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Book Physics of Thermal Gaseous Nebulae

Download or read book Physics of Thermal Gaseous Nebulae written by L.H. Aller and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gaseous nebulae offer outstanding opportunities to atomic physicists, spectroscopists, plasma experts, and to observers and theoreticians alike for the study of attenuated ionized gases. These nebulae are often dusty, heated by radiation fields and by shocks. They are short-lived phenomena on the scale of a stellar lifetime, but their chemical compositions and internal kinematics may give important clues to advanced stages of stellar evolution. The material herein presented is based on lectures given at the University of Michigan, University of Queensland, University of California, Los Angeles, and in more abbreviated form at the Raman Institute, at the Scuola Internazionale di Trieste, and elsewhere. Much of it is derived origionally from the series "Physical Processes in Gaseous Nebulae" initiated at the Harvard College Observatory in the late 1930s. I have tried to emphasize the basic physics of the mechanisms involved and mention some of the uncertainties that underlie calculations of many basic parameters. Emphasis is placed on ionized plasmas with electron temperatures typically in the neighborhood of 10,OOOoK. Dust and other ingredients of the cold component of the interstellar medium are treated briefly from the point of view of their relation to hot plasmas of H II regions and planetaries. Chemical composition determinations for nebulae are discussed in some detail while the last section deals with interpretations of elemental abundances in the framework of stellar evolution and nucleogenesis. Gaseous nebulae offer some particularly engaging opportunities for studies of stellar evolution.

Book Astrophysics Of Gas Nebulae and Active Galactic Nuclei

Download or read book Astrophysics Of Gas Nebulae and Active Galactic Nuclei written by Donald E. Osterbrock and published by University Science Books. This book was released on 2006 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thoroughly revised and expanded throughout, the new edition is a graduate-level text and reference book on gaseous nebulae, nova and supernova remnants. Much of the new data and new images are from the Hubble Space Telescope with two wholly new chapters being added along with other new features. The previous edition which was tried and tested for thirty years has now been succeeded by a revised, updated, larger edition, which will be valuable to anyone seriously interested in astrophysics.

Book Ionized Gaseous Nebulae

Download or read book Ionized Gaseous Nebulae written by William J. Henney and published by . This book was released on 2002 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Ionization Structure in Gaseous Nebulae

Download or read book Ionization Structure in Gaseous Nebulae written by David Julian Pace and published by . This book was released on 1974 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Selected Papers on Physical Processes in Ionized Plasmas

Download or read book Selected Papers on Physical Processes in Ionized Plasmas written by Donald Howard Menzel and published by . This book was released on 1962 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contains contributed articles to the history of the 1848 revolutions ; intends to interpret historical truth for the "people" whom the historians exemplified were the real victors of 1848.

Book The Physics and Dynamics of Planetary Nebulae

Download or read book The Physics and Dynamics of Planetary Nebulae written by Grigor A. Gurzadyan and published by Springer Science & Business Media. This book was released on 2013-04-09 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt: Planetary nebulae are the classic subject of astrophysics. The physical pro cesses occurring in this highly ionized gaseous medium, the formation of emis sion lines in clearly specified conditions, the continuous emission extending from the far ultraviolet up to infrared and radio frequencies, the generation of exotic forms of radiation predicted by atomic physics, along with methods for deciphering the observed spectra and detecting physical and kinematic parameters of the radiating medium, etc. - all these problems form the solid foundations of the physical theory of gaseous nebulae. They are an essential part of the arsenal of powerful tools and concepts without which one cannot imagine understanding and interpreting the enormous diversity of processes taking place in the Universe - in gaseous envelopes surrounding the stars of various classes, from cool dwarfs and flare stars up to hot supergiants, as well as in stellar chromospheres and coronae, in atmospheres of unstable and anomalous stars, in circumstellar clouds and gaseous shells born in nova and supernova explosions, in diffuse nebulae and the interstellar medium, in interacting binary systems, in galaxies with emission lines, in quasars, etc. The last thirty years have seen a turning-point in our knowledge concern ing the very nature of planetary nebulae (PNs). The radio emission of PNs was discovered after it was predicted theoretically. On the other hand, the powerful infrared emission discovered both in the continuum and in emission lines was never expected.

Book Time dependent Photoionization of Gaseous Nebulae

Download or read book Time dependent Photoionization of Gaseous Nebulae written by Ehab Elsayed Elhoussieny Ahmed and published by . This book was released on 2017 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: We study time-dependent photoionization of gaseous nebulae, i.e. the physical conditions and spectra of astronomical plasmas photoionized by a time-dependent source of ionizing radiation. Our study proceeds in two chief steps: First, we start with a simplified model of plasmas of pure H. Second, we develop a more realistic model of plasmas composed of a mixture of chemical elements. For the first step, we wrote a time-dependent photoionization code (TDP) that solves the coupled system of equations for ionization, energy balance, and radiation transfer in their full time-dependent forms For the second step, we developed a more realistic code (TDXSTAR) to solve for the excitation, ionization, thermal, and radiative transfer equations in their full time-dependent forms using full atomic model. The TDXSTAR code is based on the well known steady-state code XSTAR and capable of including all chemical elements from hydrogen (Z=1) to nickel (Z=28). TDP and TDXSTAR simulations of a pure hydrogen nebula with constant density show that ionization and thermal fronts are created due to flux variations and propagate (often supersonic) through the cloud over time scales that vary widely and non-linearly across the nebula. Further, simulations for slabs initially in pressure equilibrium show that thermal and pressure fronts propagate through the plasma, which become particularly pronounced across the ionization front (IF). In addition, periodic variations in the ionizing flux lead to the following conclusions, (1) the instantaneous physical conditions of the plasma are different from any steady-state solution, (2) the time-averaged conditions are different from any steady-state solution and characterized by over-ionization and a broader IF with respect to the steady-state solution for a mean value of the radiation flux. (3) the dispersions in the physical conditions from their time-averaged values are increase period of variations in the flux, (4) variations in physical conditions are asynchronous along the slab due to the combination of non-linear propagation times for thermal and ionization fronts and equilibration times. Further, we used TDXSTAR to study the physical conditions in planetary nebulae (PNe) that are experiencing a steady decline in stellar temperature. Simulations show that spectra of different ions respond differently to the stellar evolution; while some lines decay others are enhanced. Differences in initial stellar temperatures don't affect the spectral lines trend. However, higher initial stellar temperature yield more intense forbidden lines due to the higher electron temperature. Moreover, models with different gas densities show that gas densities determine the time scale of the gas response to the changes in the ionizing radiation. Furthermore, models of different fixed luminosities produce similar conditions throughout the nebulae where luminosities and distances scale in a way such that the radiation field stays nearly the same across the nebulae, with the exception He II lines. In addition, we studied the time-dependent effects in H II regions and planetary nebulae ionized by binary systems. Simulations of different periods from a few days to decades show that short-period binaries (with periods much shorter than equilibration times in the gas) have no noticeable effects on the gas conditions. In contrast, binary systems with long periods (comparable to equilibration times in the nebula) have noticeable effects on gas conditions. The time-averaged temperature profiles are different from the steady-states corresponding to the mean flux. Further, time-averaged temperature profiles show two peaks and flatter profiles compared to that of the steady-state corresponding to the mean of the ionizing flux. The two-peak average temperature profiles suggest binaries as probable sources of temperature fluctuations. Furthermore, the average temperature weighted by collisionally excited and recombination lines integrated over nebular volume exhibit clear discrepancies in the temperature. Thus, adopting an average temperature for spectroscopic abundances determinations are expected to lead to discordances in the estimated abundances.

Book Gaseous Nebulae

    Book Details:
  • Author : Lawrence Hugh Aller
  • Publisher :
  • Release : 1956
  • ISBN :
  • Pages : 378 pages

Download or read book Gaseous Nebulae written by Lawrence Hugh Aller and published by . This book was released on 1956 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Physical Processes in Gaseous Nebulae

Download or read book Physical Processes in Gaseous Nebulae written by Donald Howard Menzel and published by . This book was released on 1937 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Charged Particle Induced Heating of a Gaseous Nebula

Download or read book Charged Particle Induced Heating of a Gaseous Nebula written by Gerald T. Davidson and published by . This book was released on 1963 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Ionization Correction Factors for Low excitation Gaseous Nebulae

Download or read book Ionization Correction Factors for Low excitation Gaseous Nebulae written by John S. Mathis and published by . This book was released on 1984 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Spectroscopy for Amateur Astronomers

Download or read book Spectroscopy for Amateur Astronomers written by Marc F. M. Trypsteen and published by Cambridge University Press. This book was released on 2017-07-20 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: This accessible guide presents the astrophysical concepts behind astronomical spectroscopy, covering both theoretical and practical elements. Suitable for anyone with only a little background knowledge and access to amateur-level equipment, it will help you understand and practise the scientifically important and growing field of amateur astronomy.

Book Gaseous Nebulae and the Interstellar Medium  notes  Graduate Course  University of Michigan  1st Semester 1960 61

Download or read book Gaseous Nebulae and the Interstellar Medium notes Graduate Course University of Michigan 1st Semester 1960 61 written by Herman Zanstra and published by . This book was released on 1963 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Ionized gaseous nebulae

    Book Details:
  • Author : William J. Henney
  • Publisher :
  • Release : 2002
  • ISBN :
  • Pages : 290 pages

Download or read book Ionized gaseous nebulae written by William J. Henney and published by . This book was released on 2002 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Some Calculations of Cooling Rates and Spectral Emission of Gaseous Nebulae

Download or read book Some Calculations of Cooling Rates and Spectral Emission of Gaseous Nebulae written by Donald Peyton Cox and published by . This book was released on 1970 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Ionization in Nebular Matter

Download or read book Ionization in Nebular Matter written by B. P. Gerasimovič and published by . This book was released on 1927 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: