Planets form through domino effect

To date, more than 5,000 planetary systems have been identified. More than 1,000 of these systems have been confirmed to host multiple planets. Planets form in clouds of gas and dust around young stars, called protoplanetary disks. But the formation processes of multi-planetary systems, such as our solar system, remain poorly understood.

The best example of the formation of a multi-planetary system is a young star called PDS 70, located 367 light-years away in the direction of Centauri. It is the only object to have confirmed formed planets within a protoplanetary disk through optical and infrared observations (the first confirmed image of a newborn planet taken with the European Southern Observatory’s Very Long Telescope (ESO)). Previous radio wave observations using the Atacama Large Millimeter/submillimeter Array (ALMA) revealed rings of dust grains beyond the orbits of two known planets. But those observations were unable to get inside the ring to see the details.

In this study, an international team led by former PhD student Kiyoaki Doi. student at the National Astronomical Observatory of Japan (NAOJ)/University for Advanced Research SOKENDAI and currently a postdoctoral researcher at the Max Planck Institute for Astronomy, conducted high-resolution observations of the protoplanetary disk around PDS 70. Observed in longer wavelength radio waves. This is because longer wavelengths are better suited for observing dust clouds in protoplanetary disks.

The new ALMA observations clearly show that dust particles are concentrated to the northwest (top right) in a ring beyond the orbits of the two existing planets. The position of this dust clump suggests that the already-formed planet interacted with the surrounding disk, concentrating dust particles into a narrow region at the outer edge of its orbit. These accumulated dust particles are thought to grow into a new planet. This work shows through observations that the formation of planetary systems like the solar system can be explained by the repetition of the continuous formation process of planets from the inside out; like a row of falling dominoes, each one triggers the next.

New radio astronomy observations of planetary systems in the process of formation show that once the first planets form close to the central star, these planets can help guide material farther away to form new planets. In this way, each planet helps form the next, like a line of falling dominoes, with each planet triggering the next in turn.

To date, more than 5,000 planetary systems have been identified. More than 1,000 of these systems have been confirmed to host multiple planets. Planets form in clouds of gas and dust around young stars, called protoplanetary disks. But the formation processes of multi-planetary systems, such as our solar system, remain poorly understood.

The best example of the formation of a multi-planetary system is a young star called PDS 70, located 367 light-years away in the direction of Centauri. It is the only object to have confirmed formed planets within a protoplanetary disk through optical and infrared observations (the first confirmed image of a newborn planet taken with the European Southern Observatory’s Very Long Telescope (ESO)). Previous radio wave observations using the Atacama Large Millimeter/submillimeter Array (ALMA) revealed rings of dust grains beyond the orbits of two known planets. But those observations were unable to get inside the ring to see the details.

In this study, an international team led by former PhD student Kiyoaki Doi. student at the National Astronomical Observatory of Japan (NAOJ)/University for Advanced Research SOKENDAI and currently a postdoctoral researcher at the Max Planck Institute for Astronomy, conducted high-resolution observations of the protoplanetary disk around PDS 70. Observed in longer wavelength radio waves. This is because longer wavelengths are better suited for observing dust clouds in protoplanetary disks.

The new ALMA observations clearly show that dust particles are concentrated to the northwest (top right) in a ring beyond the orbits of the two existing planets. The position of this dust clump suggests that the already-formed planet interacted with the surrounding disk, concentrating dust particles into a narrow region at the outer edge of its orbit. These accumulated dust particles are thought to grow into a new planet. This work shows through observations that the formation of planetary systems like our solar system can be explained by the sequential formation of planets by repeating this process from the inside out; like a row of falling dominoes, each one triggering the next one.