Optical thickness of the Cassini division

Various estimates for the optical thickness of the Cassini division are studied in order to explain and eliminate the discrepancies between them. An analysis of dark-side observations and a theoretical study based on the behavior of collisions suggest that the optical thickness of the Cassini division is not constant, but fluctuates in the range of 10^?4–10^?3. The nonzero brightness in reflected light is caused either by stray light or by narrow optically thick ringlets inside the Cassini division.     

Über die Lokalisierung von Wismut in Gesteinen mit Kernemulsionsplatten

Zusammenfassung Die Methode der Lokalisierung von Bi in Gesteinen mittels der -Strahlung von künstlichem Po, das durch die Reaktion Bi²⁰⁹ (n, ) RaE durch Bestrahlung mit thermischen Neutronen in einem Uranpile erzeugt wird, wurde an einem Gesteinsschliff experimentell geprüft. Die Empfindlichkeit dieser Methode für den Nachweis von Bi wird diskutiert und liegt in der Größenordnung der besten bisher bekannten analytischen Methoden. Sie ist in der Größenordnung von 10^–8 gr Bi/gr. Gestein.Mit 4 Textabbildungen.     

Mare basalt units and the compositions of their magmas

A synthesis of the majority of the available mare basalt data shows that basalts and glasses came from 28 different volcanic units. The compositions of the magmas of 12 of these units can be calculated with a high degree of confidence. Reasonable estimates can be made for the compositions of nine of the remaining units. In addition, the compositions of three general magma types can be obtained from data derived from the Luna 16, Luna 24, and Apollo 17 fines. The compositional data presented provide a firm basis for the further study of the characteristics of the mare basalt magma source region.     

Buchbesprechung

Ohne Zusammenfassung     

Radio observations of the radio galaxy 3C 390.3 at 0.6 GHz

Observations of the radio galaxy 3C 390.3 made with the 3-km WSRT at 0.6 GHz are presented. This is an edge-brightened double source with strong bridges connecting the hot spots to the core. Complex linear polarization structure has been detected. The south component is double, the north component, triple. This 3-km observation at 0.6 GHz has been compared with the 1.5-km WSRT observation at 1.4 GHz and some important physical parameters of the sources have been evaluated.     

Interaction of the Large Magellanic Cloud with the halo population and the companions of the Galaxy

Numerical simulations have been performed in order to study the gravitational interaction between the outlying population of the Galaxy and the Large Magellanic Cloud (LMC). The following effects have been noted: (1) halo objects are partially removed from the orbital distance of the LMC such that a local minimum is created in the radial density profile; (2) a large number of halo objects go into escape orbits. This possibility makes the determination of the mass of the Galaxy by virial theorem arguments unreliable; (3) the orbit of the LMC decays faster than what one would expect on the basis of the classical dynamical friction calculation. The excess friction derives from three-body effects, which are not accounted for in the classical dynamical friction. Finally, the fates of globular clusters and dwarf galaxies near the Galaxy and the LMC are discussed.