This IAU Symposium 176 on the topic “Stellar Surface Structure” provided a much needed opportunity for instrumentalists, observers, and theoreticians to present their exciting new results and to preview the even more exciting future for high-resolution imaging of stellar surfaces. I will attempt a critical summary of this symposium by calling attention to those areas that will likely be very productive in the future and by discussing some important topics that have not been addressed adequately to date, such as the roles of systematic and random errors, the true nature of the solar-stellar connection, and the physical processes responsible for stellar surface structure.

Lesser artists borrow, great artists steal. Igor Stravinsky

You never can tell. George Bernard Shaw

One- and two-component models for the Chandler motion are investigated with the use of historical data. Evidence for a two-component motion is more convincing from both the data-analysis and the geophysical point of view.

Fullerenes and their derivatives are amongst the most stable carbonaceous species known and have therefore been proposed as ideal candidates to carry some of the diffuse interstellar bands (DIBs). Evidence for these species in space first came from a few DIBs that have been tentatively identified with electronic transitions of C60+; in recent years, infrared observations have furthermore revealed fullerenes in a variety of circumstellar and interstellar environments. With the presence of the fullerene family in space established, we review what is known about cosmic fullerenes and their derivatives and what role they could play as potential DIB carriers.

Wide-angle, moderately deep redshift surveys such as that conducted as part of the Sloan Digital Sky Survey (SDSS) allow study of the relationship between the structural elements of the large-scale distribution of galaxies – including groups, cluster, superclusters, and voids – and the dependence of galaxy formation and evolution on these enviroments. We present a progress report on mapping efforts with the SDSS and discuss recently constructed catalogs of clusters, voids, and void galaxies, and evidence for a $420h^{-1}$Mpc supercluster or “Great Wall.” Analysis of multi-band photometry and moderate-resolution spectroscopy from the SDSS reveals environmental dependence of the star formation history of galaxies that extends over more than a factor of 100 in density, from clusters all the way to the deep interiors of voids. On average, galaxies in the rarified environments of voids exhibit bluer colors, higher specific star formation rates, lower dust content, and more disk-like morphology than objects in denser regions. This trend persists in comparisons of samples in low vs. high-density regions with similar luminosity and morphology, thus this dependence is not simply an extension of the morphology-density relation. Large-scale modulation of the halo mass function and the temperature of the intergalactic medium might explain this dependence of galaxy evolution on the large-scale environment.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

ISO has shown that the mid–IR spectra of almost all sources are dominated by narrow emission features collectively known as the UIR bands. These bands are carried by a family of polycyclic aromatic hydrocarbon molecules containing about 50 C-atoms. Other classes of molecules such as C-chains as well as non-aromatic groups attached to the PAHs are much less abundant. ISO has revealed that the UIR spectrum is incredibly rich with a large number of weaker features, subfeatures, and shoulders; many of which were not known before. Some examples and the new insights they can provide are described. A systematic study of this spectral structure may well allow us to considerably narrow down the composition of the family of PAHs responsible for the observed emission.

Recent theoretical studies of the consequences of fierce tidal interactions between galaxies are reviewed and compared.

Quasar absorption lines have long been recognised to be a sensitive probe of the abundances, physical conditions, and kinematics of gas in a wide variety of environments including low-density intergalactic regions that probably cannot be studied by any other means. While some pre-Hubble Space Telescope (HST) observations indicated that Mg II absorption lines arise in gaseous galactic halos with a large covering factor, many early QSO absorber studies were hampered by a lack of information about the context of the absorbers and their connections with galaxies. By providing access to crucial ultraviolet resonance lines at low redshifts, deployment of HST and the Far Ultraviolet Spectroscopic Explorer enabled detailed studies of the relationships between QSO absorbers and galaxies. The advent of large surveys such as the Sloan Digital Sky Survey (SDSS) has also advanced the topic by greatly improving the size of absorber and galaxy samples. This paper briefly reviews some observational results on absorber-galaxy connections that have been obtained in the HST/SDSS era, including Mg II absorbers, the low$-z$ Ly$\alpha$ forest, Lyman limit and damped Ly$\alpha$ absorbers, and O VI systems.

Pathways leading to the formation of complex organic molecules are described. Gas-phase processes that may build large carbon-chain species in cold molecular clouds are summarised. Catalytic reactions on grain surfaces can lead to a large variety of organic species, and model calculations of mantle formation by atom additions to multiply-bonded molecules are presented. The subsequent desorption of these mixed molecular ices can initiate a distinctive organic chemistry via ion-molecule pathways. The predictions of this theory are briefly compared with observations to show how possible organic formation pathways in the interstellar medium may be constrained.

From the material gathered during the ‘Cooperative Study of Solar Active Regions’, we studied the flare locations in AR magnetic structure, and flare relations to changes in the magnetic fields and spot configurations. Besides a confirmation of previous results, we find that flares are often associated with two features of the spot configuration evolving in opposite senses, one growing, the other declining.

The latest table of molecular abundances in the cold, dark clouds TMC-1 and L134N is presented. Molecular abundance variations between TMC-1 and L134N, those within TMC-1 and L134N, and those among 49 dark cloud cores surveyed by Suzuki et al. (1991) are interpreted as an effect of chemical evolution.

Recent results for the old and intermediate-age star clusters of the Magellanic Clouds are reviewed. Highlights include new evidence that the LMC old clusters are as old the Galaxy's halo globular clusters and the persistence of the LMC cluster “Age Gap” despite field star evidence for significant star formation during the cluster age gap epoch. For the SMC new data confirm the lack of significant change in cluster abundances with age prior to ~4 Gyr ago.

The sources of information and uncertainties in the intrinsic stellar parameters of luminosity, effective temperature, mass, composition and mass loss rates are discussed. These are used to compare the observed positions of massive stars in the Hertzsprung-Russell Diagram (HRD) with evolutionary tracks. The current status of this effort is briefly reviewed. A short summary of the kinematic properties of massive stars is made. A preliminary but fairly extensive discussion of the distributions and numbers of O-type and Wolf-Rayet stars in the galaxy and other members of the local group is then given.

We review the theory of the formation and gravitational collapse of magnetized molecular cloud cores, leading to the birth of T Tauri stars surrounded by quasi-Keplerian disks whose accretion is driven by the magnetorotational instability (MRI). Some loss of magnetic flux during the collapse results typically in a dimensionless mass-to-flux ratio for the star plus disk of λ0 ≈ 4. Most of the mass ends up in the star, while almost all of the flux and the angular momentum ends up in the disk; therefore, a known mass for the central star implies a computable flux in the surrounding disk. A self-contained theory of the MRI that drives the viscous/resistive spreading in such circumstances then yields the disk radius needed to contain the flux trapped in the disk as a function of the age t. This theory yields analytic predictions of the distributions with distance ϖ from the central star of the surface density Σ(ϖ), the vertical magnetic field Bz(ϖ), and the (sub-Keplerian) angular rotation rate Ω (ϖ). We discuss the implications of this picture for disk-winds, X-winds, and funnel flows, and we summarize the global situation by giving the energy and angular-momentum budget for the overall problem.

It is difficult to prepare an invited paper on topics which are ABC for any specialist in Solar Physics. I considered my task as a systematization of a lot of information about cyclic and secular variations of solar activity rather than an account of new striking results in order to illustrate a certain concept. I beg your pardon in advance for possible defects in my report and for lack of time to quote all related papers.

Rotation affects all the outputs of the evolution and nucleosynthesis of massive stars. We discuss the evolution of the rotational velocities, the internal ω-gradients, the tracks in the H-R diagram, the age determinations, the evolution of the surface N/C abundance ratios, the B/R number ratios of blue to red supergiants and the lifetimes in the WR stages.

This paper presents physical properties of interplanetary dust determined by in-situ techniques. It is probable that, like millimeter-sized meteoroids (Jacchia, et al. 1967), most interplanetary dust is cometary matter. Although a cometary origin for interplanetary dust is widely accepted (Whipple 1967) (Millman, 1972) there is currently no unambiguous proof of this hypothesis. The results presented here must be interpreted accordingly. It must also be remembered that even if interplanetary particles are cometary, they might possibly be altered in the interplanetary medium by collisions and by thermal effects during close perihelion passages, so the dust particles may not be representative of unaltered cometary material.

The THEMIS telescope will provide high resolution observations of the solar vector magnetic field. We present some capabilities of this instrument, concerning the polarization analysis, the correlation tracker and the two spectrographs. THEMIS is expected to come into operation in 1995–1996.

We present the imaging potential of a tomographic technique which combines time-resolved spectroscopy and long baseline interferometry, providing information that cannot be obtained otherwise with each of these techniques separately.