If these studies are confirmed by observations, it could change the understanding of the process of planet formation and force astrophysicists to reconsider it
Astrophysicists from the University of Central Lancashire (UCLan) have discovered that the planets immediately after formation have an oblate shape, and not spherical, as previously thought. The team used computer simulations of planet formation consistent with the protoplanetary disk instability theory, which proposes that protoplanets form quickly as a result of the breakup of large rotating protoplanetary disks.
Using this approach, the team determined the properties of exoplanets, compared them with observations, and investigated the formation mechanism of gas giant planets. Scientists have focused on studying the shape of young planets and how they become large gas giant planets – larger than Jupiter. They also examined the properties of planets forming under different conditions, such as ambient temperature and gas density.
Dr Adam Fenton, who led the study, said: «Over the past three decades, many exoplanets have been discovered, which are planets orbiting stars in other solar systems. Despite observing many thousands of them, how they form remains unexplained. They are thought to form either through core accretion—the gradual buildup of dust particles that clump together to form larger and larger objects over long periods of time—or through the collapse of large spinning protoplanetary disks around young stars in short periods of time, which we call & ;ldquo;disk instability theory”. This theory is attractive because large planets can form very quickly at great distances from their star, which could explain some observations of exoplanets. This was an extremely computationally intensive project, requiring half a million processor hours at the UK high-performance computing center DiRAC. But the results are amazing and worth the effort».
Dr Dimitris Stamatellos, lecturer in astrophysics at UCLan and co-author of the study, added: «We have been studying planet formation for a long time, but never before has it occurred to us to test the shape of planets as they form in simulations. They were always assumed to be spherical. We were very surprised when they turned out to be oblate spheroids».
Observational confirmation of the flattened shape of young planets may answer the question of how planets form, pointing to the currently less popular model of disk instability rather than the standard theory of planet formation by core accretion.
Researchers also found that new planets grow as material accumulates on them, mostly from the poles rather than the equators.
These results have important implications for observations of young planets because they suggest that the way planets appear through a telescope depends on the viewing angle. Such observations of young planets are important for understanding the mechanism of planet formation.
The researchers plan to build on this discovery with improved computational models to study how the shape of planets is affected by the environment in which they form and to determine their chemical composition for comparison with future observations by the James Space Telescope Webb».