From prestellar cores to solar nebulae

Understanding the formation of stars and the formation of planets, are both cornerstone challenges in modern astronomy. These highly multi-physics and multi-scale problems are tightly linked through the formation and evolution of proto-planetary discs. As such, they should ideally be apprehended simultaneously. In practice however, due to the great variety of instruments and techniques that must be used as well as the profusion and complexity of physical processes, the field is traditionally subdivided in several communities addressing specific questions all relevant to reach a global understanding, including (i) the formation, collapse and fragmentation of dense cores which also addresses the issue of centrifugally supported discs formation and early evolution around the youngest protostars, (ii) the late evolution of protoplanetary discs whose main objectives are the origin of the angular momentum transportation, the dynamics of gas and dust as well as the growth from grains to planetesimals, (iii) the study of solar nebulae constituents such as grains and meteorites from a dynamical and chemical perspectives.

Recent facilities such as the space observatory Herschel, the interferometer ALMA, the SPHERE instrument on the VLT, and the forthcoming SPIROU camera and James Webb Space Telescope have already or ought to revolutionize the field of star and planet formation. These new observational tools, as well as the development of comprehensive models and numerical simulations including more and more physical ingredients, finally open the door to meaningful combination of tools and results from the different communities. Such a meeting would be very timely because of the imminent need to establish cross-disciplinary collaborations transcending the historical divisions, so as to identify cornerstone questions and use these new tools at the best of their constraining power, to ultimately compare, combine, and synthesize knowledge of the end-to-end process of star and planet formation.

The present program aims at triggering progress on these various questions, by bringing together worldwide experts performing observational and theoretical work, covering both the dynamical and micro-physical processes. In particular it aims at strengthening the links between the various specialized scientific communities. In this context, numerous questions remain to be addressed.

A Ψ2 program at
Institut d'Astrophysique Spatiale in Orsay, France

The Ψ2 programs bring scientists in a single location for a signficant amount of time. Unlike typical conferences, the daily schedule is composed of informal talks in the morning and open time for discussion and collaborative work in the rest of the day.

In this Ψ2 program we aim to bring together pioneering researchers to pose, explore, and answer paramount questions about the evolution from prestellar cores to solar nebulae. The participants will be selected in order to foster exploration in observations, data combination, synthesis with numerical simulations, laboratory work, and theory.

The program will highlight the three following topics, one per two weeks.

Formation, collapse and fragmentation of dense cores

  • What is the intensity and the structure of magnetic field in cores and discs?
  • What are the influences of the various snow lines on the protostellar phase
  • When do discs form ?
  • What is their initial size distribution ?

Evolution of protoplanetary discs

  • How do they grow and evolve during the main accretion phase ?
  • Are protostellar discs surrounding solar-type precursors massive enough to fragment ?
  • What role are playing ejection mechanisms in this process ?
  • Do they carry away a significant fraction of angular momentum ?
  • Do they produce high energy particles contributing to the ionization fraction at disc scales ?
  • Do they play a significant role in bringing some species to the gas phase by shocks and sputtering processes ?

The solar nebulae constituents

  • Can we use the cosmo-chemical abundances to constrain the mixing between interstellar medium and the proto-solar molecular clouds?
  • When and where are the sources for the extinct radio activities being produced and how do they get mixed and transported from their nucleosynthetic source to the first solids in the disc?
  • What are the influence of the extinct radioactivity’s on planetesimal formation / chronology?


The goal is to put together a sufficiently large number of observers, experimentalists and theoreticians for a significant amount of time in order to provoke a real exchange between these communities. By confronting a large number of viewpoints / constraints, this extensive work in common will enable specific aspects to emerge. This collaborative work should also lead to the identification of new observational probes that could be used to test some aspects of the protostellar cores to disk evolution.

Participants will be selected in order to foster interaction between these different communities.


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(deadline: 31th December 2017, limited number of places)