Systematic efforts of monitoring starspots from the middle of the XXth century, and the results obtained from the datasets, are summarized with special focus on the observations made by automated telescopes. Multicolour photometry shows correlations between colour indices and brightness, indicating spotted regions with different average temperatures originating from spots and faculae. Long-term monitoring of spotted stars reveals variability on different timescales.

On the rotational timescale new spot appearances and starspot proper motions are followed from continuous changes of light curves during subsequent rotations. Sudden interchange of the more and less active hemispheres on the stellar surfaces is the so called flip-flop phenomenon. The existence and strength of the differential rotation is seen from the rotational signals of spots being at different stellar latitudes.

Long datasets, with only short, annual interruptions, shed light on the nature of stellar activity cycles and multiple cycles. The systematic and/or random changes of the spot cycle lengths are discovered and described using various time-frequency analysis tools. Positions and sizes of spotted regions on stellar surfaces are calculated from photometric data by various softwares. From spot positions derived for decades, active longitudes on the stellar surfaces are found, which, in case of synchronized eclipsing binaries can be well positioned in the orbital frame, with respect to, and affected by, the companion stars.

When the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft enters orbit about Mercury in March 2011 it will begin a new phase in an age-old scientific study of the innermost planet. Despite being visible to the unaided eye, Mercury's proximity to the Sun makes it extremely difficult to observe from Earth. Nonetheless, over the centuries man has pursued a quest to understand the elusive planet, and has teased out information about its motions in the sky, its relation to the other planets, and its physical characteristics. A great leap was made in our understanding of Mercury when the Mariner 10 spacecraft flew past it three times in the mid-1970s, providing a rich set of close-up observations. Now, three decades later, The MESSENGER spacecraft has also visited the planet three times, and is poised to add significantly to the study with a year-long orbital observation campaign.

The standard picture of planet formation posits that giant gas planets are over-grown rocky planets massive enough to attract enormous gas atmospheres. It has been shown recently that the opposite point of view is physically plausible: the rocky terrestrial planets are former giant planet embryos dried of their gas “to the bone” by the influences of the parent star. Here we provide a brief overview of this “Tidal Downsizing” hypothesis in the context of the Solar System structure.

The Solar System formation PFO–CFO hypothesis is developed in the direction of creation of a phenomenological model focused on solution of a number of paradoxes and answering to a number of mysterious questions under the same cover. For explanation of the events and processes that occurred over the period from the middle ages of the pre-solar star to the Solar System formation, original approaches are applied.

Classical Be stars are rapidly rotating, hot stars that possess an equatorial disk formed from gas released by the central star. The mechanism driving the stellar mass loss has yet to be fully explained, but the rapid rotation of the central B star is believed to be crucial. Rapid rotation also produces gravity darkening, and we have now extended our disk models to include these effects. In this contribution, we focus on the effect of gravity darkening on the thermal structure of a circumstellar disk.

The meeting was opened by Ted Bowell, president, at 11 am. The 2006 Division III meetings were reviewed by Guy Consolmagno, secretary; as the minutes of those meetings have already been published, they were assumed to be approved.

We present various instability mechanisms in the accreting black hole systems which might indicate at the connection between the accretion disk and jet. The jets observed in microquasars can have a peristent or blobby morphology. Correlated with the accretion luminosity, this might provide a link to the cyclic outbursts of the disk. Such duty-cycle type of behaviour on short timescales results from the thermal instability caused by the radiation pressure domination. The same type of instability may explain the cyclic radioactivity of the supermassive black hole systems. The somewhat longer timescales are characteristic for the instability caused by the partial hydrogen ionization. The distortions of the jet direction and complex morphology of the sources can be caused by precession of the disk-jet axis.

Warps are a basic feature of disk galaxies. Usually they occur at radii where the optical disk fades and become most pronounced in the outermost gaseous disks.

As such, warps present a massive reservoir to replenish star forming material in the inner, star forming disks. Furthermore, some possible excitation mechanisms for warps connect their formation to the accretion of extragalctic material. Interactions or mergers with gas-rich companions or the direct accretion of the ambient intergalactic medium might lead to the formation of warps, at the same time supplementing fuel to maintain star formation in galactic disks.

Employing a number of H i studies of warped galaxies, including ultra-deep observations of the prototype warped galaxies NGC 5907 and NGC 4013, I discuss whether the observed kinematics may show evidence for a connection of warps and accretion from the ambient medium.

Massive stars influence the surrounding universe far out of proportion to their numbers through ionizing radiation, supernova explosions, and heavy element production. Their formation requires the collapse of massive interstellar gas clouds with very high accretion rates. We discuss results from the first three-dimensional simulations of the gravitational collapse of a massive, rotating molecular cloud core that include heating by both non-ionizing and ionizing radiation. Local gravitational instabilities in the accretion flow lead to the build-up of a small cluster of stars. These lower-mass companions subsequently compete with the high-mass star for the same common gas reservoir and limit its overall mass growth. This process is called fragmentation-induced starvation, and explains why massive stars are usually found as members of high-order stellar systems. These simulations also show that the H ii regions forming around massive stars are initially trapped by the infalling gas, but soon begin to fluctuate rapidly. Over time, the same ultracompact H ii region can expand anisotropically, contract again, and take on any of the observed morphological classes. The total lifetime of H ii regions is given by the global accretion timescale, rather than their short internal sound-crossing time. This solves the so-called lifetime problem of ultracompact H ii region. We conclude that the the most significant differences between the formation of low-mass and high-mass stars are all explained as the result of rapid accretion within a dense, gravitationally unstable flow.

Galaxy interactions and mergers play a significant, but still debated and poorly understood role in the star formation history of galaxies. Numerical and theoretical models cannot yet explain the main properties of merger-induced starbursts, including their intensity and their spatial extent. Usually, the mechanism invoked in merger-induced starbursts is a global inflow of gas towards the central kpc, resulting in a nuclear starburst. We show here, using high-resolution AMR simulations and comparing to observations of the gas component in mergers, that the triggering of starbursts also results from increased ISM turbulence and velocity dispersions in interacting systems. This forms cold gas that are denser and more massive than in quiescent disk galaxies. The fraction of dense cold gas largely increases, modifying the global density distribution of these systems, and efficient star formation results. Because the starbursting activity is not just from a global compacting of the gas to higher average surface densities, but also from higher turbulence and fragmentation into massive and dense clouds, merging systems can enter a different regime of star formation compared to quiescent disk galaxies. This is in quantitative agreement with recent observations suggesting that disk galaxies and starbursting systems are not the low-activity end and high-activity end of a single regime, but actually follow different scaling relations for their star formation.

This report of the business meeting of Commission 15 at the 2009 IAU GA is based on notes provided by Walter Huebner, past president, and on the minutes taken by Daniel Boice, secretary of Commission 15 in the triennium 2006 to 2009, with additional notes from the current secretary, Daniel Hestroffer. The business meeting was split into two sessions, the first held on 5 August and the second held on 11 August. This report presents the minutes of the two Commission 15 business-meeting sessions held during General Assembly XXVII.

Jets can contribute to the spectra of X-ray binaries (XRBs) and active galactic nuclei (AGN) from the radio through the γ-ray bands; thus understanding their physics is key for interpreting the data. Recent VLBI observations suggest that jets begin to accelerate particles into power-law distributions at a point offset from the black hole by ~104rg, possibly via a collimation shock. Spectral fitting of simultaneous, broadband data from both XRBs and AGN in jet-dominated states corroborates this picture. From a magnetohydrodynamical (MHD) point of view, it is natural to associate the onset of particle acceleration with the final MHD critical point in the flow, the modified fast point (MFP), where causal contact with the upstream flow is broken. In this way a standing disruption like a shock can form, and this location might vary with the physical parameters of the jet. In order to study this issue, we have used the self-similar formalism of Vlahakis & Königl (2003, hereafter VK03) to simplify the MHD equations and to derive solutions that cross the critical points. We have found a new parameter space of solutions that cross the MFP at a finite height above the disc and are relativistic, spanning a range of Lorentz factors Γ ≤ 10 (Polko et al. 2010). We present these results, as well as preliminary work connecting the relativistic formalism to the non-relativistic conditions with gravity near the base of the jets.

Radio astronomy, broadly interpreted, has made important contributions to the study of galaxy formation and evolution. Maps of the cosmic microwave background provide information on the seeds of large-scale structure, in addition to refined values of the cosmological parameters. Examples of contributions from more conventional radio astronomy include:–The use of radio observations to track star formation rates since they are not affected by dust obscuration as optical/UV observations are, and the use of molecular line observations to make purely “radio” redshift determinations.

One of the challenges in constructing global magnetohydrodynamic (MHD) models of the inner heliosphere for, e.g., space weather forecasting purposes, is to correctly capture the acceleration and expansion of the solar wind. In many current models, the solar wind is driven by varying the polytropic index so that a desired heating is obtained. While such schemes can yield solar wind properties consistent with observations, they are not problem-free. In this work, we demonstrate by performing MHD simulations that altering the polytropic index affects the properties of propagating shocks significantly, which in turn affect the predicted space weather conditions. Thus, driving the solar wind with such a mechanism should be used with care in simulations where correctly capturing the shock physics is essential. As a remedy, we present a simple heating function formulation by which the polytropic wind can be used while still modeling the shock physics correctly.

Recent observational and theoretical arguments suggest that magnetic OB stars may suffer more mixing than their non magnetic analogs. We present the results of an NLTE abundance study revealing a lack of CN-cycled material at the surface of two magnetic stars discovered by the MiMeS project (NGC2244 #201 and HD 57682). The existence of a strong magnetic field is therefore not a sufficient condition for deep mixing in main-sequence OB stars.

Stars form predominantly in clusters inside dense clumps of molecular clouds that are both turbulent and magnetized. The typical size and mass of the cluster-forming clumps are ~1 pc and ~102 – 103 M⊙, respectively. Here, we discuss some recent progress on numerical simulations of clustered star formation in such parsec-scale dense clumps with emphasis on the role of magnetic fields. The simulations have shown that magnetic fields tend to slow down global gravitational collapse and thus star formation, especially in the presence of protostellar outflow feedback. Even a relatively weak magnetic field can retard star formation significantly, because the field is amplified by supersonic turbulence to an equipartition strength. However, in such a case, the distorted field component dominates the uniform one. In contrast, if the field is moderately-strong, the uniform component remains dominant. Such a difference in the magnetic structure is observed in simulated polarization maps of dust thermal emission. Recent polarization measurements show that the field lines in nearby cluster-forming clumps are spatially well-ordered, indicative of a rather strong field. In such strongly-magnetized clumps, star formation should proceed relatively slowly; it continues for at least several global free-fall times of the parent dense clump (tff ~ a few × 105 yr).

A-type stars have both a near-surface layer of fast convection that can excite acoustic modes and a deep zone of core convection whose properties may be probed with asteroseismology. Many A-type stars also exhibit large magnetic spots that are often attributed to surviving primordial fields of global scale in the intervening radiative zone. We have explored the potential for core convection in rotating A-type stars to build strong magnetic fields through dynamo action. These 3-D simulations using the ASH code provide guidance on the nature of differential rotation and magnetic fields that may be present in the deep interiors of these stars, thus informing the asteroseismic deductions now becoming feasible. Our models encompass the inner 30% by radius of a two solar mass A-type star, rotating at four times the solar rate and capturing the convective core and a portion of the overlying radiative envelope. Convection in these stars drives a strong retrograde differential rotation and yields a core that is prolate in shape. When dynamo action is admitted, the convection generates strong magnetic fields largely in equipartition with the dynamics. Remarkably, introducing a modest but large-scale external field threading the radiative envelope (which may be of primordial origin) can substantially alter the turbulent dynamics of the convective interior. The resulting convection involves a complex assembly of helical rolls that link distant portions of the core and stretch and advect magnetic field, ultimately yielding magnetic fields of super-equipartition strength.

The four giant planets - Jupiter, Saturn, Uranus and Neptune - have common properties which make them very different from the terrestrial planets: located at large distances from the Sun, they have big sizes and masses but low densities; they all have a ring system and a large number of satellites. These common properties can be understood in the light of their formation scenario, based upon the accretion of protosolar gas on an initial icy core. Giant planets have been explored by space missions (Pioneer 10 and 11, Voyager 1 and 2, Galileo and Cassini) but also by Earth-orbiting satellites and ground-based telescopes. There are still open questions related to the origin and evolution of the giant planets, in particular their moderate migration, the origin of the cold planetesimals which formed Jupiter, the origin of the atmospheric dynamics in Jupiter and Saturn, and the differences in the internal structures of Uranus and Neptune.

We review the observational knowledge that has built up over the past 25 years on the interstellar magnetic field within ~ 150 pc of the Galactic center. We also provide a critical discussion of the main observational findings and comment on their possible theoretical interpretations. To conclude, we propose a coherent view of the interstellar magnetic field near the Galactic center, which accounts at best for the vast body of observations.

Brown dwarfs and massive planets have similar structures, and there is probably an overlap in mass between the most massive planets and the lowest mass brown dwarfs. This raises questions as to what extent the structures of the most massive planets and lowest mass brown dwarfs differ, and what similarities (or not) there might be between their formation mechanisms. Here I discuss these issues on the background of recent numerical simulations of star formation, new evidence from cosmochemistry about the conditions in the early solar system, and recently discovered mechanisms that can expedite planetesimal and possibly planet formation greatly.