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The Prayer Circle

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Antapex [WORK]


We exploit recent theoretical advances toward the origin and orbital evolution of comets and asteroids to obtain revised estimates for cratering rates in the jovian system. We find that most, probably more than 90%, of the craters on the Galilean satellites are caused by the impact of Jupiter-family comets (JFCs). These are comets with short periods, in generally low-inclination orbits, whose dynamics are dominated by Jupiter. Nearly isotropic comets (long period and Halley-type) contribute at the 1-10% level. Trojan asteroids might also be important at the 1-10% level; if they are important, they would be especially important for smaller craters. Main belt asteroids are currently unimportant, as each 20-km crater made on Ganymede implies the disruption of a 200-km diameter parental asteroid, a destruction rate far beyond the resources of today's asteroid belt. Twenty-kilometer diameter craters are made by kilometer-size impactors; such events occur on a Galilean satellite about once in a million years. The paucity of 20-km craters on Europa indicates that its surface is of order 10 Ma. Lightly cratered surfaces on Ganymede are nominally of order 0.5-1.0 Ga. The uncertainty in these estimates is about a factor of five. Callisto is old, probably more than 4 Ga. It is too heavily cratered to be accounted for by the current flux of JFCs. The lack of pronounced apex-antapex asymmetries on Ganymede may be compatible with crater equilibrium, but it is more easily understood as evidence for nonsynchronous rotation of an icy carapace.




antapex



An analysis of sporadic meteor flux distributions over the celestial sphere is given. Symmetry of the radiant distribution relative to the plane crossing the ecliptic pole and the Earth's apex and antapex was identified.


In this work we perform a numerical study of the collision distribution on the Lunar surface for a set of 251780 trajectories in the Earth-Moon circular restricted three body problem, for a value h=-1.585 of the Jacobi constant. Different from others papers, we obtain an asymmetrical equatorial distribution of impacts that get a maximum value in a close direction to antapex and shows a large region without collisions. FULL TEXT IN SPANISH


We use Tully--Fisher distances for a sample of late type, field spiral galaxies to test the Lauer and Postman (1994;LP) result suggestive of a bulk flow with respect to the Cosmic Microwave Background reference frame, of amplitude of +689 km s(-1) in the direction l=343(deg) , b=+52(deg) , and extending to very large spatial scales. A total of 268 galaxies, subdivided between two cones of one steradian each and pointed respectively toward the apex and antapex of the LP motion, are used. The peculiar velocities of the two data sets are inconsistent with a bulk flow of the amplitude claimed by LP. 041b061a72


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