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Results for “GALACTIC EVOLUTION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1965

Origin of the solar system.

Origin of solar system, discussing monistic and dualistic theory, interstellar gas characteristics, star formation and planetary development

PLANETARY ORIGIN↗
NASA NTRS1966

Astronomical ultraviolet radiation.

Astronomical UV radiation noting galactic composition and extragalactic systems, stellar emission and molecular and atomic H

ULTRAVIOLET RADIATION↗
NASA NTRS1983

X-rays from radio pulsars - The portable supernova remnants

Neutron stars are the longest-lived remnants of supernova explosions. As a reservoir of thermal energy remaining from the explosion and generated by frictional coupling between core and crust, as a storehouse of magnetic and rotational kinetic energy which allows the star to act as a high energy particle accelerator, and as the source of a deep gravitational potential which can generate heat from infalling matter, neutron stars remain capable of producing high energy radiation for a Hubble time. The results of an extensive survey of supernova remnants and radio pulsars performed with the imaging instruments on board the Einstein Observatory are reviewed and the implications of these results for pulsar physics and for the origin and evolution of galactic neutron stars are discussed.

Helfand, D. J.↗
NASA NTRS1985

CNO isotopes in red giant stars

The production and distribution of the CNO nuclides is discussed in light of observed abundance ratios in red giants and in the interstellar medium. Isotope abundances have been measured in the atmospheres and in the recent ejecta of cool giants, including carbon stars, S-type stars and red supergiants as well as in oxygen-rich giants making their first ascent of the giant branch. Several of the observations suggest revision of currently accepted nuclear cross-sections and of the mixing processes operating in giant envelopes. By comparing red giant abundances with high-quality observations of the interstellar medium, conclusions are reached about the contribution of intermediate-mass stars to galactic nuclear evolution. The three oxygen isotopes, O-16, -17 and -18, are particularly valuable for such comparison because they reflect three different stages of stellar nucleosynthesis. One remarkable result comes from observations of O-17/O-18 in several classes of red giant stars. The observed range of values for red giants excludes the entire range of values seen in interstellar molecular clouds. Furthermore, both the observations of stars and interstellar clouds exclude the isotopic ratio found in the solar system.

Wannier, P. G.↗
NASA NTRS1985

CNO isotopes in red giant stars

Observational data on CNO abundance ratios in red giants and the interstellar medium (ISM) are analyzed for the implications for the production and distribution of CNO nuclides. The data included isotope abundance measurements for the atmospheres and recent ejecta of cool giants, e.g., carbon stars, S-type stars, red supergiants and oxygen-rich giants beginning an ascent of the giant branch. The contribution of intermediate-mass stars to galactic nuclear evolution is discussed after comparing red giant abundances with ISM abundances, particularly the isotopes O-16, -17 and -18. The O-12/O-18 ratios of red giants are distinctly different from those in interstellar molecular clouds. The CNO values also vary widely from the values found in the solar system.

Wannier, P. G.↗
NASA NTRS1986

Stellar populations; Proceedings of the Meeting, Baltimore, MD, May 20-22, 1986

Various papers covering recent findings on stellar populations are presented. The topics addressed include: the bulges of the Galaxy and M31, kinematics of the local subdwarfs and the collapse of the Galaxy, the red stellar population of the local group dwarf galaxies, globular clusters in the local group galaxies, the initial mass function, and star formation histories of galactic disks. Also discussed are: yield and abundance constraints on galactic chemical evolution, population synthesis in early type galaxies, the evolution of stellar populations in galaxies, a theoretical perspective on spectral evolution of galaxies, and the structure and kinematics of galaxy populations.

Norman, Colin A.↗