Detection of a strongly negative surface potential at Saturn's moon Hyperion

On 26 September 2005, Cassini conducted its only close targeted flyby of Saturn's small, irregularly shaped moon Hyperion. Approximately 6 min before the closest approach, the electron spectrometer (ELS), part of the Cassini Plasma Spectrometer (CAPS) detected a field-aligned electron population originating from the direction of the moon's surface. Plasma wave activity detected by the Radio and Plasma Wave instrument suggests electron beam activity. A dropout in energetic electrons was observed by both CAPS-ELS and the Magnetospheric Imaging Instrument Low-Energy Magnetospheric Measurement System, indicating that the moon and the spacecraft were magnetically connected when the field-aligned electron population was observed. We show that this constitutes a remote detection of a strongly negative (~ −200 V) surface potential on Hyperion, consistent with the predicted surface potential in regions near the solar terminator

The angular momentum-vs-mass relation and the distribution of mass ratios for visual binary systems

The investigation of the angular momentum vs mass relation for binary stars is completed with a study of the 847 systems contained in the Fourth Catalog of Orbits of Visual Binary Stars. Because both J and M of a visual binary depend steeply on the distance to the system (5th and 3rd powers, respectively), and many of the distances are not well known, the study makes use of an auxiliary parameter R which is independent of distance and proportional to JM-5/3. R appears to be uncorrelated with M for the 789 systems for which both can be determined. The non-correlation implies that J ∝M5/3, expected from Kepler's third law, provides a better fit to the visual binaries than does J ∝M2, predicted by some more complex considerations. The distribution function f(q=M2/M1) of mass ratios for the visual binaries results as a byproduct of the investigation. It peaks extremely sharply toward q=1.0 (much more so than for spectroscopic binaries). Because most visual binaries are wide enough to consist of stars that condensed independently (and so that can be thought of as chosen at random from an initial mass function), one expects the real f(q) to rise toward low ratios. Observational selection against the discovery and study of systems with large magnitude differences between the components must be very large indeed to account for the discrepancy between expectation and observation. The alternative is a mechanism for formation of wide binaries that favours equal components. The distribution of mass ratios for eclipsing binaries is given in an appendix. It peaks strongly at q=0.6-0.75 and largely reflects processes of angular momentum, mass, and energy exchange between the stars in contact systems. © 1986 D. Reidel Publishing Company

MOLECULAR SPECTROSCOPY OF NUCLEAR PARTICLES

Author Institution: Westinghouse Research Laboratories, Pittsburgh 35The discovery of a rapidly growing number of short-lived, excited systems among high-energy nuclear particles suggests the possibility of an underlying molecular type of structure for these particles to which the concepts of molecular spectroscopy appear to be applicable. It is found that the observed spin and masses of the heavy mesons and ``resonance'' particles can be accounted for in terms of the rotational excited states of ``pionic-molecules'' consisting of 2, 3, 4, and $5 \pi$-mesons. The bond-length and binding energy per bond can be obtained from a relativistic electron-positron model of the $\pi$-mesons which is also able to account for the observed masses, spins, and life-times of the $\pi$-mesons themselves. Such a molecular structure of nuclear particles permits one to obtain a physical interpretation of the ``isotopic spin'' and ``strangeness'' quantum numbers introduced for empirical reasons in terms of the internal structure and angular momenta of these systems. Furthermore, it provides an explanation for the usefulness of group-theoretical symmetry arguments which have recently been widely applied to the classification of the newly discovered particles. The desirability of applying the powerful techniques developed for the analysis of molecular spectra to the problem of nuclear particle structure is suggested