1,720,989 research outputs found
Planet formation process as a phase transition. III - Mass distribution in the outer solar system
No full textOn the basis of the phase transition model for planetary formation, an evaluation is made of the mass which should be present in the part of the solar nebula corresponding to the outer planets. Results confirm the hypothesis of a relevant depletion of the light gas component. This effect increases with the distance from the Sun, lowering the masses of Uranus and Neptune with respect to Saturn and Jupiter: calculations suggest that the original mass in Uranus' and Neptune's zones was almost the same as in that of Saturn
Planet formation process as a phase transition. II - Isoentropic model and comparison with the solar system
No full textWe discuss an adiabatic phase transition between a nebular ring and a protoplanet, taking into account the gravitational corrections to the perfect gas entropy. We compare the results of this model with those found in a previous paper from different assumptions, and we try a qualitative comparison with the structure of the real solar system, using the data for the four giant planets. We discuss the relevance of some primordial phenomena in the formation process of these planets such as a mass depletion within the asteroidal belt, a mass loss from the external regions of the nebula and a decrease of Neptune's orbital radius due to ejection of cometary material. The first and the second process seem to be significantly supported by the results of the phase transition model
FORMATION OF BINARY-SYSTEMS AND PROTOPLANETARY DISKS - A UNIFIED APPROACH
No full textA thermodynamic approach to the last stages of star formation when a collapsing fragment evolves adiabatically into a single protostar is presented. Angular momentum transfer is shown to be a very efficient mechanism tending to form double stars with small mass secondaries, and total decoupling is shown to form twin binaries. It is noted that disks of larger mass, which would be required to produce protoplanetary systems as a consequence of dynamical instabilities, do not form under any circumstances
An explanation for the light curve of Jupiter's and Saturn's satellites
No full textSeveral satellites of Jupiter and Saturn show an asymmetric reflectance between the 'leading' hemisphere (which is generally brighter for the inner satellites of both systems) and the 'trailing' one (which is brighter for the outer satellites Callisto and Iapetus). In order to seek a unified explanation of these observational data it was assumed that, during the final phase of the satellite accumulation process, the surfaces were subjected to a heavy meteoroidal bombardment by the residual bodies in the circumplanetary protosatellite swarms. With suitable hypotheses about the orbital elements of these bodies, the resulting collision rate is anisotropic in an opposite way for inner and outer satellites, with a difference between the two hemispheres of the order of 10-20 percent for all satellites except Iapetus (for which the anisotropy is larger). It is concluded that the model can qualitatively account for the observed effect, even if it is diffcult to propose a detailed mechanism for changing the albedo properties of the satellite surfaces by means of meteoroidal collisions
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