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How are our solar systems formed?

A rapidly rotating disc of gas and dust once turned into planets, comets and asteroids, creating what is now our solar system. To understand this process, EU-funded astrophysicists added a key element to the picture: the heating of small regions in the protoplanetary disc.
How are our solar systems formed?
Given that compression heats gas, the rotating cloud of gas and dust was heated while the protoplanetary disc contracted. However, once it stopped contracting, stabilised by rotation, it ceased heating and began cooling as it radiated energy away into the near absolute zero space. Eventually, it cooled so much that a new process commenced.

Tiny solid flakes and grains formed within it, from which a solar system was ultimately built up. During mass accretion, the magnetorotational instability should have acted, producing turbulence. But the magnetised turbulence dissipated its energy intermittently, determining the structure of accreting regions.

The aim of the project COOKINGDUSTINDISKS (Forming high-temperature solids in protoplanetary disks) was to shed light on this energy dissipation of magnetised turbulence, heating the discs locally. To this end, astrophysicists used high-resolution numerical models.

The model predictions showed, for the first time, differential rotation shearing magnetic fields that, in turn, created small regions several hundred Kelvin hotter than the surrounding gas. The temperature variations observed were large enough to have consequences on mineral formation.

Such heating events can play a major role in melting chondrules, remelting calcium-aluminium-rich inclusions and annealing silicates, namely materials found in meteorites. In their efforts to simulate protoplanetary discs, astrophysicists initially studied a small portion of the disc in order to save on computing costs.

However, 'global magnetohydrodynamic' (MHD) simulations of protoplanetary discs were later carried out and revealed surprising magnetic field structures. A qualitatively different current sheet structure was observed in a largely non-turbulent region driven by processes captured by the generalised local model.

Knowledge gained through work on the role of magnetic fields in protoplanetary discs was then used to explore the Rossby wave instability. This instability can develop during the transition of poorly ionised regions to magnetised zones of protoplanetary discs and contribute to planet formation.

3D MHD simulations showed how, under specific conditions, large vortices are formed and are capable of trapping dust and concentrating it in planetesimals, comets and asteroids. A movie compiled from the simulation results has been uploaded here.

The many fascinating results of COOKINGDUSTINDISKS are described in a series of publications in high-impact peer-reviewed journals. Supported by observations of protoplanetary discs similar to our early solar system, they succeeded in building a better understanding of how an interstellar cloud collapsed to form our solar system.

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Solar system, planets, comets, asteroids, protoplanetary disc, COOKINGDUSTINDISKS
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