Planets Form Through Domino Effect - UNIVERSE

New radio astronomy observations of a planetary system in the process of forming show that once the first planets form close to the central star, these planets can help shepherd the material to form new planets farther out. In this way each planet helps to form the next, like a line of falling dominos each triggering the next in turn.

To date over 5000 planetary systems have been identified. More than 1000 of those systems have been confirmed to host multiple planets. Planets form in clouds of gas and dust known as protoplanetary disks around young stars. But the formation process of multi-planet systems, like our own Solar System, is still poorly understood.

The best example object to study multi-planet system formation is a young star known as PDS 70, located 367 light years away in the direction of the constellation Centaurus. This is the only celestial object where already-formed planets have been confirmed within a protoplanetary disk by optical and infrared observations (First Confirmed Image of Newborn Planet Caught with ESO’s VLT (ESO) ). Previous radio wave observations with the Atacama Large Millimeter/submillimeter Array (ALMA) revealed a ring of dust grains outside the orbits of the two known planets. But those observations could not see into the ring to observe the details.

In this research, an international team led by Kiyoaki Doi, formerly a Ph.D. student at the National Astronomical Observatory of Japan (NAOJ)/the Graduate University for Advanced Studies, SOKENDAI and currently a postdoctoral fellow at the Max Planck Institute for Astronomy, performed high-resolution observations of the protoplanetary disk around PDS 70. The team again used ALMA, but observed at a longer wavelength of radio waves. This is because longer wavelengths are better for peering into the dusty cloud of the protoplanetary disk.

The new ALMA observations clearly show a concentration of dust grains to the north-west (upper right) in the ring outside the orbits of the two existing planets. The location of this dust clump suggests that the already-formed planets interact with the surrounding disk, concentrating dust grains into a narrow region at the outer edge of their orbits. These clumped dust grains are thought to grow into a new planet. This work observationally shows that the formation of planetary systems, like the Solar System, can be explained by the sequential formation of the planets from inside to outside by the repetition of this process; like a line of falling dominos, each one triggering the next.

Source: https://www.nao.ac.jp/en/news/science/2024/20241213-alma.html

Image: Compared to the previous observations (left), the new ALMA observations (right) at longer wavelengths can better see into the dust ring and reveal a concentration of dust to the north-west (upper right) where a new planet is forming. (Credit: ALMA (ESO/NAOJ/NRAO), W. M. Keck Observatory, VLT (ESO), K. Doi (MPIA))

Journal article: https://www.soken.ac.jp/en/news/2024/20241213.html  

Source: Planets Form Through Domino Effect – Scents of Science