W Virginis variable
From Free net encyclopedia
A W Virginis variable is a variable star similar to a Cepheid variable. However, using the same formula to calculate its distance will yield a value that is too small, a mistake that Edwin Hubble made while observing M31.
W Virginis are different because they are population II stars, and so have a lower mass (less than our Sun), and lower metallicity. Their luminosity is, on average, about 1.5 magnitudes less than classical Cepheids. The period varies between 1 and 60 days.
W Virginis are also called Type II Cepheids.
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