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The Question

(Submitted April 22, 2006)

How does the discovery of Polaris being a binary star affect our thoughts on cepheid variable stars, and how will it help us discover more about the size and growth of our universe?

The Answer

Thanks for your question. Polaris is believed to be a special type of Cepheid in which it is pulsating at its first overtone mode with more than one node of pulsation within the star. Since Polaris has companion stars, the minute changes in Polaris' orbit caused by the interaction with the companion stars gives a measure of the mass of Polaris --which can be used independently to better understand the physics of Cepheid behavior of Polaris. You might want to read more at the following website:
http://www.astro.uiuc.edu/~kaler/sow/polaris.html

Understanding Cepheids in better detail will help to better delineate Cepheids as Standard Candles, ie, objects in space that can be used to measure distances and knowing distance scales better will help us to understand how the universe is growing. You can read about the distance ladder at:
http://heasarc.gsfc.nasa.gov/docs/cosmic/

Hope this helps,
Georgia & Mike
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