The solar system rotates in surprising ways. Astrophysics explain the mystery

In theory, it would seem that the inner part of the young solar system should move faster than the outer part. But why didn’t that happen?

Paul Bilan and Yang Zhang of the California Institute of Technology have created a model of a hypothetical rotating accretion disk. It consisted of about 40,000 neutral particles and about 1,000 charged particles that could collide with each other, taking into account the influence of gravity and the magnetic field. It was equivalent to a huge number of neutral particles, electrons and ions colliding with each other, orbiting in the magnetic field around a young star like the Sun.

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The disks of dust and gas orbiting around young stars are known as accretion disks. It is made up of a small part of the mass of the star it orbits. According to scientists, this spiral should be distinguished by the fact that its inner part will rotate faster and faster, according to the law of conservation of angular momentum. This can be compared to snowboarders who start to spin faster when they stop spreading their arms and bringing them closer to the body.

Since the helical motion of the accumulator disc can be considered similar to that of skaters, the inner part of the accumulator disc must rotate faster than the outer part. The actual results, however, do not agree with what the law of conservation of angular momentum suggests. Among the proposed explanations for this phenomenon are, among other things, references to the friction between the inner and outer parts of this disc. Even the so-called magnetic instability, due to the appearance of magnetic and gaseous disturbances, which leads to friction and lowering the rotational speed.

The young solar system was created from the so-called accretion disk

Bilan and Zhang presented their findings in the pages Astrophysical Journal. Their research concerns how individual gas molecules behave when they collide with each other. Additionally, the study authors focused on how these particles move between collisions. The initial hypothesis was that the difference between the interactions was the basis for the rotation of the accumulation discs. If the electrons and ions are affected by both gravity and the magnetic field, then the neutral atoms in this case will be limited only by gravity.

The aforementioned simulations showed that collisions between neutral atoms and a much smaller number of charged particles led to a situation in which positively charged ions moved inward toward the center of the disk, and negatively charged particles moved outward. A separate class would be neutral particles that lose angular momentum and rotate toward the center.

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The so-called canonical angular momentum, which in the case of charged particles is very different from the normal angular momentum. Since the electrons are negative and the cations are positive, the internal movement of the ions and the external movement of the electrons intensify the legal angular momentum of these particles. The neutral loses angular momentum as a result of collisions with the charged particles and moves inward, compensating for the increase in the primary angular momentum of the charged particles. Bilan and Zhang demonstrated this on a small scale, but it actually affects entire stars and their discs.