ALMA observes dust clump where a new planet may form

ALMA observes dust clump where a new planet may form
by Clarence Oxford
Los Angeles CA (SPX) Dec 17, 2024

The Atacama Large Millimeter/submillimeter Array (ALMA) has uncovered critical details about planetary system formation by detecting a dense concentration of dust grains outside the orbits of two known planets in the protoplanetary disk surrounding the young star PDS 70. These findings, led by Kiyoaki Doi, a researcher at the Max Planck Institute for Astronomy and former Ph.D. student at the National Astronomical Observatory of Japan (NAOJ), shed light on how already-formed planets influence subsequent planet formation.

PDS 70 is unique as the only known system hosting planets within its still-forming protoplanetary disk. Using ALMA's high-resolution observations at a wavelength of 3 mm, researchers successfully mapped the distribution of dust grains in this system. Unlike earlier observations at 0.87 mm, which suggested a ring-shaped dust emission, the new data revealed a concentrated accumulation of dust in a specific direction outside the planetary orbits. This clumping highlights a localized region where dust grains gather, potentially marking the early stage of another planet's birth.

"A celestial object is made up of multiple components, each emitting radiation at different wavelengths. Thus, observing the same object at multiple wavelengths offers a unique perspective on the target. In PDS 70, the planets were discovered at optical and infrared wavelengths, while the protoplanetary disk was observed at millimeter wavelengths. This work shows that the disk exhibits different morphologies, even within the observation wavelength range of ALMA. This highlights the importance of observations across various wavelengths, including multi-wavelength observations with ALMA. Observing multiple components of a target with various observational settings with different telescopes is necessary for a comprehensive understanding of the entire system," said Kiyoaki Doi.

The findings suggest that the two known planets in the PDS 70 system interact gravitationally with the surrounding disk, concentrating dust grains at the outer edge of their orbits. These dust grains, considered building blocks of planets, are likely to grow into a new planet over time. Such sequential formation, where planets emerge from inside to outside in protoplanetary systems, may explain the development of multi-planet systems like our Solar System.

ALMA's ability to observe longer wavelengths, such as 3 mm, provides a clearer view of dust grain distribution due to its transparency, offering a more reliable measurement than shorter wavelengths. This advancement underscores the importance of multi-wavelength studies to fully understand how planetary systems evolve.

These results significantly advance our understanding of planetary system formation, showcasing how existing planets interact with their environment to trigger subsequent planetary growth.

Research Report:Asymmetric Dust Accumulation of the PDS 70 Disk Revealed by ALMA Band 3 Observations