Over a period of two million years, Jupiter grew slowly. This had already been suggested by studies on meteorites. Astronomers from the Universities of Berne and Zurich, as well as ETH Zurich, have tried to clarify how this came about. With a new model, they have traced the emergence of the gas giant and solved the mystery.
“We were able to show that Jupiter has grown in different phases,” summarized Julia Venturini from the University of Zurich. The results of the study have been published in the journal “Nature Astronomy”. Accordingly, in these phases the gas giant did not steadily increase in mass.
First, the planetary embryo collected small sinews only a few centimeters in size and quickly formed a planetary nucleus during the first million years. In the second phase, the following two million years, the growth slowed down. The reason for this was, according to the researchers, are the collisions with kilometer-sized chunks, which slowly added more mass, but provided a lot of energy.
The clashes with these chunks released heat. The heat in turn heated up the gas atmosphere of young Jupiter and prevented rapid cooling, contraction and further gas enrichment. Thus, one can explain the relatively long period spent by Jupiter in the mass range of 15 to 50 earth masses, as the researchers write. Only in the third phase did gases finally accumulate and make Jupiter a gas giant with around 300 times the mass of the earth and a diameter of around 143,000 kilometers.
The study has triggered recent measurements of the composition of meteorites. These had revealed that the young solar system, when it was still a disk of dust and gas, was divided into two regions. Apparently Jupiter represented the dividing barrier. During two million years, when Jupiter grew from 20 to 50 Earth masses, it apparently disturbed the dust disk and must have produced an over-seal, the researchers said. The result was that material outside its orbit could not mix with the material within its orbit. This separation lasted until Jupiter had accumulated enough mass to redirect rocks and scatter them into the inner regions of the solar system.