Every 5 years since 1967 a meeting has been held to discuss the subject of planetary nebulae and their central stars. Previous meetings have been held in Tatranska Lomnica (Czechoslovakia); Liege (Belgium); Ithaca, New York (U. S. A); and London (Great Britain). IAU Symposium 131 was sponsored by IAU Commision 34, on Interstellar Matter and co-sponsored by IAU Commisions 35 and 36 on Stellar Constitution and Theory of Stellar Atmospheres. The symposium was held at the Universidad Nacional Autonoma de Mexico in Mexico City, October 5-9, 1987. It took place in one of the old buildings of the University of Mexico in the downtown area. The inner patio of the building provided very pleasant surroundings for the poster sessions and for extensive discussions among the participants. The meeting was attended by 160 scientists from 22 countries. The Scientific Organizing Committee,under the chairmanship of J.B. Kaler, prepared a comprehensive scientific program based on a set of invited presentations. All contributed papers were presented in poster form. The Scientific Organizing Committee would like to thank the staff of the University of Illinois Department of Astronomy: Dr. Ron Allen for granting financial support; Carol Stickrod, Louise Browning, Deana Griffin and Sandie Osterbur for their help with the organization. IAU provided economic assistance to a group of young astronomers.

Inhalt

I. Observational Data on Nebulae: Invited presentations.- Recent UV and Optical Observations of Planetary Nebulae.- Infrared Observations of Galactic Planetary Nebulae.- Radio Images of Planetary Nebulae.- New and Misclassified Planetary Nebulae.- Catalogues of Planetary Nebulae.- Contributed presentations.- Narrow Band Photometry and Mapping of the Planetary Nebulae NGC 6210 and NGC 7009.- New Observations of Planetary Nebulae S22 and YM29.- Two Southern Low Excitation Planetary Nebulae.- Spectroscopic Survey of Planetary Nebulae.- The Probable Low Excitation Planetary Nebula M3-44.- Optical and Infrared Observations of the Peculiar Planetary Nebula He2-442.- The Photometric (UBV) Study of the Planetary Nebula Variability in 1968 - 1987.- The Photometric and Spectral Variability of the Planetary Nebula IC 4997.- Planetary Nebula He 2-467 Turned out to be the Symbiotic Star with a Period about 500 Days..- Infrared Energy Distribution of Selected Planetary Nebulae.- Near Infrared Photometry of Compact Planetary Nebulae.- The Near Infrared Spectrum of NGC 7027.- A VLA Radio Continuum Survey of Planetary Nebulae.- A New Planetary Nebula.- Is NGC 2242 a New Planetary Nebula?.- Planetary Nebulae Near the Galactic Center I: Method of Discovery and Preliminary Results.- An Infrared Search for New Planetary Nebulae.- II. Nebular Properties: Invited papers.- Distances to Planetary Nebulae.- Galactic Distribution, Radial Velocities and Masses of PN.- The Shapes and Shaping of Planetary Nebulae.- Expansion Velocities and Characteristics of Galactic Planetary Nebulae.- Multiple Shell Planetary Nebulae.- Dust in Planetary Nebulae.- Molecules and Neutral Hydrogen in Planetary Nebulae.- Abundances in Planetary Nebulae.- Photoionization Models.- Contributed papers.- Planetary Nebulae and the Galactic Bulge.- Spectroscopic Distances to Central Stars of Planetary Nebulae.- Investigation of two Planetary Nebulae and their Angular Vicinity in Cygnus.- Structure and Morphology of NGC 6369.- H2 and H I Emission Line Imaging of the Ring Nebula NGC 6720.- Deep Narrow Band Interference Filter Photographs of Selected Extended Planetary Nebulae.- CCD Images of Selected Planetary Nebulae.- CCD Images of Soutern Hemisphere Planetary Nebulae.- IRAS Observations of Extended Planetary Nebulae.- Nebular Density Distributions; A Critical Look.- The Temperature Structure of NGC 7027.- The Display and Manipulation of PN Images on a IBM PC or Compatible.- Infrared Images and Line Profiles of Planetary Nebulae.- NGC 2899: An Evolved Bipolar Planetary Nebula.- The Structure and Kinematics of Bipolar Planetary Nebulae.- Collimated Outflows in Planetary Nebulae.- Kinematical Properties of Planetary Nebulae.- Kinematics of Abell 30.- High Resolution Long Slit Spectroscopy of A78.- The Structure and Velocity Field of A78.- Spatial Deconvolution of IRAS Observations of Planetaries.- Evidence of Expansion Velocity in the Central Region of NGC 2346.- Unusual Emission Line Profiles of M 1-1.- Emission Line Profiles in the Planetary Nebulae IC 4593 and NGC 6153.- A New Study of Some Galactic Planetary Nebulae.- Expansion Velocities of [N II] and [O III] from Compact Planetary Nebulae.- High and Low Resolution Spectra of Selected Planetary Nebulae.- The Planetary ESO 166 - PN21.- The Structure of NGC 2392.- High Velocity Outflows in Post-Main Sequence Nebulae.- Long-Slit 2-Dimensional Spectra of the Giant Halos Around NGC 6543 and NGC 6826.- The Halos of NGC 6543 and NGC 6826.- Expansion Velocities of Southern Planetary Nebulae.- Detection of an Extended Optical Halo around IC 418.- Internal Motions of Faint PN Halos.- Spectroscopic Investigations of Halos of Planetary Nebulae.- Kinematic Structure and Chemical Composition of the Double Shell PN NGC 3242.- Thermal Infrared Emission by Dust in the Planetary Nebula NGC 3918.- The Dust Content of Planetary Nebulae with Neutral Halos.- Spatially Resolved Observations of the Unidentified Dust Features in BD+30 3639.- Observations of CO and HCN (J=1-0) in NGC 2346 and NGC 7293 with the Nobeyama 45m Telescope.- A Young Planetary Nebula with OH Molecules: NGC 6302.- CO in the Bipolar Nebula NGC 2346.- Fluorescent H2 Emission in the Planetary Nebulae BD+30 3639 and Hb 12.- Molecular Hydrogen Emission from Cold Condensations in NGC 2440.- The Systematics and Distribution of Molecular Hydrogen in Planetary Nebulae.- Detection of OH Maser Emission at 1667 MHz from IC 4997.- OH Maser Emission from Young Planetary Nebulae.- Helium Abundances in Gaseous Nebulae.- Collisional Excitation of the 10830 He I Line and the Population of the 23S He I State in Gaseous Nebulae.- Planetary Nebulae and the Pregalactic Helium Abundance.- N/O Abundances in Planetary Nebulae from Far-Infrared Line Observations.- Investigations of DDDM-1; The Fourth Halo Planetary Nebula.- The Peculiar Planetary Nebula M1-78.- Oxygen Depletion Variations in Planetary Nebulae and Shells Ejected from Luminous Population I Stars.- Magnesium Abundances in Planetary Nebulae and Interstellar Absorption of Mg II ?2800 A.- Abundances of C, N and 0 in Planetary Nebulae.- Some Statistics of Nebular Chemical Compositions.- Electron Densities in Planetary Nebulae.- Low Resolution Spectroscopy of 13 Low Surface Brightness PN's.- Effect of Density Variations on Elemental Abundance Determinations in Gaseous Nebulae.- A Possible Subdivision of Type II Planetary Nebulae.- Observations and Models of the "Helix" Nebula NGC 7293.- A Photoionization Model Study of NGC 7027.- Emission Lines of C I and N II in Planetary Nebulae.- The Continuum Emission from Planetary Nebulae.- Comparison of Different Treatments of the Radiation Transfer in Model Calculations of Planetary Nebulae.- The Spatial Distribution of Line Ratio O III/O II in High Excitation Planetary Nebulae.- III. Central Stars: Invited papers.- Magnitudes, Spectra and Temperatures of Planetary Nuclei.- Wind Features and Wind Velocities.- Close-Binary and Pulsating Central Stars.- Binarity and Intrinsic Variability in Central Stars of PN.- Model Atmospheres and Quantitative Spectroscopy of Central Stars of Planetary Nebulae.- Mass Loss Rates in Central Stars of Planetary Nebulae.- Contributed papers.- The Central Star of NGC 7027.- Magnitude Measurements of Central Stars of Planetary Nebulae.- Stromgren Photometry of the Central Stars of Planetary Nebulae.- New Identifications of Faint Central Stars in Extended PN.- Einstein X-ray Observations of Planetary Nebulae and their Implications.- The Origin of the Zanstra Discrepancy: UV Excess in the Central Star Contin…