Massive stars are essentially the driving force of the entire universe – in terms of energy, momentum, and baryonic cycling through galaxies – over cosmic time. Without them, the present universe would simply not exist.
Despite their importance and the remarkable progress made by the Astrophysical community in understanding their physical properties and the interconnected processes that drive their end-to-end life cycle, many critical questions remain open. This is a consequence of their complex formation process and subsequent evolution. In brief, the whole end-to-end life-cycle of these extreme stellar objects is known to be dominated by (1) their initial mass, which is intimately linked to the star formation process, (2) the large amount of angular momentum remaining in the star once it has reached the Zero Age Main Sequence, and how this is shared between their cores and surfaces along their evolution, (3) mass transfer processes occurring in the high percentage of stars of this type born in binary and multiple systems, and (4) the strong -- sometimes steady, sometimes eruptive – mass loss events driven by the interaction between the stellar radiation and the outer layers of these stars. Overall, this leads to a still not fully understood diversity of possible final fates (represented by a variety of core-collapse supernovae events) and end products (including isolated neutron stars and black holes, and binary systems comprising two of these stellar corpses, which can eventually lead to a gravitational wave event if they merge).
Ensuring advance in this field hence requires the work and close interaction of researchers covering different domains of expertise, including stellar atmosphere modelling, stellar structure and evolution modelling, quantitative spectroscopy in different spectral windows and different stages of evolution, as well as the investigation (both observationally and from the modelling point of view) of the star formation process and the connection between massive stellar evolution and the associated end-products.
This MIAPbP program has been designed to create a stimulating environment that fosters interdisciplinary discussions spanning theoretical, observational, and modelling aspects of massive star formation, evolution, and stellar atmospheres/winds. The program is structured into four broad Topical Blocks (TB) over four weeks:
TB-1: Mass – TB-2: Angular Momentum – TB-3: Winds – TB-4: Stellar and Cluster Dynamics
Our goal is to encourage cross-domain collaborations between experts from diverse disciplines, including spectroscopy and photometry, stellar atmosphere and evolution modelling, asteroseismology, and star formation studies, helping to advance the overarching challenge of integrating our understanding of massive star formation, evolution, and their end products into a coherent picture valid across cosmic time.
Important note: For a better organization of the program, the final order of the topical blocks will be decided after the registration deadline, taking into account the availability of the registered participants
TB-1: Mass
This block will address the determination of spectroscopic, evolutionary, and dynamical masses, and how these feed into building the initial mass function (IMF). Discussions will include the effects of mass changes due to winds or binary mass transfer, and the links between stellar mass and the final fate of massive stars.
TB-2: Angular Momentum
Rotation plays a central role in the structure and evolution of massive stars. This block will focus on initial conditions, internal angular momentum transport, and how the angular-momentum budget evolves through processes such as mass transfer or winds. Special emphasis will be placed on the connections between rotation, surface abundances, and mixing processes.
TB-3: Winds
Massive stars lose a significant fraction of their mass through winds. This block will explore the launching mechanisms and characteristics of stellar winds, including steady, variable, and eruptive mass-loss episodes, wind clumping, and colliding winds. The broader consequences for stellar feedback, both on the end products of stellar evolution and on the surrounding interstellar medium (ISM), will also be discussed.
TB-4: Stellar and Cluster Dynamics
Massive stars rarely evolve in isolation. This block will focus on the dynamical and environmental contexts of massive star evolution, including the role of clusters, associations, and the field, as well as the formation of runaway stars. The links to explosive outcomes and compact remnants, supernovae, black holes, neutron stars, and gravitational wave sources, will form part of the discussions.
Some key scientific questions expected to be addressed by the MIAPbP program:
1. Technical Challenges in Stellar Observation: Among others, how can we extract basic information reliably – such as stellar masses, surface abundances, or wind properties – from UV, optical, and IR spectroscopy of massive stars, both single and binary, using modern stellar atmosphere models; or how can we interpret (sub)mm radio observations to accurately determine the masses of proto-stellar cores.
2. Stellar winds: Of particular relevance is the intense debate the community has had in the last decades about how we can obtain a reliable empirical characterization of steady/variable/eruptive mass loss events (including the impact of wind clumping), and how we can use this information to better understand which are the main launching mechanisms of these mass loss events along massive star evolution.
3. Star Formation Processes: A key longstanding question is how star-forming regions fragment on the smallest scales. The competing models – core accretion vs. turbulent core fragmentation – directly influence the initial mass function (IMF). Also, we still lack a comprehensive understanding of the kinematics of star-forming regions, including, e.g., how mass flows within molecular clouds, how this imparts momentum to the dense hub regions where we expect the clusters/massive stars to form, or how turbulence and magnetic fields regulate star formation at these scales. Additionally, the impact of environmental conditions on star formation outcomes, including the dynamics of young massive clusters, remains elusive.
4. Evolutionary Processes and Final Outcomes: We still lack a definitive, observationally confirmed, understanding of how initial conditions and key processes, such as internal angular momentum transfer, internal mixing, mass loss, and mass transfer in binary systems, influence the entire lifecycle of massive stars. Importantly, all these processes affect the properties and relative occurrence of their end-products – including supernovae, black holes, neutron stars, and gravitational wave events – as well as their feedback into the interstellar medium through ionizing radiation and mechanical energy.