Beschreibung
The publication in English of this monograph seems to me to indicate the ever increasing interest of astrophysicists in the physical and dynamical problems of planetary nebulae-one of the most interesting and fruitful branches of theoretical astrophysics. Their interest in part arises from the fact that the methods of identify ing the physical processes occurring in planetary nebulae, as well as the many theo retical results, are now acquiring a degree of uni versality as their sphere of application increases. Finally, the special cosmic significance of planetary nebulae is becoming apparent. The English edition of Planetary Nebulae differs considerably from the Russian version published in 1962, primarily because of the new results included in it, but also because of numerous editorial revisions. The problems of magnetic fields and hydrodynamics in planetary nebulae are beginning to occupy an important place in the study of the dynamics of these objects. Recent studies by D. H. Menzel confirm the idea advanced in the present mono graph as to the existence of magnetic fields in planetary nebulae. New light is being cast on the dynamics of planetary nebulae by the hydrodynamic investigations of F. D. Kahn, W. G. Mathews and others. Unfortunately I was not able to include these and other interesting results in the present edition.
Autorenporträt
InhaltsangabeI. Basic Observational Data.- 1. Forms of planetary nebulae.- 2. The structure of nebulae.- 3. Luminosity of nebulae and their nuclei.- 4. The spectra of nebulae.- 5. The spectra of the nuclei.- 6. Stratification of radiation.- 7. Expansion of planetary nebulae.- 8. Apparent distribution of planetary nebulae.- 9. Planetary nebulae in other galaxies.- 10. Spectral and morphological classification of nebulae.- 11. Designations and catalogues.- II. The Origin of Emission Lines.- 1. The nature of nebular emission.- 2. Rosseland's theorem.- 3. Fluorescence-Zanstra's theory.- 4. Excitation of the forbidden lines.- 5. Accumulation of atoms in metastable levels.- 6. The role of electron collisions.- 7. The stratification of radiation.- 8. The intensity of the Balmer lines.- 9. Degree of excitation.- 10. Ionization in the nebula.- 11. Ionization and excitation by electronic collisions.- 12. Chemical composition of planetary nebulae.- 13. Continuous absorption coefficients of several elements.- III. The Problem of Distances and Dimensions of Planetary Nebulae.- 1. The state of the problem.- 2. Methods of determining distances of planetary nebulae.- 3. The dispersion of luminosity and mass in planetary nebulae.- 4. Astrophysical methods of determining the distances of nebulae.- IV. Temperatures of Nuclei, Electron Temperatures and Electron Concentrations.- 1. Methods of determining temperatures of nuclei.- 2. Electron temperatures.- 3. Cooling of the inner regions of nebulae.- 4. The temperature gradients in nebulae.- 5. The possibility of determining the electron temperature of the central regions of nebulae from observations.- 6. The electron concentration.- 7. Planetary nebulae with very high densities.- 8. The masses of planetary nebulae.- V. The Continuous Spectrum of Planetary Nebulae.- 1. Observational data.- 2. Theory of two-quantum emission.- 3. The effects of collisions.- 4. Processes degrading L?-photons.- 5. The intensity of continuous radiation.- 6. Continuous emission of unknown origin.- 7. The possibility of synchrotron radiation.- 8. The possibility of radio emission.- VI. Radiative Equilibrum of Planetary Nebulae.- 1. The Lc-radiation field.- 2. The L?-radiation field.- 3. The radiation field in an expanding nebula.- 4. Diffusion of L?-radiation.- 5. Relaxation time.- 6. Radiation pressure in nebulae.- 7. The expansion of nebulae.- 8. The effect of thermal expansion. "Vacuum" in the centers of nebulae.- 9. Deceleration of nebulae.- VII. Double-Envelope Nebulae.- 1. Observations of double-envelope nebulae.- 2. Basic properties.- 3. The origin of the second envelope.- 4. The evolution of planetary nebulae.- 5. The theory of envelope separation.- 6. On the optical depth.- 7. Ring nebulae.- VIII. The Stability of the Forms of Gaseous Envelopes.- 1. The hydrodynamics of planetary nebulae.- 2. Statement of the problem.- 3. The stability of the forms of gaseous envelopes.- 4. The stability of planetary nebulae.- 5. The stability of nova envelopes.- 6. Stability of the envelopes of Wolf-Rayet stars.- 7. Application of the theory to duffuse nebulae.- 8. The influence of macroturbulence on the stability of the envelopes.- 9. On the motion of planetary nebulae in the interstellar medium.- IX. Magnetic Fields in Planetary Nebulae.- 1. The role of Galactic magnetic fields.- 2. Mechanical equilibrium in planetary nebulae with a magnetic field.- 3. Energy equilibrium of planetary nebulae.- 4. A point dipole.- 5. An extended dipole.- 6. Brightness distribution of a nebula with a magnetic field.- 7. Elongated nebulae.- 8. "Rectangular" nebulae.- 9. The magnetic field of NGC7293.- 10. Spiral planetary nebulae.- 11. Dissipation of magnetic energy.- 12. The interstellar magnetic field of the intermediate Galactic system.- 13. Some conclusions.- X. The Origin of Planetary Nebulae.- 1. The ejection hypothesis.- 2. The "residue" theory.- 3. The early age of the nuclei.- 4. The evolution of nuclei.- 5. The temperature of IC4997.- 6. The contrib
