Spectroscopy stellar evolution

Cosmic Radiation Galactic Structure and Evolution Infrared Spectroscopy Interstellar Matter Planetary Satellites, Natural Solar System, General Stellar Spectroscopy Stellar Structure and Evolution Ultraviolet Space Astronomy... 

Atomic Spectrometry Aurora Galactic Structure and Evolution INERARED ASTRONOMY INTERSTELLAR MATTER Planetary Atmospheres Solar Physics Stellar Spectroscopy Stellar Structure AND Evolution telescopes. Optical... 

For purposes of comparison with stellar abundances, it is useful to have the relative contributions of s- and r-processes to the various elements (as opposed to nuclides) in the Solar System, because in most cases only element abundances without isotopic ratios are available from stellar spectroscopy. At the same time, elements formed in one process may often be expected to vary by similar factors in the course of stellar and Galactic evolution, but to be found in differing ratios to elements formed in another process. Relative contributions are listed for some key elements in Table 6.3. 

Stellar spectroscopy has been a very valuable tool for studying the composition and evolution of stars in our Galaxy. Recent improvements in instrumentation and the construction of 8-10m telescopes has allowed this kind of work to be extended to other galaxies. It is not possible yet to do routine spectroscopy of F and G main sequence stars outside the Milky Way, so these studies have concentrated on A and B type supergiants or red giants. Nevertheless, detailed abundance studies of individual stars is not likely to extend far beyond the Local Group for some time because of telescope size limitations. 

Dense molecular clouds, after further contraction, are the places where stars are born. The observation of protostars, stars still embedded in their placental cloud, is a probe of the presence of ices in the clouds the almost black-body continuum emitted from the young object is absorbed by grains whose temperature changes as a function of the distance from the object. These observations, which are mainly obtained by IR spectroscopy, may reveal the evolution of ices due to thermal and/or energetic (e.g. interaction with UV photons and/or stellar particle winds and cosmic rays) processing (e.g. Cox and Kessler [6]). 

Spectroscopy is the key to unlocking the information in starlight. Stellar spectra show a variety of absorption lines which allow a rapid classification of stars in a spectral sequence. This sequence reflects the variations in physical conditions (density, temperature, pressure, size, luminosity) between different stars. The strength of stellar absorption lines relative to the continuum can also be used in a simple way to determine the abundances of the elements in the stellar photosphere and thereby to probe the chemical evolution of the galaxy. Further, the precise wavelength position of spectral lines is a measure of the dynamics of stars and this has been used in recent years to establish the presence of a massive black hole in the centre of our galaxy and the presence of planets around other stars than the Sun. 

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