Astrobiology emerged as a scientific discipline in Kazakhstan more than half-a-century ago and flourished for many years under the leadership of Gavriil A. Tikhov, the oldest Pulkovian astrophysicist, member of the Academy of Sciences of the KazSSR (ASKSSR), and corresponding member of the Academy of Sciences of the USSR.

Jean Heidmann (1923-2000) began his research career as a radio-astronomer in 1959 at Paris Observatory, investigating the structure of galaxies and the distance scale in the nearby universe. In the early 1980's, his scientific interest broadened to the search for extraterrestrial intelligence and he became a strong advocate of SETI, either from the ground or from space.

Trained as a physicist, George W. Wetherill (1925-2006) made seminal contributions to the fields of geochemical dating, meteoritical and asteroidal science, and the theory of the formation of terrestrial planets, evolving along the way into one of the first astrobiologists.

In recent years our knowledge of star, brown dwarf and planet formation has progressed immensely due to new data in the IR domain (Spitzer telescope), new X-ray campaigns such as the Chandra Orion Ultradeep Project (COUP) and the X-ray Emission Survey of Taurus (XEST), with XMM-Newton, as well as adaptive optics results and synoptic studies of young stellar and substellar objects.

It is now well established that young brown dwarfs harbor accretion disks –and thus undergo a T Tauri phase– similar to their low-mass stellar counterparts. The supporting evidence includes infrared and millimeter observations of the dust component as well as optical and infrared spectra with signatures of gas accretion and outflow. Recent findings suggest that disks are common even around young planetary mass objects. The ubiquity of circum-sub-stellar disks not only hints at a common formation scenario for PMOs, brown dwarfs and stars, but also offers a new regime for investigating processes such as episodic accretion, grain growth and disk clearing.

We present data from our ice mapping program IMAPE on the AKARI satellite. Initial results show a correlation between the abundance of CO2(s) and H2O(s), consistent with previous studies. We can trace abundances of molecules across a core using a single observation.

Unbiased, flux-limited surveys of protoplanetary disks and their parent stars currently exist for only a few clouds, primarily Taurus and IC 348, selected primarily by optical and near-IR data. Such surveys are essential to address questions of disk evolution as a function of stellar parameters such as spectral type, age, accretion activity and environment. Using the ‘Cores to Disks’ (c2d) Spitzer Legacy Program, we discovered a new population of young stellar objects (YSOs) in a region of only 0.8 deg2 in the Serpens Molecular Cloud. This sample contains 150 mid-IR bright (≥ 3 mJy at 8 μm) YSOs with infrared excess, having a broad range of SED types and luminosities. Serpens is therefore a unique target region for obtaining a complete, well-defined sample of multi-wavelength observations of young stars in a possible evolutionary sequence. Compared with other clouds such as Taurus and Chamaeleon, Serpens has an exceptionally high star-formation rate (5.7 × 10−5 M⊙ yr−1). Follow-up complimentary observations in the optical, near- and mid-infrared (Spitzer/IRS GO3) have allowed us to characterize both the central stars and the surrounding disks. The shape and slope of the mid-infrared excess provide information on the flaring geometry of the disks. The spectral features give constraints on grain growth and mineralogy, which in turn probes heating and radial mixing. The presence of PAH features traces UV radiation, whereas Hα and Brγ are used as diagnostics of accretion. Assuming that all stars within a sufficiently small region are nearly coeval, this provides direct constraints on the importance of environment and initial conditions on disk evolution. In this meeting, we have presented our latest results on this rich populations of YSOs, as detailed in Oliveira et al. (2009, 2010). We have discussed connections between the evolution of the disks and that of their harboring stars, and the processes that determine the evolutionary sequence of protoplanetary disks.

I review recent studies of transitional protoplanetary disks, in which the planet forming regions are being cleared of material. The dust and accretion characteristics of these objects as a function of their environment and host star age and mass reveal important clues as to how disk structure is modified and ultimately destroyed. Clearing mechanisms such as grain growth, dynamical interactions with embedded planets or stellar companions, and photoevaporation are likely all involved, pointing to diverse disk evolutionary paths.

In Morales et al. (2009), we have recently investigated the mid-infrared (3.6 to 8.0 micron) variability of young-stellar objects (YSOs) using the IRAC camera on the Spitzer Space Telescope. Specifically, we obtained synoptic photometry of about 70 YSOs in the ~1 Myr old IC1396A globule over a 14 day period. More than half of the YSOs were detectably variable, with amplitudes up to about 0.2 magnitudes. About a third of these objects showed quasi-sinusoidal light curves with apparent periods of typically 5 to 12 days. At least two families of models can explain such light curves: (a) a Class II YSO with a photospheric hot spot which locally heats the inner circumstellar disk which is viewed from slightly above the disk plane, and (b) a YSO with a warped disk or with some other non-axisymmetric inner disk density profile, also seen with a view angle slightly above the disk plane. The two models can both yield light curve shapes and amplitudes similar to what we observe in the mid-infrared, but produce very different light curves at shorter wavelengths dominated by the stellar photosphere. Because we only had IRAC photometry for IC1396A, we were not able to discriminate between the two models for this set of data.

The Corot satellite observed the young stellar cluster NGC 2264 during 23 days in March 2008. This was the first time a group of young accreting stars, classical T Tauri stars (CTTS), were followed ininterruptedly with high photometric accuracy for such a long run. Before the Corot observations, AA Tau (Bouvier et al. 2003, A&A, 409, 169 and Bouvier et al. 2007, A&A, 463, 1017) was one of the few CTTS systems that had been analysed synoptically over several consecutive rotational periods. Its analysis suggested a highly dynamical star-disk interaction mediated by the stellar magnetic field, as predicted by magneto-hydrodynamical simulations of young accreting systems.

In this review I gave an overview of the structure and evolution of protoplanetary disks, and how the evolution of dust affects this. This is an important topic because these determine the conditions under which planets are formed, or were formed in our solar system 4.5 billion years ago.

Using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) we observed several proto-planetary disks in the dust continuum emission at 1.3 and 2.8 mm (Isella et al. 2009a, 2009b). The observations have angular resolution between 0.15 and 0.7 arcsecond, corresponding to spatial scales spanning from about the orbit of Saturn up to about the orbital radius of Pluto. The observed disks are characterized by a variety of radial profiles for the dust density. We observe inner disk clearing as well as smooth density profiles, suggesting that disks may form, or evolve, in different ways. Despite that, we find that the characteristic disk radius is correlated with the stellar age increasing from 20 AU to 100 AU over about 5 Myr. Interpreting our results in terms of the temporal evolution of a viscous α-disk, we estimate that (i) at the beginning of the disk evolution about 60% of the circumstellar material was located inside radii of 25-40 AU, (ii) that disks formed with masses from 0.05 to 0.4 solar masses and (iii) that the viscous timescale at the disk initial radius is about 0.1-0.3 Myr. Viscous disk models tightly link the surface density Σ(R) with the radial profile of the disk viscosity ν(R)∝ Rγ. We find values of γ ranging from -0.8 to 0.8, suggesting that the viscosity dependence on the orbital radius can be very different in the observed disks. We demonstrate that the similarity solution for the surface density for γ < 0 can explain the properties of some “transitional” disks without requiring discontinuities in the disk surface density. In the case of LkCa 15, a smooth distribution of material from few stellar radii to about 240 AU can produce both the observed SED and the spatially resolved continuum emission at millimeter wavelengths. For two sources, RY Tau and DG Tau, we observed the dust emission with a resolution as high as 0.15 arcsecond, which corresponds to a spatial scale of 20 AU at the distance of the two stars. The achieved angular resolution is a factor 2 higher than any existing observation of circumstellar disks at the same wavelengths and enable us to investigate the disk structure with unprecedent details. In particular, we present a first attempt to derive the radial profile of the slope of the dust opacity β. We find mean values of β of 0.5 and 0.7 for DG Tau and RY Tau respectively and we exclude that β may vary by more than ±0.4 between 20-70 AU. This implies that the circumstellar dust has a maximum grain size between 10 μm and few centimeters.

The timescale over which gas-rich disks disperse profoundly affects not only the formation of giant planets but also the habitability of terrestrial planets. In this contributed talk we presented new atomic and molecular diagnostics that can be used to trace the dispersal of gas at disk radii where planets form. We also showed the first observational evidence for photoevaporation driven by the central star and discussed the efficiency of this disk dispersal mechanism.

Several lines of evidence suggest that planet formation may be well underway within the circumstellar disk of the enigmatic Herbig Be star HD100546, including a cleared inner cavity, spiral structure, and similar dust mineralogy as seen in our own solar system. To learn more about the processes occurring in this disk we have conducted a multi-frequency observing program with the Australia Telescope Compact Array (ATCA).

High-energy radiation and particles profoundly affect circumstellar disk gas and solids. We discuss stellar high-energy sources and summarize their effects on circumstellar disks.

The physics of protoplanetary disks and the early stages of planet formation is strongly affected by the level of ionization of the largely-neutral gas (Armitage 2009; Balbus 2009). Where the ionization fraction is above some limit around ~ 10−12, the magnetorotational instability (MRI) will ensue and the gas will become turbulent. The presence or absence of disk turbulence at various locations and times has profound implications for viscosity, accretion, dust settling, protoplanet migration and other physical processes. The dominant source of ionization is very likely X-rays from the host star (Glassgold et al. 2000). X-ray emission is elevated in all pre-main sequence stars primarily due to the magnetic reconnection flares similar to, but much more powerful and frequent than, flares on the surface of the contemporary Sun (Feigelson et al. 2007).

Circumstellar disks are mostly made of gas. Constraining the spatial and thermal structure of the gas, and its time evolution, is crucial to understand the star- and planet-formation processes. Models predict that the gas is affected by UV and X-ray radiation from the central young stellar object (YSO), but many uncertainties remain, e.g. whether the EUV emission actually reaches the disk or is absorbed by disk winds. The infrared [Ne II] and [Ne III] fine structure lines at 12.81μm and 15.55μm have been theoretically predicted to trace the circumstellar disk gas subject to X-ray heating and ionization.

The early solar system represents the only case we have of a circumstellar disk that can be investigated “in situ” -albeit 4.6 Gyr after its formation. Meteorites studies give mounting evidence for an intense irradiation phase of the young circumsolar disk by energetic particles, and also for contamination by products of high-mass stellar and/or explosive nucleosynthesis. We thus discuss the conditions of the birth of the solar system in a high-mass star environment.

Jets are found in a wide range of accreting young stars, from brown dwarfs to massive protostars, but their launch region(s) and their role in angular momentum extraction are still debated. Many observational constraints exist on jet properties, including jet widths, kinematics along and across the jet, possible rotation signatures, ejection/accretion ratio, depletion and molecular counterparts. This contribution compares popular models, in particular disk winds, with these constraints and with MHD numerical simulations, highlighting a few open issues.

Around high-mass Young Stellar Objects (YSOs), outflows are expected to be launched and collimated by accretion disks inside radii of 100 AU. Strong observational constraints on disk-mediated accretion in this context have been scarce, largely owing to difficulties in probing the circumstellar gas at scales 10-100 AU around high-mass YSOs, which are on average distant (>1 Kpc), form in clusters, and ignite quickly whilst still enshrouded in dusty envelopes. Radio Source I in Orion BN/KL is the nearest example of a high-mass YSO, and only one of three YSOs known to power SiO masers. Using VLA and VLBA observations of different SiO maser transitions, the KaLYPSO project (http://www.cfa.harvard.edu/kalypso/) aims to overcome past observational limitations by mapping the structure, 3-D velocity field, and dynamical evolution of the circumstellar gas within 1000 AU from Source I. Based on 19 epochs of VLBA observations of v=1,2 SiO masers over ~2 years, we produced a movie of bulk gas flow tracing the compact disk and the base of the protostellar wind at radii < 100 AU from Source I. In addition, we have used the VLA to map 7mm SiO v=0 emission and track proper motions over 10 years. We identify a narrowly collimated outflow with a mean motion of 18 km/s at radii 100-1000 AU, along a NE-SW axis perpendicular to that of the disk traced by the v=1,2 masers. The VLBA and VLA data exclude alternate models that place outflow from Source I along a NW-SE axis. The analysis of the complete (VLBA and VLA) dataset provides the most detailed evidence to date that high-mass star formation occurs via disk-mediated accretion.