All About Space: Young giant planets are born from gas and dust. Researchers of ETH Zurich and the Universities of Zurich and Bern simulated different scenarios relying on the computing power of the Swiss National Supercomputing Centre (CSCS) to find out how they exactly form and evolve. They compared their results with observations and were able to show amongst others a big difference between the postulated formation mechanisms. Astronomers set up two theories explaining how gaseous giant planets like Jupiter or Saturn could be born. A bottom-up formation mechanism states that first, a solid core is aggregated of roughly ten times the size of the Earth. “Then, this core is massive enough to attract a significant amount of gas and keep it,” explains Judit Szulágyi at the ETH Zurich and member of the Swiss NCCR PlanetS. The second theory is a top-down formation scenario: Here the gaseous disc around the young star is so massive, that due to self-gravity of the gas-dust, spiral arms are forming with clumps inside. Then, these clumps collapse via their own gravity directly into a gaseous planet, similar to how stars form. The first mechanism is called “core-accretion”, the second one “disc instability.” In both cases, a disk ...