- New simulations show that planets like Jupiter that form very far from their parent stars begin their lives not as a smooth sphere but rather as a flattened disk.
- Astrophysicists Adam Fenton and Dimitris Stamatellos from the University of Central Lancashire have produced a study that sheds light on the numerous different ways to grow a planet in the turbulent disk of dust and gas orbiting a baby star.
- It is unclear what the finding means for the core accretion model, but the study shows that the properties of a protoplanet embedded in a stellar disk may change depending on the viewing angle. For this reason, when looking at a planet from the side, its flat shape is more obvious, but when looking at the same planet from above, it is normal to think it is a sphere.
The formation of planets may not always occur as we imagine. New simulations show that large planets that form very far from their parent stars begin their lives not as a smooth sphere but rather as a flattened disk. This shape is called “oblate spheroid”. Protoplanets, which are planets in their developmental stages, slowly absorb matter as they rotate and eventually begin to become flat, like Jupiter.
Obtained by astrophysicists Adam Fenton and Dimitris Stamatellos from the University of Central Lancashire. findingsheds light on the countless different ways to grow a planet in the turbulent disk of dust and gas orbiting an infant star. Stamatellos says: “We have been studying planet formation for a long time, but we have never before considered controlling the shapes of planets in simulations. We always assumed they were spherical in shape. “When they first appeared, we were very surprised to see that they were shaped like bonbons.”
Although more than 5,500 planets have been found in the Milky Way to date, it is not clear exactly how they formed. When a star is born, it forms from a cluster in a large, dense cloud of gas and dust in space. This cluster collapses under gravity and begins to spin. The material around it forms a disk, rolling into the baby star and fueling its growth. This entire disk does not fall on the star. What remains is the other stuff that makes up a planetary system: Planets, comets, asteroids, moons…
So how does the material on the disc come together? For smaller terrestrial planets such as Earth, Venus, Mars and Mercury, scientists think they were built gradually by accumulating pieces of rock that stuck together and accumulated until they formed a planet.
For larger masses of gas, scientists believe something called disk instability may occur. This means that the rapidly cooling disk around the star breaks up into pieces that condense under gravity and turn into planets. This is an attractive idea because it could explain planets that are difficult to rationalize under accretion theory, such as planets that are much larger than expected relative to their star, planets at wide orbital separations, or rapidly forming large planets.
Fenton wanted to better understand the process of planet formation with disk instability. So he designed and ran complex simulations by varying different aspects of the process, such as gas density, temperature, and the speed of the disk. “This was an extremely challenging computing project requiring half a million CPU hours at the UK’s DiRAC (Distributed Research Using Advanced Computing) High Performance Computing Facility,” Fenton said. But the results were incredible and worth the effort.” says.
These results revealed that the gas masses first assumed a flattened shape as the protoplanets rotated, meaning that the centrifugal force and the protoplanet were still a relatively loose collection of matter at that stage. The simulation also showed that material accumulated on the growing protoplanet predominantly at the poles rather than at the equator.
It’s unclear what the finding means for the core accretion model, but the research shows that the properties of a protoplanet embedded in a stellar disk can vary depending on viewing angle. Because of all this, when a planet is viewed from the side, its flat shape is more visible, but when the same planet is viewed from above, it is normal to think it is a sphere. Researchers say we’re getting better at detecting these developing planets, so it’s important to understand how to interpret what we’re looking at.
Compiled by: Esin Özcan
