The search for intelligent life or any type of life involves processes with nonlinear chaotic behaviours throughout the Universe. Through the sensitive dependence condition, chaotic dynamics are also difficult or impossible to duplicate, forecast and predict. Similar evolution patterns will result in completely different outcomes. Even, the intelligent life evolution pattern, based on carbon, DNA–RNA–protein, will differ from all possible sequences. In the present paper, the stochastic dyadic Cantor set models the many possible variations of such chaotic behaviours in the Universe, yielding to a tendency to zero, for any scenario of intelligent life evolution. The probability of the development of the exact microscopic and macroscopic scenario that is capable of supporting intelligent life or any other type of life in any planet is vanishingly small. Thus, the present analysis suggests that mankind, as an extremely statistically uncommon occurrence, is unique and alone in the Universe.

Using a collection of 40 debris disks (DD) around dwarf A-type stars (from which 17 are spatially resolved) having well determined stellar ages (Vican 2012), we found that for a collisional self-stirring model of flux distributions (Kenyon & Bromley, 2008, 2010) dusty DD occupy for a large part the terminal age positions corresponding the end of the MS phase. This situation does not necessarily mean that the dust generation in these DD is finished at this stage. Dusty DD can continue their lives in the next Post-MS stages, as is the case of the recent first resolved dusty DD with planets around the K-type subgiant star κ CrB. This star is considered a “retired” A star (Bonsor et al. 2013). In order to explain the apparent lack of dusty DD in the giant phase, we propose here that this could be due, in part, to a dilution of any planetesimal belt existing around these stars, with the corresponding diminishing of collisions and subsequent dust generation. This dilution is provoked by the dynamical expansion of this belt produced by the important stellar mass loss during the RGB phase. This scenario is being studied by means of numerical simulations by de la Reza, Roig & Chavero 2013 (in preparation).

We numerically investigate the conditions for planetesimal accretion in the circumprimary disk under the perturbing presence of a companion star, with focus on the γ Cephei system. Gas drag is included with a dissipating time scale of 105 years. We show at the beginning(within 103 ∼ 104 years), gas drag damps the ΔV between planetesimals of same sizes and increases ΔV between planetesimals of different sizes. However, after increasing to high values(300∼800m/s), we find the ΔV between bodies of different sizes decrease to very low values (below 10m/s) in a few 105yrs (depending on the gas-dissipating time scale Tdamp, radial size Rp and semi-major axis ap of planetesimals). Hence, the high ΔV is somewhat short-lived, and runaway accretion can be turned on later. We conclude that the conditions for planetary formation in binary systems (even close binary systems) are much better than what we expected before.

Some circumstantial evidence for residual planetesimals is constructed based on the recent discovery of a dusty ring around a young white dwarf at the center of the Helix nebula (Su et al. 2007). This ring extends between about 35 and 150 AU from the nebula center, and have a total mass of about 0.13 M⊕. In this paper we propose that this ring is the by-product of planets and planetesimals' orbital evolution during the epoch when the central star rapidly lost most of its mass. We examine the dynamical evolution of planetary systems similar to the solar system (i.e. with gas giant planets and residual planetesimals) as their host stars evolve off the main sequence. During the process, some planetesimals will be captured by the gas giants into mean motion resonances and their mutual collisions will form a dust ring similar to that observed at the center of the Helix nebula.

The early gas and dust protosolar nebula of the solar composition is considered analytically. A simultaneous formation of the sun and all the planets around it ($\approx 5 \times 10^9$ yr ago) through a local gravitational Jeans-type instability of small-amplitude gravity perturbations in the nebula disk is suggested. It is shown that a collective process, forming the basis of the disk instability hypothesis, solves with surprising simplicity the two main problems of the dynamical characteristics of the system, which are associated with its observed spacing and orbital momentum distribution, namely, Bode's law on planet spacing and the concentration of angular momentum in the planets and mass in the sun. Besides, the analysis is found to imply the existence of new planets or other Kuiper-type belts of comets at mean distances from the sun of 87 AU, 151 AU, 261 AU, 452 AU, 781 AU (Mercury, Venus, $\ldots$, Asteroid belt, $\ldots$, Neptune, Kuiper belt, new planets or other Kuiper-type belts).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html