Stars are the long-lived building blocks of galaxies. While most of them formed, almost all together, 10 billion years ago, new stars are still forming now, at a much lower pace. Star formation is the outcome of simultaneous accretion, driven by gravity, and ejection, powered by the energy of stars and black holes.
A most vexing concern is that everywhere, in the Early Universe as in our own Galaxy now, star formation is far less efficient than predicted by theory.
What is the missing piece in the puzzle?
Turbulence is a critical player, and the far-reaching question addressed in the MIST project is: can we measure the fraction of the large-scale gravitational energy stored (and eventually lost) in turbulence generated by the violent interplay between accretion and ejection?
The MIST project provides insights on a fundamental property of turbulence, its space-time intermittency, present in laboratory experiments, in the solar wind, in the physics of plasma confinement in the perspective of nuclear fusion. The challenge of the prodigious range of scales coupled by turbulence is also shared by climate sciences where turbulence in the oceans and in the atmosphere controls their exchange of matter and energy.
Astronomy is an important driver of advanced technology (interferometry, spectroscopy in the submillimeter range, space missions).
Last, human beings are curious of the Universe and are often grateful to researchers who dedicate their life to acquire this knowledge. As one of the 2020 Nobel prize of physics winners said " It is important to get people excited about research and astronomy has a special role to play". Humanity would not have evolved as it did without a knowledge of their sky.
The goal of the MIST project is therefore to follow the energy trail of baryonic matter in the star formation process from its source, the gravitational energy of the largest scales to its fate, its loss in radiative cooling.
The project involves complementary steps: (1) observations of lines emitted by molecular species, specifically formed and/or excited in turbulent dissipation bursts, (2) numerical simulations of magneto-hydrodynamical turbulence dedicated to dissipation scales to determine the nature of the dissipation structures, (3) modelling of the thermal and chemical properties of these structures, (4) novel statistical methods developed for the available observables to disclose the location of dissipation structures in the velocity field of cosmic turbulence.
