The motion of P/Borrelly has been investigated using all precise published positions and taking into account the perturbations by Venus to Pluto. Nongravitational forces have been found to influence the motion of the comet considerably, formerly as a secular deceleration, more recently as a secular acceleration. By linking the seven apparitions 1904–1960, with allowance for the nongravitational effects, we have obtained a set of elements which represents 802 observations with a mean error of 1′.89.

Japanese group is promoting infrared space astrometry missions, JASMINE project series, in international collaboration with Gaia DPAC team. In this paper, the outline of Nano-JASMINE and Small-JASMINE missions is shown.

Oscillations in white dwarfs of hydrogen or helium envelopes are believed to be excited close to the surface, where convective energy transport dominates the stellar luminosity. The convective motion in these stars is fast and can respond instantaneously to the pulsation state. In this limit, we find the convective envelope to be the seat of mode excitation because it acts as an insulating blanket with respect to the perturbed flux that enters it from below. This retaining of the flux leads to driving. Driving exceeds radiative damping provided ωτc ≥ 1, where ω is the radian frequency of the mode and τc ≈ 4τth with τth being the thermal time constant evaluated at the base of the convective envelope. We follow Brickhill (1991) in naming this mechanism as ‘convective driving’. We also studied the dynamical interaction between turbulent convection and pulsation. In the limit of fast convection, turbulent damping inside the convective region is negligible, while that coming from the overshoot region is more significant. I discuss the application of ‘convective driving’ in other types of pulsating stars.

Investigators generally conjecture a steady flux of new comets from the Oort cloud through the inner Solar system. Due to gravitational perturbations by major planets these objects may escape, become long period comets (LPCs) if their orbital periods P are larger than 200yr or become short period comets (SPCs) when their period is less than 200yr. SPCs are further divided in two types: the Halley type comets (HT, for P > 20yr) and the Jupiter family comets (JF, for P < 20yr).

During the 25 years that the author has been involved in astrometry, the quality of ground-based parallaxes has increased by about a factor of 10 (from 3 mas to 0.3 mas), but the quantity has increased by only a few hundred. When asked, the average astronomer will cite the $H^2$ space missions (Hubble and Hipparcos) as the great advances in astrometry even thought the ground-based work has played a critical role in the understanding classes of stars such as the L- and T-dwarfs. The next decade promises stunning advances in both the quality and quantity of parallax measurements, and both ground- and space-based projects will play significant roles. The Gaia space mission and the various ground-based telescopes with large etendue (DMT, LSST, Pan-STARRS, etc.) will improve the quality or quantity (or both) by factors of a thousand or more. The situation will be discussed, and the author will express his hope that he might live long enough to see the fruits of these labors.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We review the nearby debris disk structures revealed by multi-wavelength images from Spitzer and Herschel, and complemented with detailed spectral energy distribution modeling. Similar to the definition of habitable zones around stars, debris disk structures should be identified and characterized in terms of dust temperatures rather than physical distances so that the heating power of different spectral type of stars is taken into account and common features in disks can be discussed and compared directly. Common features, such as warm (~150 K) dust belts near the water-ice line and cold (~50 K) Kuiper-belt analogs, give rise to our emerging understanding of the levels of order in debris disk structures and illuminate various processes about the formation and evolution of exoplanetary systems. In light of the disk structures in the debris disk twins (Vega and Fomalhaut), and the current limits on the masses of planetary objects, we suggest that the large gap between the warm and cold dust belts is the best signpost for multiple (low-mass) planets beyond the water-ice line.

In 1975 a remarkably large number of short-period comets were discovered - only the most recent number from 1977 is comparable. While the average discovery rate has been 0.8-1.0 new short-period comets per year (Kresák 1974), in 1975 there were six discoveries. In five of the cases IAU Circulars soon afterwards contained indications that close encounters with Jupiter had recently taken place (Marsden 1975, Kastel' 1975). For two of the comets, P/Kohoutek and P/Smirnova-Chernykh, also pre-encounter orbital elements were outlined, suggesting that substantial reductions of the perihelion distances had occurred.

We discuss a newly-developed technique for spatially resolving starspots on some of the more rapidly rotating RS CVn stars. Basically, the method uses high resolution, very high signal-to-noise spectral line profiles and exploits the Doppler velocity correspondence between position across the stellar disk and wavelength position across a rotationally broadened line profile to synthesize an image of the star, showing the location, sizes, and shapes of its starspots. Though still in a developmental stage, the technique is already yielding information about the structure and general appearance of starspots. Examples of Doppler Imaging observations of HR 1099 will be presented, along with a movie showing the behavior of synthetic line profiles generated from a computer spot model.

The Maya 2012 prophecy foretells events that will occur at the close of the current Maya ‘era’ and at the end of the 13th BˈAKTUN period of the Maya calendar. This paper explores the mythic and astronomical events that occurred previously at the start of the Maya era in 3114 BC corresponding to the close of the first 13-BˈAKTUN period. These two 13-BˈAKTUN Period Endings, separated by a span of approximately 5125 years, are like two bookends on a single shelf that inextricably link ancient Maya conceptions of time, mythic history and prophecy. The following presentation will demonstrate how in this case, the past is very much prologue. Mythic events and godly actions recorded at the beginning of the era directly parallel those actions that will occur at the end of the era. In addition, new insights will be shared into how ancient Maya scribes linked Era Day events to temple dedications and architecture to reflect the sun's daily solar trek—a journey charted and revered by ancient peoples from all corners of the Americas.

We found that in regions of high mass star formation the CS emission correlates well with the dust continuum emission and is therefore a good tracer of the total mass while the N$_2$H$^+$ distribution is frequently very different. This is opposite to their typical behavior in low-mass cores. The behavior of other high density tracers varies from source to source but most of them are closer to CS. Radial density profiles in massive cores are fitted by power laws with indices about −1.6, as derived from the dust continuum emission. The radial temperature dependence on intermediate scales is close to the theoretically expected one for a centrally heated optically thin cloud. The velocity dispersion either remains constant or decreases from the core center to the edge. Several cores including those without known embedded IR sources show signs of infall motions. They can represent the earliest phases of massive protostars. There are implicit arguments in favor of small-scale clumpiness in the cores.

Inversion methods have been used successfully for the Sun. The stars with the next richest set of observed frequencies are the white dwarfs. We consider here the viability of numerical inversions for these stars. We find that, while the number of presently observed modes in the white dwarf GD 358 is too small for structural inversions, such inversions would be possible if the frequencies of all modes with 1 ≤ l ≤ 3 were observed. This is possible for space observations by e.g. Eddington.

Star-formation is one of the main processes that shape galaxies, and together with black-hole accretion activity the two agents of energy production in galaxies. It is important on a range of scales from star clusters/OB associations to galaxy-wide and even group/cluster scales. Recently, studies of star-formation in sub-galactic and galaxy-wide scales have met significant advances owing to: (a) developments in the theory of stellar evolution, stellar atmospheres, and radiative transfer in the interstellar medium; (b) the availability of more sensitive and higher resolution data; and (c) observations in previously poorly charted wavebands (e.g. Ultraviolet, Infrared, and X-rays). These data allow us to study more galaxies at ever-increasing distances and nearby galaxies in greater detail, and different modes of star formation activity such as massive star formation and low level continuous star formation in a variety of environments. In this contribution we summarize recent results in the fields of multi-wavelength calibrations of star-formation rate indicators, the Stellar Initial Mass function, and radiative transfer and modeling of the Spectrale Energy Disrtributions of galaxies.

Observing supernova remnants provides important clues to the nature of supernova explosions. Conversely, the late stages of stellar evolution and the mechanism of supernova explosions affect supernova remnants through circumstellar matter, stellar remnants, and nucleosynthesis. The elements of supernova classification and the connection between supernova type and remnant properties are explored. A special emphasis is placed on SN 1987a which provides a unique opportunity to learn the connection between the star that exploded (whose name we know) and the remnant that will develop in our lifetimes.

We present new and independent estimates of the distances to the Magellanic Clouds (MCs) using near-infrared (NIR) and optical–NIR period–Wesenheit (PW) relations. The slopes of the PW relations are, within the dispersion, linear over the entire period range and independent of metal content. The absolute zero points were fixed using Galactic Cepheids with distances based on the infrared surface-brightness method. The true distance modulus we found for the Large Magellanic Cloud—(m − M)0 = 18.48 ± 0.01 ± 0.10 mag—and the Small Magellanic Cloud—(m − M)0 = 18.94 ± 0.01 ± 0.10 mag—agree quite well with similar distance determinations based on robust distance indicators. We also briefly discuss the evolutionary and pulsation properties of MC Cepheids.

A study of the period–amplitude relation for RR Lyrae variables in the globular clusters 47 Tucanae, NGC 6441 and M55 confirms a recent finding that the period–amplitude relation for RRab stars with ‘normal’ light curves is not a function of metal abundance. Evolutionary effects are more important.

It has long been known that rotation can have an appreciable impact on stellar pulsation — by modifying the usual p and g modes found in the non-rotating case, and by introducing new classes of modes. However, it's only relatively recently that advances in numerical simulations and complementary theoretical treatments have enabled us to model these phenomena in any great detail. In this talk I'll review highlights in this area (the ‘Greatest Hits’), before considering the flip side (or the ‘B-side’, for those of us old enough to remember vinyl records) of the pulsation-rotation interaction: how pulsation can itself influence internal rotation profiles.

We analyse star cluster properties in the nearby spiral galaxy M33, combining our extensive HST WFPC2 photometry and ground-based follow up spectroscopy. These data show that cluster velocity dispersion increases with age. Simulations comparing synthetic disk and halo populations with observations indicate a composite disk/halo system for the old M33 clusters. The best fit fraction of 85 ± 5% halo plus 15 ± 5% disk differs from that found in the Milky Way, where ∼ 30% of the globular clusters are metal rich objects associated with the bulge and/or thick disk. Spectroscopic line indices for a halo subsample (17 objects) reveal an age spread of ∼ 5 — 7 Gyr, and little progression in metal abundance with age. This is consistent with a chaotic formation for a substantial portion of the M33 halo, and also consistent with an accretion origin for a large number of the halo clusters.

During the past three years the measurement of stellar radial velocities has formed an important part of the spectroscopic programme of most observatories possessing large telescopes. As observations are carried to fainter and fainter stars and the number of observable objects increases rapidly, a natural development has been the selection of special groups and types of stars, the radial velocities of which will aid in the solution of certain specific problems. Illustrations are the studies of the O, B and A type stars made at the Dominion Astrophysical, the Lick, and the Simeis Observatories, of the members of the galactic clusters at the Lick Observatory, and of the fainter Cepheid variables and early-type stars with strong interstellar lines at the Mount Wilson Observatory.

New determination of the Earth orientation parameters (EOP), based on optical astrometry observations since the beginning of the century, is now under preparation by the Working group established by Commission 19 of the IAU. The Hipparcos catalog is to define the celestial reference frame in which the new series of EOP are to be described. The novelties of the prepared solution are the higher resolution (5 days) and more parameters estimated from the solution (celestial pole offsets, rheological parameters of the Earth, certain instrumental constants). The mathematical model of the solution is described, and the results based on the observations made with 46 instruments at 29 observatories and a preliminary Hipparcos catalog are presented.

We discuss the difficulties of forming earth-like planets in metal-poor environments, such as those prevailing in the Galactic halo (Pop II), the Magellanic Clouds, and the early universe. We suggest that, with fewer heavy elements available, terrestrial planets will be smaller size and lower mass than in our solar system (solar metallicity). Such planets may not be able to sustain life as we know it. Therefore, the chances of very old lifeforms in the universe are slim, and a threshold metallicty (90% solar?) may exist for life to originate on large enough earth-like planets.