We discuss measurements of disk mass from non-circular streaming motions of gas in the barred galaxies NGC 3095 and NGC 4123. in these galaxies with strong shocks and non-circular motions, the inner regions must be disk-dominated to reproduce the shocks. This requires dark matter halos of low central density and low concentration, compared to LCDM halo predictions. in addition, the baryonic collapse to a disk should have compressed the halo and increased the dark matter density, which sharpens the disagreement. One possible resolution is a substantial amount of angular momentum transfer from disk to halo, but this is not particularly attractive nor elegant.

The study of proto-planetary nebulae (PPNs) leads to a better understanding of both the preceding asymptotic giant branch and the succeeding planetary nebula phases of stellar evolution. Recent results are reviewed, emphasizing the properties of the central stars and the shape and chemistry of the nebulae. The study of PPNs is seen to be important in its own right.

Computations of AGB stellar evolution which include the effects of mass loss are still relatively rare. However, in order to relate numbers of Mira variables, OH/IR stars and carbon stars to associated stellar populations, it is necessary to understand evolutionary timescales on the AGB.

The dominant factors controlling very late AGB evolution are shell flashes and mass loss, and some quantitative estimate of the latter is needed for stellar evolution calculations. The favoured mechanism for the production of the large mass loss rates observed in late AGB stars such as OH/IR stars and dust-enshrouded carbon stars, which have mass loss rates up to a few times 10−5 M⊙ yr−1 (see van der Veen and Rugers 1989 for a compilation), is a dual process involving the lévitation of matter above the photosphere by large-amplitude radial pulsation followed by the formation of grains on which radiation pressure acts to drive the circumstellar material away from the star (Castor 1981; Holzer and MacGregor 1985; Hearn 1990). The studies by Wood (1979) and Bowen (1988) show that, by themselves, neither pulsation nor radiation pressure acting on grains can produce the very large mass loss rates from AGB stars.

The linear polarization of comets depends upon the cometary dust physical properties, as well as upon the phase angle and the wavelength. The observed similarities and discrepancies provide drastic constraints on the physical properties of the dust. A series of measurements of light scattering properties on clouds of particles and of the aggregates they form under microgravity conditions should allow the interpretation of the observations in terms of physical properties of the dust.

The newly established Inter-Union Commission on Solar-Terrestrial Physics (IUCSTP) has inquired of selected experts about actions useful in the period of the next solar maximum, which need an organization and coordination on international basis. These inquiries have shown that one of the problems, in which a broad international cooperation might lead to substantial improvement of scientific results, is the coordination of ground-base and space-vehicle observations of the Sun and its active phenomena.

Therefore, in order to help the IUCSTP in its preparatory work, the chairmen of IAU Commissions 10 (Solar Activity) and 44 (Observations from outside the Atmosphere) agreed to hold a joint meeting of these two Commissions during the IAU Assembly in Prague, on ‘Coordination of solar observations made at ground-base Observatories and with space vehicles’. It was anticipated that other IAU members interested in this problem, particularly members of Commissions 12 and 40, would also take part in the discussion.

The notion that December 21, 2012 will bring physical catastrophes, a transformation of consciousness, or even a New Age is an unanticipated and unintentional consequence of early speculation by credentialed academic experts. It has grown as a result of its subsequent interpretation through the lens of speculative, counterculture metaphysics by individuals with both academic and non-academic backgrounds. This article provides a historical review of the most significant contributions to the emergence of the 2012 phenomenon.

A defining property of massive stars is the dominant, dynamical role played by radiation throughout the stellar interior, atmosphere, and wind. Associated with this radiation hydrodynamics are several distinct kinds of instabilities that can lead to convection in both core and envelope, clumping in atmosphere and wind outflow, and perhaps even the dramatic mass loss outbursts associated with Luminous Blue Variable phases. Here I review these instabilities with emphasis on basic physical properties of radiative driving. I draw on two specific examples of dynamical instability, namely the strong instability associated with line-driving of a stellar wind outflow, and the global stellar instabilities associated with approaching or exceeding a modified Eddington limit. I conclude with a brief mention of recent ideas on the role of stellar rotation in the shaping of bipolar LBV outbursts.

In this paper, we discuss the Be stars which show recurrent shell structure and/or cyclic variations in the profiles of their emission lines with periods near 100d and, thus, are good candidates for interacting binaries undergoing mass-exchange. The periodic spectral variations observed in the Ble star HR 2142 are reviewed and brought up to date in the light of recent observations. HR 2142 is then compared with other periodic binary Be stars (AX Mon, 17 Lep, HD 218393, HD 173219, and φ Per) in order to point out the wide variance in observed spectra which interacting binaries can display.

Objective-prism surveys for UV-excess and emission-line objects, especially the First and Second Byurakan Surveys, have been central to the study of active galactic nuclei (AGNs). We review previous line-selected surveys for AGNs and discuss their contribution to our understanding of the AGN phenomena. In addition, we present results from the KPNO International Spectroscopic Survey, a modern digital objective-prism survey for emission line objects. This survey is discovering substantial numbers of new AGNs, in particular low-luminosity AGNs and LINERs.

Solar features that exhibit chirality are: fibril patterns in filament channels, filaments, coronal arcades over filaments, superpenumbral fibrils exterior to sunspots, whole active regions observed with magnetographs, some large-scale X-ray structures, and interplanetary magnetic plasma clouds originating from coronal mass ejections. Their signatures of chirality are briefly reviewed; some details are mentioned to further show relationships which link all of the chirality patterns into a single framework. The helicity of solar magnetic fields is the evident physical phenomena which finks each of the seven features to each other and into a broader framework. The chirality system, viewed as a whole magnetic system, reveals: (1) a consistent rotational configuration of the dominant direction of the magnetic field with height of features within and over filament channels from the photosphere to the highest part of the solar corona, and (2) the prominence cavity as a unique space between magnetic fields of opposite helicity.

There are about 70 Galactic supernova remnants (SNRs) that are now confirmed or suggested to be in physical contact with molecular clouds (MCs) with six kinds of evidence of multiwavelength observations. Recent detailed CO-line spectroscopic mappings of a series of SNRs reveal them to be in cavities of molecular gas, implying the roles the progenitors may have played. We predict a linear correlation between the wind bubble sizes of main-sequence OB stars in a molecular environment and the stellar masses and discuss its implication for supernova progenitors. The molecular environments of SNRs can serve as a good probe for the γ-rays arising from the hadronic interaction of the accelerated protons, and this paper also discusses the γ-ray emission from MCs illuminated by diffusive protons that escape from SNR shocks.

Laser tracking of the Lageos spacecraft has been used to derive the position of the Earth's pole of rotation at 5-day intervals during October, November and December 1976. The estimated precision of the results is 0.01 to 0.02 arcseconds in both x and y components, although the formal uncertainty is an order of magnitude better, and there is general agreement with the Bureau International de l'Heure smoothed pole path to about 0.02 arcseconds. Present orbit determination capability of Lageos is limited to about 25 cm rms fit to data over periods of 5 days and about 50 cm over 50 days. The present major sources of error in the perturbations of Lageos are Earth and ocean tides followed by the Earth's gravity field, and solar and Earth reflected radiation pressure. Ultimate accuracy for polar motion and Earth rotation from Lageos after improved modeling of the perturbing forces appears to be of order ± 5 cm for polar motion over a period of about 1 day and about ± 0.2 to ± 0.3 milliseconds in U.T. for periods up to 2 or 3 months.

Rapidly rotating stars are readily produced in binary systems. An accreting star in a binary system can be spun up by mass accretion and quickly approach the break-up limit. Mergers between two stars in a binary are expected to result in massive, fast rotating stars. These rapid rotators may appear as Be or Oe stars or at low metallicity they may be progenitors of long gamma-ray bursts.

Given the high frequency of massive stars in close binaries it seems likely that a large fraction of rapidly rotating stars result from binary interaction. It is not straightforward to distinguish a a fast rotator that was born as a rapidly rotating single star from a fast rotator that resulted from some kind of binary interaction. Rapidly rotating stars resulting from binary interaction will often appear to be single because the companion tends to be a low mass, low luminosity star in a wide orbit. Alternatively, they became single stars after a merger or disruption of the binary system during the supernova explosion of the primary.

The absence of evidence for a companion does not guarantee that the system did not experience binary interaction in the past. If binary interaction is one of the main causes of high stellar rotation rates, the binary fraction is expected to be smaller among fast rotators. How this prediction depend on uncertainties in the physics of the binary interactions requires further investigation.

Presupernova models of massive stars are presented and their explosion by “delayed neutrino transport” examined. A new form of long duration Type II supernova model is also explored based upon repeated encounter with the electron-positron pair instability in stars heavier than about 60 M⊙. Carbon deflagration in white dwarfs is discussed as the probable explanation of Type I supernovae and special attention is paid to the physical processes whereby a nuclear flame propagates through degenerate carbon.

We describe some aspects of implementing star cluster simulations on HARP. The code NBODY4 employs the Hermite scheme with hierarchical block-steps for direct integration. The algorithms have been optimized for parallel processing with the eight pipeline HARP-2 delivering a peak performance of about 1.7 Gflops for N = 104 particles. Hard binaries are studied by KS regularization which also uses the Hermite scheme, whereas strong interactions between 3–5 particles are treated by chain regularization. Astrophysical processes modelled include mass loss by stellar evolution, two-body tidal interaction, Roche lobe mass transfer, common envelope evolution, magnetic braking and gravitational radiation. Consistent values of stellar radii and evolution type are obtained by fast look-up. A new formulation of collision outcomes yields blue stragglers and other exotic objects. Some recent results for an open cluster model are presented.

During their main sequence evolution, massive stars can develop convective regions very close to their surface. These regions are caused by an opacity peak associated with iron ionization. Cantiello et al. (2009) found a possible connection between the presence of sub-photospheric convective motions and small scale stochastic velocities in the photosphere of early-type stars. This supports a physical mechanism where microturbulence is caused by waves that are triggered by subsurface convection zones. They further suggest that clumping in the inner parts of the winds of OB stars could be related to subsurface convection, and that the convective layers may also be responsible for stochastic excitation of non-radial pulsations. Furthermore, magnetic fields produced in the iron convection zone could appear at the surface of such massive stars. Therefore subsurface convection could be responsible for the occurrence of observable phenomena such as line profile variability and discrete absorption components. These phenomena have been observed for decades, but still evade a clear theoretical explanation. Here we present preliminary results from 3D MHD simulations of such subsurface convection.