Clouds planetary systems

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. 

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... 

Interstellar clouds, tlie birthplace of stars and planetary systems, are rich in simple organic materials and radicals in tlie gas phase and may contain more complex molecules and even macromolecular organic matter on grains. Although these complicated molecules have not been observed in interstellar... 

Kaiser, R.I. Balucani, N. Asvany, O. Lee, Y.T. Crossed molecular beam experiments of radical-neutral reactions relevant to the formation of hydrogen deficient molecules in extraterrestrial environments. In Astrochemistry from Molecular Clouds to Planetary Systems. Mihn, Y.C., van Dishoek, E.F., Eds., Astronomical Society of the Pacific - lAU Series, Volume 197, 2000, 251-264. 

The Universe was already 9 billion years old when our solar system was born at 4.567 Ga. The compression and collapse of a gas cloud in the interstellar medium gave rise to a flattened disk of gas and dust rotating around an otherwise nondescript, medium-sized star. It was in this rotating disk of gas and dust - the primitive solar nebula - that our planetary system was formed. 

It is within cold, dark molecular clouds such as this that new stars and planetary systems are bom (Plate 1). Once part of a molecular cloud becomes unstable under its own gravitational field, it will begin to collapse, forming a protostar. As this collapse proceeds, the angular momentum possessed by the infalling material draws it into a disk. Planetary systems are thought to coalesce... 

This activity is in an area of the first stirrings of interest in astrobiology, since the molecular clouds in the ISM contain the raw material for the formation of stars and their planetary systems and the subsequent development of life, at least oti our Earth and possibly elsewhere. Cosmochemical models, which include a number of... 

Ear from being just the processing of water on Earth, this cycle is the basis for a wide range of meteorologic, geochemical, and biological systems. Water is the transport medium for all nutrients in the biosphere. Water vapor condensed into clouds is the chief control on planetary albedo. The cycling of water is also one of the major mechanisms for the transportation of sensible heat (e.g. in oceanic circulation) and latent heat that is released when water falls from the air. 

Clouds. Cloud feedback mechanisms are among the most complex in the climate system, due to the many disparate roles played by clouds, which control a large portion of the planetary albedo but also trap terrestrial radiation, reducing the energy escaping to space. To complicate matters further, different t5 es of clouds behave differently in the same environment. In the present climate mode, clouds have... 

---