I review the progress made over the past decade in the measurement of magnetic fields on solar–like stars. I describe the evolution of magnetic analysis techniques, summarize our current understanding of stellar magnetic properties, and outline some future research directions.

The six years of data from the Mt. Wilson Magnetic Atlas were analyzed in terms of surface harmonics. Between 1959 and 1962 the dominant harmonic corresponded to a dipole lying in the plane of the equator (2 sectors). There was also a significant zonal harmonic in which both solar poles had the same magnetic polarity, opposite to that at the equator. From the end of 1962 through 1964, the harmonic corresponding to 4 sectors was dominant. In 1965 and 1966, the harmonic of the north-south dipole became significant.

Seismology has become a powerful tool in studies of the magnetic structure of solar prominences and filaments. Reversely, analytical and numerical models are guided by available information about the spatial and thermodynamical structure of these enigmatic structures. The present invited paper reviews recent observational results on oscillations and waves as well as details about small-scale structures and dynamics of prominences and filaments.

The Deeper Wider Faster programme (DWF) is a project that coordinates more than 30 multi-wavelength and multi-messenger facilities worldwide and in space, in order to detect and study fast transients (durations of milliseconds to hours). DWF has four main components: (1) simultaneous observations, where ∼10 major facilities, from radio to gamma-ray, are coordinated to perform short-cadence, deep, wide-field observations of the same field at the same time. Radio telescopes search for fast radio bursts, while optical imagers and high-energy instruments search for transient events whose time-scales are seconds to hours, (2) supercomputer data processing and candidate identification in real time (seconds to minutes), along with human inspection of candidates, also in real time (minutes), using sophisticated visualisation technology, (3) rapid-response (minutes) follow-up spectroscopy and imaging, and conventional ToO observations, and (4) long-term follow up by a global network of 1-m to 4-m telescopes. The principal goals of DWF are to discover and study counterparts to fast radio bursts and gravitational-wave events, as well as transients at all wavelengths that have durations of milliseconds to hours.

Recent studies of the Galactic center environment have revealed a wealth of new thermal and nonthermal features with unusual characteristics. A system of nonthermal filamentary structures tracing magnetic field lines are found to extend over 200pc in the direction perpendicular to the Galactic plane. Ionized structures, like nonthermal features, appear filamentary and show forbidden velocity fields in the sense of Galactic rotation and large line widths. Faraday rotation characteristics and the flat spectral index distributions of the nonthermal filaments suggest a mixture of thermal and nonthermal gas. Furthermore, the relative spatial distributions of the magnetic structures with respect to those of the ionized and molecular gas suggest a physical interaction between these two systems. In spite of numerous questions concerning the origin of the large-scale organized magnetic structures, the mechanism by which particles are accelerated to relativistic energies, and the source or sources of heating the dust and gas, recent studies have been able to distinguish the inner 200pc of the nucleus from the disk of the Galaxy in at least two more respects: (1) the recognition that the magnetic field has a large-scale structure and is strong, uniform and dynamically important; and (2) the physics of interstellar matter may be dominated by the poloidal component of the magnetic field.

Of the nearly 3900 near-Earth asteroids (NEAs) known as of June 2006, 325 have estimated rotation periods, with most of those determined by lightcurve analysis led by a few dedicated programs. NEAs with diameters down to 10 meters have been sampled. Observed spin distribution shows a major changing point around diameter of 200 meters. Larger NEAs show a barrier against spins faster than 11 d−1 (period about 2.2 h) that shifts to slower rates (longer periods) with increasing lightcurve amplitude (i.e., with increasing equatorial elongation). The spin barrier is interpreted as a critical spin rate for bodies in a gravity regime; NEAs larger than 200 meters are predominantly bodies with tensile strength too low to withstand a centrifugal acceleration for rotation faster than the critical spin rate. The cohesionless spin barrier disappears at sizes less than 200 meters where most objects rotate too fast to be held together by self-gravitation only, so a cohesion is implied in the smaller NEAs.

The distribution of NEA spin rates in the cohesionless size range (D0.2 km) is highly non-Maxwellian, suggesting that mechanisms other than just collisions have been at work. There is a pile up just in front of the barrier, at periods 2–3 h. It may be related to a spin up mechanism crowding asteroids to the barrier. An excess of slow rotators is observed at periods longer than 30 hours. A spin-down mechanism has no obvious lower limit on spin rate; periods as long as tens of days have been observed.

Most NEAs appear to be in their basic spin states with rotation around principal axis with maximum moment of inertia. Tumbling objects (i.e., bodies in excited, non-principal axis rotation) are present and actually predominate among slow rotators with estimated damping timescales longer than the age of the solar system. A few tumblers observed among fast rotating coherent objects appear to be either more rigid or younger than the larger (cohesionless) tumblers.

An abundant population of binary systems has been found among NEAs. The fraction of binaries among NEAs larger than 0.3 km has been estimated to be 15 ± 4%. Primaries of binary systems concentrate at fast spin rates (periods 2–3 h) and low amplitudes, i.e., they lie just below the cohesionless spin barrier. The total angular momentum content in binary systems suggests that they formed from parent bodies spinning at the critical rate. The fact that a very similar population of binaries has been found among small main belt asteroids suggests a binary formation mechanism that may not be related to close encounters with the terrestrial planets.

The asteroids (more precisely: objects of the main asteroid belt) and Kuiper Belt objects (more precisely: objects of the cold classical Kuiper Belt) are leftovers of the building material for our earth and all other planets in our solar system from more than 4.5 billion years ago. At the time of their formation those were typically 100 km large objects. They were called planetesimals, built up from icy and dusty grains. In our current paradigm of planet formation it was turbulent flows and metastable flow patterns, like zonal flows and vortices, that concentrated mm to cm sized icy dust grains in sufficient numbers that a streaming instability followed by a gravitational collapse of these particle clump was triggered. The entire picture is sometimes referred to as gravoturbulent formation of planetesimals. What was missing until recently, was a physically motivated prediction on the typical sizes at which planetesimals should form via this process. Our numerical simulations in the past had only shown a correlation between numerical resolution and planetesimal size and thus no answer was possible (Johansen et al.2011). But with the lastest series of simulations on JUQUEEN (Stephan & Doctor 2015), covering all the length scales down to the physical size of actual planetesimals, we were able to obtain values for the turbulent particle diffusion as a function of the particle load in the gas. Thus, we have all necessary data at hand to feed a 'back of the envelope' calculation that predicts the size of planetesimals as result of a competition between gravitational concentration and turbulent diffusion. Using the diffusion values obtained in the numerical simulations it predicts planetesimal sizes on the order of 100 km, which suprisingly coincides with the measured data from both asteroids (Bottke et al.2005) as well from Kuiper Belt objects (Nesvorny et al.2011).

Present day estimates of the Hubble constant based on Cepheids and on the cosmic microwave background radiation are uncertain by roughly 10% (on the conservative assumption that the universe may not be perfectly flat). Gravitational lens time delay measurements can produce estimates that are less uncertain, but only if a variety of major difficulties are overcome. These include a paucity of constraints on the lensing potential, the degeneracies associated with mass sheets and the central concentration of the lensing galaxy, multiple lenses, microlensing by stars, and the small variability amplitude typical of most quasars. To date only one lens meets all of these challenges. Several suffer only from the central concentration degeneracy, which may be lifted if one is willing to assume that systems with time delays are either like better constrained systems with non-variable sources, or alternatively, like nearby galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

It used to be that interest in the ages of the globular clusters was primarily motivated by cosmological considerations. In recent years, remarkable progress in the quality and quantity of observations and advances in the understanding of stellar atmospheres and in the construction of theoretical isochrones make possible the use of globular clusters as probes of galactic evolution. A new picture, still tentative at this point, is emerging of the formation and chemical enrichment of the halo, in its nucleus and in its outer reaches through observations of globular clusters, dwarf spheroidal galaxies and the Magellanic Clouds.

We review the events leading to the discovery of Herbig-Haro objects half a century ago, and the early efforts to understand the nature of these enigmatic objects. The recognition in the mid-seventies of the shocked nature of HH objects heralded a burst of observational and theoretical efforts, and further impetus was soon after provided by the discovery of high proper motions, and by detailed optical, infrared and ultraviolet spectroscopic studies. The recognition in the early eighties of HH jets was the starting point for the increasingly intense studies during the last 15 years which we discuss in this Symposium. In the second half of our review, we summarize the insights into the nature of HH jets provided by analyzing high resolution images obtained with the Hubble Space Telescope of two of the finest known HH jets, HH 47 and HH 111.

A new determination of the pregalactic helium abundance based on the Magellanic Clouds H II regions is discussed. This determination amounts to Yp = 0.2345 ± 0.0030 and is compared with those derived from giant extragalactic H II regions in systems with extremely low heavy elements content. It is suggested that the higher primordial value derived by other authors from giant H II region complexes could be due to two systematic effects: the presence of neutral hydrogen inside the helium Strömgren sphere and the presence of temperature variations inside the observed volume.

It is argued that an important fraction of PNe present large temperature variations that are not due to observational errors nor to incomplete atomic physics. Seven possible causes for these variations are reviewed, one of them is presented for the first time.

The pinwheel nebulae observed in some WC-binaries essentially mirror a transport phenomenon. We show the importance of the central wind collision zone in setting the ‘initial conditions’ for this transport. In order to understand some of the newly observed features, we postulate that standard theory of colliding flows must be extended by considering radiative breaking, heat-conduction, and the clumped character of the winds. We suggest that clumped winds can be modeled by highly compressible turbulence and outline some consequences for the physics of the wind collision zone. With regard to dust production we argue that the system center is the only location where dust nucleation can happen.

In the recent years revolutionary results concerning the nature of icy dust particles have been obtained with the help of the Infrared Space Observatory (ISO) and ground based observations. To date interstellar ice features of H2O, CO, CO2, CH3OH, CH4, H2CO, OCS and HCOOH as well as other minor species are observed. Interstellar grains act as important catalysts in the interstellar medium. Processes such as UV irradiation, cosmic ray processing and temperature variations determine the grain mantle growth and chemical evolution. ISO has revealed that ice segregation is an important and ubiquitous process in the vicinity of massive protostars and reflects the extensive thermal processing of grains in such environments.

In this paper a recent view on the inventory of interstellar ices is presented. Constraints on the reservoirs of oxygen in dense clouds are discussed, taking into account recent measurements of oxygen-bearing species. Large abundances of CO2 and CH3OH in dense molecular clouds provide challenging perspectives to investigate the differences of ice chemistry in the vicinity of high and low-mass protostars. Accurate abundances of ice species and knowledge on the ice distribution in the protostellar regions are an important tool to define the environmental conditions in molecular clouds. A global understanding of interstellar ice chemistry also allows monitoring the incorporation and evolution of volatiles in planetesimals and comets and to reveal processes predominant in the early Solar System.

Stars with a mass up to a few solar masses are one of the main contributors to the enrichment of the interstellar medium in dust and heavy elements. However, while significant progress has been made, the process of the mass-loss responsible for this enrichment is still not exactly known and forces beyond radiation pressure might be required. Often, the mass lost in the last phases of the stars life will become a spectacular planetary nebula. The shaping process of often strongly a-spherical PNe is equally elusive. Both binaries and magnetic fields have been suggested to be possible agents although a combination of both might also be a natural explanation.

Here I review the current evidence for magnetic fields around AGB and post-AGB stars pre-Planetary Nebulae and PNe themselves. Magnetic fields appear to be ubiquitous in the envelopes of apparently single stars, challenging current ideas on its origin, although we have found that binary companions could easily be hidden from view. There are also strong indications of magnetically collimated outflows from post-AGB/pre-PNe objects supporting a significant role in shaping the circumstellar envelope.

Low-mass stars exhibit, at all stages of their evolution, the signatures of complex physical processes that require challenging modeling beyond standard stellar theory. In this review, we recall the most striking observational evidences that probe the interaction and interdependence of various transport processes of chemicals and angular momentum in these objects. We then focus on the impact of atomic diffusion, large scale mixing due to rotation, and internal gravity waves on stellar properties on the main sequence and slightly beyond.

With the advent of more precise methods for measuring Earth rotation, a number of corrections to the apparent directions in space, to the terrestrial references, and to the rotation axis motion have to be carefully applied. It is the duty of the international Astronomical Union to give recommended or conventional expressions of these corrections in order to avoid inextricable difficulties in discussing the evaluated results. However, this task is not sufficient. The concepts used in the description of the Earth's rotation are somewhat obscured by traditions. They should be purified by removing notions which are not directly relevant.

We discuss the formulation of a new nutation series to be used in the reduction of modern space geodetic data. The motivation for developing such a series is to develop a nutation series that has smaller short period errors than the IAU 1980 nutation series and to provide a series that can be used with techniques such as the Global Positioning System (GPS) that have sensitivity to nutations but can directly separate the effects of nutations from errors in the dynamical force models that effect the satellite orbits. A modern nutation series should allow the errors in the force models for GPS to be better understood. The series is constructed by convolving the Kinoshita and Souchay rigid Earth nutation series with an Earth response function whose parameters are partly based on geophysical models of the Earth and partly estimated from a long series (1979-1993) of very long baseline interferometry (VLBI) estimates of nutation angles. Secular rates of change of the nutation angles to represent corrections to the precession constant and a secular change of the obliquity of the ecliptic are included in the theory. Time dependent amplitudes of the Free Core Nutation (FCN) that is most likely excited by variations in atmospheric pressure are included when the geophysical parameters are estimated. The complex components of the prograde annual nutation are estimated simultaneously with the geophysical parameters because of the large contribution to the nutation from the S1 atmospheric tide. The weighted root mean square (WRMS) scatter of the nutation angle estimates about this new model are 0.32 mas and the largest correction to the series when the amplitudes of the ten largest nutations are estimated is 0.17 ± 0.03 mas for the in phase component of the prograde 18.6 year nutation.

In this paper I combine the results of a set of population synthesis models with simple Montecarlo simulations of stochastic effects in the number of stars occupying sparsely populated stellar evolutionary phases, to show that the scatter observed in the magnitudes and colors of LMC and NGC 7252 star clusters can be understood in the framework of current stellar evolution theory, without the need to introduce ad-hoc corrections (e.g. artificially increasing the number of AGB stars).