
Cosmology standard candle not so standard after all - J3L2404
http://www.sciencedaily.com/releases/2011/01/110112143218.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily+%28ScienceDaily%3A+Latest+Science+News%29
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InclinedPlane
This happened before, the relationship between Cepheid luminosity and
variation period were worked out with nearby stars that we could measure
distance to via parallax. This relationship was used to determine the distance
to nearby galaxies and thus establish the basic foundation of the scale of the
Universe (e.g. determining the value of the Hubble constant, etc.) However, it
turns out there are actually two types of Cepheids and they do not have the
same relationship between period and luminosity. This meant that measurements
of distances to neighboring galaxies were wrong, since they included a mixture
of classical and Type II Cepheids. Fixing that error led to adjustments to the
estimated distance to neighboring galaxies by a factor of 4, and a comparable
increase in the age and size of the Universe. This solved a fundamental
problem at the time, whereby the Earth was older than the Universe (since we
can measure the age of the Earth via radiological dating of Uranium, for
example).

Note that today we have multiple methods for determining the age of the
Universe (such as type Ia supernovae, study of the cosmic microwave
background, etc.) so this revelation is unlikely to change that, though it's
likely to have other implications in our understanding of cosmology.

