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Paper: SETI and the Galactic Belt of Intelligent Life
Volume: 213, Bioastronomy '99: A New Era in Bioastronomy
Page: 441
Authors: Balázs, Béla
Abstract: The gravitational density wave theory of Lin and his co-workers involves the formation of stars along a rather concentrated shock front which co-rotates with the spiral pattern as a rigid body around the galactic center. The locus of star formation is expected to move according to the pattern velocity which -- in view of the differential rotation of the Galaxy -- generally departs from the circular velocity of stars nd interstellar clouds (expect at a critical distance from the center: at the co-rotation radius) and thus one could expect to find systematic effects in the shifts of spiral arm tracers of different ages. If we assume that the case of mankind is about average and accept the idea that the longevity of a civilization might be limited with high probability by catastrophic events, threatening during the crossing of the galactic arms, intelligent life is presumably concentrated on a belt in the Galaxy which is a narrow annulus including the co-rotation circle and the galactic orbit of our sun. If the ``Galactic Belt of Intelligent Life'' is a reality at least the first and last factors in the 'Drake Equation' must be reassessed. From heliocentric point of view the distribution of our potential extraterrestrial partners is highly anisotropic: in a small solid angle around the line of sight there are about thousand times as many of them in the tangential directions than towards the galactic center or anticenter.
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