Nebula diffuse

Evidence of a relation between carbon particles and DIBs can be found in the analysis of the Red Rectangle spectrum. This object is a losing mass carbon star probably evolving to a planetary nebula phase. Diverse spectroscopic studies have revealed the good agreement between the emission lines found at 5,797, 5,850, 6,379, and 6,614 A and some of the most intense diffuse bands of the interstellar medium. It is likely that the carrier of some of these interstellar bands is also present in the material ejected by this object. 

The best evidence for a relation between carbon-particles and the diffuse interstellar bands comes from analysis of the Red Rectangle. The Red Rectangle is an usual mass-losing carbon star which is probably in transition into becoming a planetary nebula. Schmidt et al. (1980) using 6-20 A resolution discovered intense optical emission bands longward of 5400 A. With a higher spectral resolution of 1 A,... 

With current instruments it is possible to make spatial maps of the emission from different species in the Red Rectangle. These maps might provide valuable clues to the origin of different spectroscopic features. For example, in the spectrum of the Red Rectangle, the emission features which correspond to the diffuse interstellar bands are concentrated in what appears to be two hollow cones oriented perpendicular to the plane of this bipolar system (Schmidt Witt 1991). This hollow cone is similar to that proposed by Jura Kroto (1990) to explain the observed (Nguyen-Q-Rieu et al. 1986) HC,N emission (see around AFGL 2688, the Egg Nebula ), a very well studied carbon-rich object that appears to be in transition from a red giant to a planetary nebula. 

V2 Dt, where t is time, and D is the diffusion coefficient) with penetration depth that, except for He and Ne, other noble gas atoms can hardly diffuse out from the target material if the irradiated materials were kept at 0°C for more than 107 years. The latter conditions are likely to approximate those in the preaccretionary solar nebula. Therefore, considering all these experimental results, we may conclude that implantation is unlikely to have played a major role in acquiring noble gases by the Earth. 

Very poetic, Bob says. Earth s astronomers have catalogued over 1,600 planetary nebulas, but we know there were tens of thousands in the Milky Way. They were probably less than 50,000 years old, because the nebula quickly diffuses away. ... 

There is evidence from chondrites that the solar nebula was well mixed between 0.1 and 10 AU during its first several million years of the evolution, as shown by the homogeneity in concentrations of many isotopes of refractory elements (Boss 2004 Chapter 9). This is likely caused by the evaporation and recondensation of solids in the very hot inner nebula, followed by outward transport due to turbulent diffusion and angular momentum removal. Materials out of which terrestrial planets and asteroids are built have been heated to temperatures above 1300 K and are thus depleted in volatile elements. The inner solar nebula, with some exceptions, does not retain memories of the pristine interstellar medium (ISM) chemical composition (Palme 2001 Trieloff Palme 2006). 

In interstellar space, matter is distributed very unevenly. As already mentioned in section 14.4, some stars are ejecting their matter in form of nebulas of dust and gas. These nebulas contain various elements (mainly H, C, O, Si and others) at temperatures between about 10 and 10 K. Far away from the stars, the density of interstellar matter is of the order of 0.1 atom per cm, mainly H and C. In some regions, however, matter is condensed in the form of big interstellar clouds, the mass of which may exceed the mass of the sun by a factor of 10 or more. Two types of interstellar clouds are distinguished optically transparent, diffuse clouds containing <10 atoms per cm (mainly H, but also some compoimds such as CO or HCFIO) at temperatures of the order of 100 K, and opaque, dense clouds containing lO to 10 molecules per cm (mainly H2, but also a variety of compounds) at temperatures varying between about 10 and 10 K. Densities and temperatures increase from the outer parts to the core of the clouds. 

Ozawa K. and Nagahara H. (2000) Kinetics of diffusion-controlled evaporation of Fe-Mg olivine experimental study and implication for stability of Fe-rich olivine in the solar nebula. Geochim. Cosmochim. Acta 64, 939-955. 

Stevenson D. J. and Lunine J. 1. (1988) Rapid formation of Jupiter by diffuse redistribution of water vapor in the Solar Nebula. Icarus 75, 146-155. 

The Milagro detector s large field of view and continuous duty cycle make it an ideal instrument for the discovery of previously unknown sources. Recent publications cover topics including detection of the Crab Nebula[l], limits on TeV emission from GRB [2] and a TeV all-sky survey of the northern celestial hemisphere[3]. Recently we have presented papers on the detection of diffuse TeV emission from the Galactic plane[4], limits on TeV emission from satellite detected GRB[5], a study of nearby AGN[6] and limits on relic neutralino annihilation derived from TeV flux limits from the sun[7]. The focus of this paper is the search for extended sources of TeV gamma rays with the Milagro detector. 

---