the red shift method is longer, than required for it.


The distance to Andromeda galaxy is measured by the method of standard candles: http://en.wikipedia.org/wiki/Standard_candle#Standard_candles


I think Cepheid variable starts are appropriate for Andromeda galaxy. The period of pulsing of those stars is related with it's maximal brightness, which allows to calculate the distance.


http://www.physlink.com/education/askexperts/ae589.cfm


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