Abstract

The classical and simplistic (but to some extent correct) view of star and planet formation describes the gravitational collapse of an isolated core, followed by the coexistence of an envelope and disk structure. Since the emergence of a protoplanetary disk occurs quasi simultaneously with that of the star, it could be expected that the star would dominate the orientation of the spin axis of the system so that stars, disks and planets would display coplanar configurations. However, evidence on misalignments between the inner and outer disk components have been reported in several cases, as well as significant mutual inclinations among planets and recently among stars and debris disks. Mechanisms invoked to explain this departure from coplanarity and their relation to disk and planet formation have been recently grouped onto three categories: primordial, post planet formation and independent of the planet formation process. Each of these kinds of mechanisms have predictions that operate a different time scales and system properties. In this pilot study we compiled a sample of protoplanetary disk systems with large cavities (so called transition disks) and show that no individual mechanism can explain the mutual inclinations found between disks (and subparts of them) and their host stars at this evolutionary stage.

Abstract

Hubble observations of massive young clusters in the Magellanic Clouds and Milky Way have revolutionised our understanding of low-mass star formation in these environments, revealing several thousands of new pre-main sequence (PMS) stars. These objects are still undergoing active mass accretion, as witnessed by excess emission in the Halpha band. This is presently the largest and most homogeneous sample of PMS objects, on which we are conducting the first comprehensive and systematic study of the PMS phase. By spanning a wide range of masses (0.5-4 Msun), metallicities (0.1-1 Zsun) and ages (0.5-30 Myr), we probe a parameter space covering the bulk of all stars that form in the Universe. Our observations consistently suggest that in low-metallicity environments PMS stars accrete at higher rates and for longer times than in the solar neighbourhood. Spectra recently obtained with JWST/NIRSpec fully confirm this picture, revealing for the first time spectroscopically-derived mass accretion rates of about 1E-8 Msolar/year for PMS stars with ages in the range 20-30 Myr. JWST spectroscopy and photometry also reveal NIR excess from these stars, clearly showing that circumstellar discs are still surrounding these objects, providing more time for planets to form and grow than in the Milky Way. The spectra also reveal prominent H2 ro-vibrational lines, witnessing molecular winds associated with shocks and/or photodissociation phenomena in the circumstellar discs. No such features are seen in the spectra of main- sequence stars. This further confirms that discs are present around even the oldest of these PMS stars. In these low-metallicity environments (similar to those at high redshift) planet formation is likely different from what we currently know.

Abstract

The processes regulating star formation in galaxies act across many orders of magnitude in spatial scale. Thus, a key challenge in understanding star formation is bridging the small-scale physics within molecular clouds and the large-scale structure of spiral galaxies. Fully constraining the physics of star formation across these scales requires constraints on both the 3D spatial structure and dynamical state of the interstellar medium (ISM), the combination of which has been an essentially unknown quantity in the field of star formation research. In this talk, I will discuss ongoing efforts to construct high-dimensional models of the ISM in the solar neighborhood by combining data science and visualization techniques with wide-field photometric, astrometric, and spectroscopic surveys. On kiloparsec scales, I will discuss how “3D dust mapping” has enabled constraints on the global distribution of molecular clouds, revealing new links between clouds long thought to be isolated and challenging fundamental assumptions about the shape and position of a nearby spiral arm. On parsec scales, I will show how combining 3D dust mapping with the 3D space motions of young stars can explain the origin of all local star formation as being driven by the expansion of the Local Bubble, the nearest superbubble to the Sun. Finally, on au-scales, I will discuss the implications that the Sun’s trajectory through the ISM has for the properties of the heliosphere and the geological record here on Earth. I will conclude by previewing the opportunities enabled by future infrared surveys, including SDSS-V and Roman, which together will pave the way for a unified understanding of the multi-scale physical processes shaping star formation in diverse environments across the Milky Way’s disk.

Abstract

What is the impact of stellar multiplicity on planet formation? This question is motivated by the fact that the process of star formation naturally leads to a very high fraction of stellar multiplicity. What is more, planet formation occurs early on around young stellar objects. The conclusion that follows is unavoidable: planetary cradles (a.k.a protoplanetary discs) are deeply affected by the presence of nearby stars. In this talk we will explore disc dynamics and planet evolution around binary and triple stellar systems, as opposed to single stars. First, I will briefly review the recent theoretical works on this subject. This will be illustrated with some representative examples of observed multiple stellar systems with discs and planets (e.g. ALMA, VLT/SPHERE). Then, I will present our modelling efforts on protoplanetary discs dynamics in the presence of several stars. Finally, based on this comprehensive picture, we will discuss the current open questions regarding planet formation in multiple stellar systems.

Abstract

Young stars accrete material from their surrounding protoplanetary disks. Simulations predict that matter accretes via the stellar magnetic field lines, leaving a hot spot with a density gradient. We present observational evidence of this density gradient utilizing a comprehensive, coordinated multi-epoch multi-wavelength observing campaign of the T Tauri star GM Aur. UV and optical light curves of GM Aur display periodicity, but do not peak at the same time. The offset peaks are due to a hot spot with a density gradient; different density regions of the hot spot emit at distinct wavelengths and have separate physical locations leading to periodic, offset peaks in the UV and optical as the hot spot rotates along with the star. These observations confirm theoretical predictions and demonstrate the insights gained from coordinated multiepoch multiwavelength observations.

Abstract

The last 25 years have seen transformational advances in our knowledge of planetary demographics, together with equally impressive and ongoing improvements in the imaging and characterization of protoplanetary disks. Fortunately, there remains plenty for observers, theorists, and experimenters to do. One of the basic questions raised by the first exoplanet discoveries - what is the nature and role of migration in forming planetary systems - remains largely open. New theoretical processes, including the streaming instability and pebble accretion, have been identified but remain imperfectly understood. And frontier observational areas, such as the discovery of circumplanetary disks, have emerged. I will discuss these problems, with a focus both on what remains unknown and on our ongoing work to develop new computational methods to tackle them.

Abstract

This talk will present some highlights by our group of recent ALMA observations of molecules in star-forming regions, from the earliest pre-stellar cores to planet-forming disks.  Thanks to ALMA, the chemistry of water and more complex molecules can now be traced through the various evolutionary stages on solar system scales.  Why are some sources rich in complex molecules and others not?  What is the relation to the fascinating structures seen in disks? Implications for the material (e.g., C/O) out of which planets are built will be discussed and prospects for JWST (coming soon!) will be highlighted. Overall, the data point to formation of many species in the earliest phases that are then largely inherited in disks. Dust traps play a key role in the redistribution of material to the planet-building zones.

Abstract

In this talk, I will review the status of infrared spectroscopy of molecules in planet-forming (Class II) disks from 20 years data from ground- and space-based observatories. I will present a new database of infrared (2.7-35 um) spectra from VLT-CRIRES, IRTF-iSHELL, Keck-NIRSPEC, VLT-VISIR, Spitzer-IRS that is now available to the community in support of new observing and modeling efforts worldwide. I will discuss multiple science angles from studying different kinematic components that trace gas in inner disk rings and winds at 0.01-10 au: their physical and chemical structure, kinematics, excitation, and evolution. I will conclude by demonstrating how the synergy of data from multiple instruments will be necessary in the era of JWST observations, in the context of the spectral range, molecular tracers, and resolving power that each instrument offers.

Abstract

Reconstructing the morphology of the Milky Way from our vantage point is a complicated task. Star clusters have been used as a convenient tracer of the Galactic structure for almost a century. Their ages and distances are easier to estimate than for most other astronomical objects. The ongoing ESA Gaia mission is transforming our understanding of the Milky Way structure and history by providing astrometric data of unprecedented precision. The amount of new data and the high dimensionality of the catalogues require new approaches for data analysis. In this new paradigm, star clusters are still relevant objects of interest. During this talk I will review some results enabled by Gaia DR2 and EDR3 in the discovery and characterisation of clusters, and what these findings tell us about the present state of the Milky Way and its evolutionary history.

Abstract

The formation and evolution of planets is intimately related to the physical conditions, the evolution and the dispersal of their natal planet forming disc. In this talk I will briefly summarise the basics behind photoevaporation models of disc dispersal, emphasising some of their expected influence on planet formation and migration. I will also focus on the predictive aspects of these models and how well they compare with current observations.

Abstract

On Christmas Day, the James Webb Space Telescope was launched from Kourou and is currently undergoing deployment on its way to L2. After presenting a status update and general timeline of what to expect over the next few months, I will introduce the four main instruments and describe what they can do to help us understand young stars and their outflows. There will be a particular emphasis on the Mid-Infrared Instrument (MIRI), which my institute help build, and its use in observing highly embedded protostars. Finally, I will outline what is planned in star formation studies within the Guaranteed Time Observing (GTO) programme.

Abstract

In this talk I will review recent advances in our understanding of the launching mechanism of protostellar jets and outflows and how these processes may impact proto-planetary disk physics and evolution. I will first show current constraints on jet launching derived from high-angular resolution observations of the jet base. I will then present results obtained with ALMA on the base of low-velocity molecular outflows that challenge their traditional interpretation as entrained matter. I will discuss the recent progress and challenges brought by these new observations in trying to understand the role played by disk winds in the transport of mass and angular momentum in proto-planetary disks. Finally I will outline the prospects brought by future observatories like JWST to solve some of the remaining one questions.

Abstract

Since the ’80s the Einstein observatory has shown that the Young Stellar Objects (YSOs), across most of their evolutive phases, emit X-rays with luminosities up to 103–104 times than old late-type stars (like the Sun) and that the X-ray emission is highly variable. This was an unexpected discovery that thanks to the transformational capabilities of the Chandra and XMM-Newton observatories has made X-ray observations a powerful tool, together with other wavelength data, to study both the complex physics at work in the YSOs and to trace and characterize the star formation process up to distance of a few kpc around the Sun. 

I will summarize some of the results obtained and how they have influenced our current understanding of physical processes at work and I will discuss some of the still open issues.

Abstract

In this talk I will discuss our understanding of disk bulk properties and their evolution at the time of planet formation. I will critically revisit our current understanding of disk masses and discuss the evidence for disk-planet interaction, suggesting that planet formation occurs very early in the disk lifetime and significantly affects the evolution of the (observed) disk properties. I will discuss the recent progress and challenges in trying to constrain the initial disk properties. I will also discuss some of the hints that the common framework of viscously evolving disks may show discrepancies with the observed trends, and how we can try to design tests to constrain the importance of winds in disk evolution.