The planets in our solar system were born 4.6 billion years ago.
It is believed that the newly born sun was also about 30% darker than it is today.
And since the sun is a t-tauri-type star, it should be more active than it is today.
There were gases (volatile elements such as hydrogen and helium) and dust (rocky material) around the sun. But in the early days, they are thought to have gathered, electrically, like "dust. The gas and dust in the sun can make asteroids, which are small objects of meters in diameter, that cannot gather either gravitationally or electrically due to turbulence. But did they separate from the inner rocky planets and outer gaseous or Neptune-type planets of today? That's easy. Hydrogen and helium volatilize from the snow zone to the interior due to solar radiation. Therefore, they cannot acquire large amounts of gas and ice. Therefore, it is thought to be a rocky planet. Outside of that, gas (hydrogen and helium), ice, and dust remain without volatilizing, so Jupiter and Saturn could become giant gas giants. However, the outer planets such as Uranus and Neptune are assumed to have had low molecular density in the primordial solar nebula, and their formation stopped in the middle of growth. That would be the Neptune-type planets. Asteroid belts are thought to have failed to grow because Jupiter's gravity caused the asteroids to collide violently with each other. It is also possible that Kuiper Belt objects failed to form and formed as small bodies. In addition, super-Earths, which should be plentiful in exoplanet exploration, are not in the solar system, but may have been blown away by Jupiter, perhaps due to its gravitational influence. Other objects, such as Planet Nine, could be super-Earths or Neptune-type planets, but we do not know because the actual conditions have not yet been observed. It is not impossible that a super-Earth formed in the solar system may have been blown up to Jupiter. However, since there is no super earth in our solar system, we may have to observe other exoplanetary systems.
The Birth of the Planets in the Yang System
Moderator: Franck