Saturn: Origin and composition of its inner moons and rings

The contraction of the primitive protosaturnian cloud, using ideas of supersonic turbulent convection was modeled. The model suggested that each of Saturn's inner moons, excepting Rhea, condensed above the ice-point of water and consists primarily of hydrous magnesium silicates. The satellite mean densities steadily increase towards the planet and the rocky moons are irregular in shape

Voyager and the origin of the solar system

A unified model for the formation of regular satellite systems and the planetary system is outlined. The basis for this modern Laplacian theory is that there existed a large supersonic turbulent stress arising from overshooting convective motions within the three primitive gaseous clouds which formed Jupiter, Saturn, and the Sun. Calculations show that if each cloud possessed the same fraction of supersonic turbulent energy, equal to about 5% of the cloud's gravitational potential energy, then the broad mass distribution and chemistry of all regular satellite and planetary systems can be simultaneously accounted for. Titan is probably a captured moon of Saturn. Several predictions about observations made by Voyager 2 at Saturn are presented

Neptune's Triton: A moon rich in dry ice and carbon

The encounter of the spacecraft Voyager 2 with Neptune and its large satellite Triton in August 1989 will provide a crucial test of ideas regarding the origin and chemical composition of the outer solar system. In this pre-encounter publication, the possibility is quantified that Titron is a captured moon which, like Pluto and Charon, originally condensed as a major planetesimal within the gas ring that was shed by the contracting protosolar cloud at Neptune's orbit. Ideas of supersonic convective turbulence are used to compute the gas pressure, temperature and rat of catalytic synthesis of CH4, CO2, and C(s) within the protosolar cloud, assuming that all C is initially present as CO. The calculations lead to a unique composition for Triton, Pluto, Charon: each body consists of, by mass, 18 1/2 percent solid CO2 ice, 4 percent graphite, 1/2 percent CH4 ice, 29 percent methanated water ice and 48 percent of anhydrous rock. This mix has a density consistent with that of the Pluto-Charon system and yields a predicted mean density for Triton of 2.20 + or - 0.5 g/cu cm, for satellite radius equal to 1,750 km

An analysis of the acoustic cavitation noise spectrum: The role of periodic shock waves

Research on applications of acoustic cavitation is often reported in terms of the features within the spectrum of the emissions gathered during cavitation occurrence. There is, however, limited understanding as to the contribution of specific bubble activity to spectral features, beyond a binary interpretation of stable versus inertial cavitation. In this work, laser-nucleation is used to initiate cavitation within a few millimeters of the tip of a needle hydrophone, calibrated for magnitude and phase from 125 kHz to 20 MHz. The bubble activity, acoustically driven at f0 = 692 kHz, is resolved with high-speed shadowgraphic imaging at 5 × 106 frames per second. A synthetic spectrum is constructed from component signals based on the hydrophone data, deconvolved within the calibration bandwidth, in the time domain. Cross correlation coefficients between the experimental and synthetic spectra of 0.97 for the f 0/2 and f 0/3 regimes indicate that periodic shock waves and scattered driving field predominantly account for all spectral features, including the sub-harmonics and their over-harmonics, and harmonics of f 0

The distance to the Vela pulsar gauged with HST parallax oservations

The distance to the Vela pulsar (PSR B0833-45) has been traditionally assumed to be 500 pc. Although affected by a significant uncertainty, this value stuck to both the pulsar and the SNR. In an effort to obtain a model free distance measurement, we have applied high resolution astrometry to the pulsar V~23.6 optical counterpart. Using a set of five HST/WFPC2 observations, we have obtained the first optical measurement of the annual parallax of the Vela pulsar. The parallax turns out to be 3.4 +/- 0.7 mas, implying a distance of 294(-50;+76) pc, i.e. a value significantly lower than previously believed. This affects the estimate of the pulsar absolute luminosity and of its emission efficiency at various wavelengths and confirms the exceptionally high value of the N_e towards the Vela pulsar. Finally, the complete parallax data base allows for a better measurement of the Vela pulsar proper motion (mu_alpha(cos(delta))=-37.2 +/- 1.2 mas/yr; mu_delta=28.2 +/- 1.3 mas/yr after correcting for the peculiar motion of the Sun) which, at the parallax distance, implies a transverse velocity of ~65 km/s. Moreover, the proper motion position angle appears specially well aligned with the axis of symmetry of the X-ray nebula as seen by Chandra. Such an alignment allows to assess the space velocity of the Vela pulsar to be ~81 km/s.Comment: LaTeX, 21 pages, 5 figures. Accepted for publication in Ap