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Modeling and Observing
DEnse STellar systems




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    Most stars in most galaxies will never experience a collision or even a close encounter with another star. Typical collision time scales in the solar neighborhood of the Milky Way galaxy exceed the age of the universe by many orders of magnitude, so physical stellar interactions are extremely rare. However, in some parts of the universe -- in galactic nuclei and many star clusters -- circumstances have conspired to create conditions in which physical collisions between stars are commonplace events. Such dense stellar systems stand at the interface between stellar dynamics and stellar evolution. Often owing their existence to purely dynamical processes, these systems offer wholly new channels for stars to evolve, allowing the formation of stellar species completely inaccessible by standard stellar and binary evolutionary pathways.


MODEST is a loosely knit initiative of groups working in stellar dynamics, stellar evolution, stellar hydrodynamics, and observations of dense stellar systems. Our aim is to provide a comprehensive software framework for large-scale simulations of dense stellar systems, within which existing codes for dynamics, stellar evolution, and hydrodynamics can be easily coupled and compared to reality. The long-standing goal of combining "live" stellar evolution codes directly with N-body simulations has been realized, and we have reached consensus about software standards and interfaces, what is needed, and what is doable. On this web site we will provide up-to-date information about our activities, and pointers to various projects in progress, including coordination with Virtual Observatory projects around the world.

Other MODEST Initiatives

MODEST has spawned three important new initiatives in recent years. All are aimed at extending the MODEST goals in different ways.

  • The MUSE project, for MUltiscale MUltiphysics Simlation Environment, was begun at MODEST-6d in Amsterdam, in March, 2006. It is a multipurpose software environment for astrophysical applications in which different existing numerical codes are incorporated into a single framework. This component library provides easy access to individual packages and allows scientists to use combinations of codes to solve coupled problems in hydrodynamics, radiative transfer, stellar evolution, and stellar dynamics, without the need to write new codes or significantly alter existing codes. For more information, please see the MUSE wiki.

    Here is a movie created by Steve McMillan and Evert Glebbeek, using MUSE to combine a 4th-order Hermite N-body integrator written in C++ with a Fortran (77/90) implementation of Peter Eggleton's Twin stellar evolution code.

  • MICA, the Meta Institute for Computational Astrophysics, begun in 2007, is a virtual astronomical institute featuring many MODEST-related activities. Aimed at harnessing the capabilities of virtual worlds and 3D collaborative environments (such as Second Life, Qwaq, Wonderland, OpenSim), it fosters interaction among astrophysicists with interest in large-scale simulations, including dense stellar systems. Outreach and educational activities are also major MICA goals. MICA weekly events include popular talks, computational astrophysics lectures and Journal Club discussions of recent astro-ph papers. The MICA wiki, containing more information, schedules of events, and links to related pages, can be found here.

  • AMUSE, the Astrophysical Multipurpose Software Environment, is the successor to MUSE, building on the knowledge gained in developing MUSE and greatly expanding its capabilities. Begun in 2009 and centered at Leiden Observatory, AMUSE aims to provide a software framework for large-scale simulations of dense stellar systems, in which existing codes for dynamics, stellar evolution, and hydrodynamics can be easily coupled, and placed in an appropriate observational context. For more information, see the project documentation here.

The MODEST web site is hosted by the manybody consortium.

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Please direct comments, criticisms, corrections and contributions to Steve McMillan: steve (at) physics.drexel.edu.