Planetary system formation

We refer the interested reader to the paper by Bossi et al., where this problem is discussed in detail in its parallel aspects of star formation and planetary system formation. 

A range of parameters may exist for /, because of computational fiitiactabiUty such as currently afflicts planetary-system formation [15] or even of the lack of a theory about the existence of a unique putative characterization / [4, 5, 6]. Unlike the case for the usable subset N, identified uniquely by the Standard Model and methodological constraints, it makes sense to sum over the parameters of / with some distribution P(x ) The nuclear and astrophysical inputs provide a joint distribution ... 

Sozzetti MT, Lattanzi MG, Boss AP (eds) (2011) The astrophysics of planetary systems formation, structure, and dynamical evolution. Proceedings lAU symposium, 276 Torino... 

Nucleosynthesis in AGB stars and its relevance for galactic enrichment and planetary system formation was reviewed by Busso, Gallino, and Wasserburg, 1999 [52]. They stressed the importance of neutron capture by a process like C(o , n) 0. This means that a carbon isotope reacts with an a particle and the result is an oxygen plus a neutron, n. 

R = the average rate of star formation in our galaxy fs = the fraction of stars that are suitable suns for planetary systems fp = the fraction of suitable suns with planetary systems ne = the mean number of planets that are capable of supporting life fi = the fraction of such planets on which life actually originates fi = the fraction of such planets on which some form of intelligence arises fc = the fraction of such intelligent species that develop the ability and desire to communicate with other civilizations L = the mean lifetime (in years) of a communicative civilization... 

The discovery of the average metal-rich nature of planet-harbouring stars with regard to disc stars (i.e. [1],[2], [3]) has revealed the key role that metallicity plays in the formation and evolution of planetary systems. If the accretion processes were the main responsible for the iron excess found in planet host stars, volatile abundances should show clear differences in stars with and without planets, since volatiles (with low Tc) are expected to be deficient in accreted materials [4]. Previous studies of the abundance trends of the volatiles N, C, S and Zn [5, 6] have obtained no anomalies for a large sample of planet host stars. 

As a concluding remark of this section, the theoretical models of nucleosynthesis within stars show that the isotopic compositions of the elements are highly variable depending on star size, metallicity, companion s presence. From the isotopic data obtained in diverse solar system materials it turns out that most of this material was highly homogenized in the interstellar medium or by the formation of the solar system. The presence of isotopic anomalies preserved in some primitive materials are the last witnesses of the initial diversity of the materials constituting our planetary system. 

That s the only way to get a lot of carbon out of the star and into space. But supernovas can t be too common or else they would destroy too many worlds. On the other hand, as I mentioned before, supernovas are important because the shock waves they produce can cause planetary systems to start to coalesce from dust clouds surrounding other stars. This means that there can t be too many supernovas or too few. Any substantial deviation would decrease planetary formation and the emergence of life. ... 

Allamandola and Hudgins have considered the formation of complex organic species in ice matrices and provided a summary of the photochemical evolution on those ices found in the densest regions of molecular clouds, the regions where stars and planetary systems are formed 42 Ultraviolet photolysis of these ices produces many new compounds, some of which have prebiotic possibilities. These compounds might have played a part in organic chemistry on early Earth. 

Abstract Planet formation is a very complex process through which initially submicron-sized dust grains evolve into rocky, icy, and giant planets. The physical growth is accompanied by chemical, isotopic, and thermal evolution of the disk material, processes important to understanding how the initial conditions determine the properties of the forming planetary systems. Here we review the principal stages of planet formation and briefly introduce key concepts and evidence types available to constrain these. 

Transient heating events were important in the formation of the Solar System and provided the energy to produce chondrules and refractory inclusions. These objects are not predicted in astrophysical models for the formation of planetary systems. They comprise 50-80% of the mass of many primitive meteorites. However, the mechanism that produced the transient heating events is still unknown. Future work must focus on putting the details of the petrographic and chemical analysis of these rocks into an astrophysical and cosmochemical framework of Solar System formation. 

Since jqZq seems to set the lower limit for efficient dust formation,4 planetary systems are only expected to form around stars with at least this metallicity. The relative abundances of rock-forming elements in such systems are essentially the same as in the Solar System. Only the total amount of such elements may vary considerably, depending on the birthplace and birth-time of such systems. Planetary systems with unusual elemental compositions, e.g. like those observed in many highly evolved stars, are not expected to exist in particular, oxygen is always more abundant than carbon such that for planetary systems there is no counterpart to the carbon-rich circumstellar dust shells. 

Planetary systems are now generally believed to be by-products of the process of star formation. Star formation, therefore, is the natural starting point for discussions of planet formation. Almost all stars are born as members of stellar clusters that, in turn, are bom in molecular clouds. Formation of isolated stars seems to be possible according to observations, but this is a rare process. Whether the Sun and its associated planetary system formed in isolation or as member of a cluster is not known some indications hint to formation in a cluster (see Hester Desch 2005 Gounelle Meibom 2008 and Chapter 9, this volume). 

There is convincing observational evidence that the placental interstellar medium (ISM) from which the solar system originated was a dense molecular cloud (Wasserburg et al., 1982 1979). In fact, the recent evidence of the presence of short-lived nuclei in meteorites requires that the free-fall time scale for gravitational collapse (tft) be less than or comparable to the mean lifetime of Al ( 10 yrs), i.e. ttt 4.10 / /n < 10 yrs, which requires nn lOVcc, a value typical of molecular clouds. Since molecular clouds are observed to be a major feature in our galaxy, they constitute a most reliable starting point for the processes that will eventually lead to the formation of stars and planetary systems (Falk and... 

In this chapter, we focus on the insights that chondrites offer into the earliest stages in the formation of asteroids and planetesimals in the solar nebula— the protoplanetary disk of dust and gas that evolved into the planetary system. Other chapters review many other aspects of chondrite studies. 

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