Cepheid Variables and the Cosmic Distance Scale
I.
Purpose
:
The purpose of the Cepheid Variables and Cosmic Distance scale lab is to determine
the distances to distant stars. By knowing all of the stars in the Small Magnetic Cloud
are the same distance from the sun, we learned that the brighter Cepheid’s are
intrinsically more luminous. Basically, the period of a Cepheid is an indicator of
intrinsic luminosity.
II.
Procedure
:
First, we used page 53 where we were given four Cepheid variables in the Small
Magnetic Cloud, taken using yellow light by Halton C. Arp. We started by finding
each stars maximum and minimum apparent magnitudes to the nearest 0.1 magnitude;
we then took the average of the two. We then had to find the period in days for each,
and we did this by taking the interval between peak to peak on the graph, also known
as successive maxima. We then used the logarithm of the period. Next, using the
graph paper provided we split the stars apparent magnitude as the ordinate against the
logarithm of the period, to two decimal places. On the graph on page 56 we then
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 Spring '10
 Reim
 cepheid variables, Cepheid, cosmic distance scale, Small Magnetic Cloud

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