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(Redirected from Cyranus Galaxy)
Opinion is divided whether the Colonies lie in the same galaxy as Earth, which—given numerous references (particularly in "Greetings from Earth") that the Earth sought after by the Colonials is our Earth—would have to be identical to our "Milky Way galaxy".
Proponents of the identity of the two galaxies argue that it is less improbable that the Fleet could traverse a large span of several thousand light-years within the Milky Way galaxy (which is approximately 100,000 light-years in diameter) than to make a journey from one galaxy to another (which implies a journey of two million light-years or more).
Note, however, that both explanations automatically assume that the "galaxy" term means the same thing to the Colonials as it does to us, i.e. a massive system of millions or billions of individual star systems orbiting a common center of mass. This is not necessarily the case (see e.g. micron and parsec). Statements such as "[Earth's] proximity to the sun provides the only climate in the galaxy comfortably able to support life as we know it" (Galactica Discovers Earth, Part I) suggests a colonial "galaxy" may in fact be the same thing as a star/solar system. Thus the Cyrannus "galaxy" may in fact consist only of a handful of stars and planets orbiting each other, broadly similar to our own solar system.
In the spin-off series Galactica 1980, the Fleet reaches 30 years after the Battle of Cimtar. The Original Series does not define the nature of propulsion nor does it provide sufficient information to determine if intergalactic travel is in use.