Sec. 2.1 Origin of Planets
-Formation of early planets from viewpoit of matterial science-
Sec. 2.1.1 The birth of the Sun and Planets
-The scenario of the birth of the solar system-
The theories of the formation of the solar system include the agglutination theory and the giant impact theory. In the standard model scenario of the formation of the solar system, a proto-solar disk was formed from an interstellar molecular cloud, and planetesimals were formed in the dust layer, which became protoplanets and formed planets. However, the explanation that the lightest hydrogen molecules first gathered by gravity to form the Sun will not convince.
In the current solar system, the mass of the Sun is 99.86%, and the primordial Sun, which was in the center of the planetary solar system, rapidly grew to become huge. Planets are only about 0.14% of the total mass of the solar system. The planet's orbit is described by Kepler's third law of the gravitational field at the center of the planet. The orbits are determined by the following equation.
(r3/T2)=G(m+M)/(4π2) Here, [M] is the mass of the Sun and [m] is the mass of the planet. Since the current orbit of the planet is close to a circle and the rotation period is almost inversely proportional to the mass of the planet, it can be explained that the interstellar medium that formed the planet is the material that continued to orbit the Sun.
In other words, matter in the same orbits is orbiting at almost the same
speed, regardless of size. Matter orbiting in the same orbit at the same
speed slowly encounters each other, and when atoms approach each other
to about the interatomic distance, the positive and negative charges of
the material do not cancel each other, and they interact chemically. At
a distance of atomic size, the force of the Coulomb force is 10< >
36 times greater than the force of universal gravitation. Therefore, if
the Sun and planets were born at the same time, the Sun, which was at the
center of gravity in the solar system, grows rapidly, but the growth rate
due to the accretion of celestial bodies with small masses is very slow.
At the beginning of the birth of celestial bodies, gravity was weak, so H₂O and CO₂ came into contact as ice and dry ice and began to grow as a mass. The interstellar medium in the same orbit merged to form a mass, and the mass became a planet.
Sec. 2.1.2 Growth of celestial bodies due to collisions between small materials
-The mechanism by which the interstellar medium of the same orbit collide
and the planets grow.-
When a solid of cosmic dust comes into contact with a solid, it binds locally at the point of contact and forms a mass.
Even if small chunks of interstellar medium in the same orbit approach each other, the impact of the collision is weak because the gravity of each is weak. If the particles come into gentle contact, they will adhere to each other due to intermolecular forces and become a mass, resulting in a stable low energy state.
As the planet grows, so does the energy of the impact of falling meteorites. Meteorite impacts cause the surface of the planet to become hotter. Meteorite crashes do not raise the temperature of the planet's core.
The pressure increases inside a large mass of celestial bodies, and the higher the pressure, the higher the temperature.
When larger planets approach each other on the same orbit, the universal gravitational force between them becomes stronger, and a "giant impact" occurs. Even after the collision, the added center of gravity will remain the same as it orbits in its orbit. Eventually, the debris scattered by the impact will be collected at the center of gravity and become a large planet. In this way, we propose a scenario for the formation of the solar system,
in which cosmic dust clumps and becomes planetesimals in orbit of the gravitational
field of the center of the clumps, planetesimals become asteroids, and
asteroids become planets. (May 17, 2025） (Photo courtesy of Pixta7751137)
Sec. 2.1.3 Formation of terrestrial planets -Effects of the solar wind-
Celestial bodies such as planets are matter, and the process of first forming celestial bodies is due to short-range forces such as the Coulomb force. The action of that force is the close distance, which is discussed in units of angstroms (10-10m). Universal gravitational force cannot explain the formation process of objects. In the world at the atomic level, universal gravitational force is 35 orders of magnitude smaller than short-range force.
The Sun, like the planets, is thought to have grown as a mass after the interstellar medium first came into silent contact with each other and adhered to it by intermolecular bonds. The center of the solar system has a high concentration of interstellar medium, and the growth rate of the Sun is fast and significantly larger. Microscopic particles play a role in holding solids together. However, it is difficult for rocky planets to be born in an environment where the solar wind blows away water molecules and particles.
J. S. Lewis examined the internal structure of planets and moons and proposed the equilibrium condensation theory (1974), which states that celestial bodies were created from materials that solidified at lower temperatures as they moved farther from the Sun.
This equilibrium condensation theory explains that the outer planets were born almost at the same time as the Sun, but if the proto-solar nebula was about 2000°C, the internal layer structure of the current planet was almost completed at that time [5].
However, the early high temperature of the solar system must be caused by the nuclear fusion of the Sun, and the planets of the solar system had formed until the solar wind began to blow then. It follows that the meteorites were ejected from the Sun’ nuclear fusion and collided with the planet and created a "magma ocean" on the surface of the terrestrial planet, and the gaseous components taken in at that time were released, creating a large amount of carbon dioxide atmosphere on Venus and a large amount of seawater on the Earth [5]. In addition, the fact that the rotation of Venus is in the direction of clockwise rotation can be explained by the fact that the solar wind, which has a counterclockwise rotation component, collided head-on with the center near the equator and caused a "superrotation" in the atmosphere in the direction of clockwise rotation[6]。
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[ Resources ]
[5] Masahiko Akiyama , "The Atmosphere of the Atmosphere",pp.25,
Aoki Shoten, February 1987.
[6] Shinji Karasawa , "Comparative Planetary Studies based on Theory
of Materiality" 2017.
http://www7b.biglobe.ne.jp/~shinji-k/Eg%20planetology%20page4.htm
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