The Astrology of Space - Matrix Software

The Astrology of Space
The RR Lyrae Stars
RR Lyrae stars were first known as Cluster-type
Variables, since they were discovered (in large
numbers) in the high velocity globular clusters. RR
Lyrae stars have absolute magnitudes near zero and
spectral types near class A5. These stars are
pulsating stars of very short period (usually less than
one day) and only a slight dependence exists
between period and luminosity, unlike the Cepheids.
RR Lyrae stars (named after the star RR Lyrae, one
of the brightest in this group) are very numerous in
our galaxy, but are too faint to be seen in any but the
nearest of the external galaxies. Some have been
observed in the dwarf system in Sculptor and the
Magellanic Clouds. RR Lyrae stars posses a high
velocity motion that associates them with objects in
the nucleus of our galaxy and other dust-free regions
of space. As mentioned, they were first discovered in
large numbers in globular clusters, which are very old
and relatively free of interstellar dust.
W. Virginis and RV Tauri Stars
W Virginis and RV Tauri stars have periods of more
than a day to over a hundred days. This group spans
the range between the RR Lyrae stars and the longperiod
variables. These stars all occur in globular
clusters (as do the RR Lyrae stars) and are often
called Type II Cepheids. They have a spectral class of
F to 6, but display strong bright lines of hydrogen. The
group of shortest period is called the RV Tauri stars,
after a typical specimen while those having periods
between ten and thirty days are W Virginis stars.
Whereas all the classical Cepheids are found in the
galactic plane (within the layer of dust and gas), the
type II Cepheids occur at large distances from the
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