An international research team used the ALMA antenna array to study the protoplanetary disk around the young star PDS 70. It managed to detect localized clusters of matter from which new exoplanets will form in the future.
To date, astronomers have discovered over 5,000 exoplanets. They are thought to have arisen from micron-sized dust grains in protoplanetary disks that surround young stars. However, how these dust grains accumulate in situ and lead to the formation of planetary systems remains unknown.
Located 370 light-years from Earth, PDS 70 is the only known star system where there are already two formed exoplanets within the protoplanetary disk, whose existence has been confirmed by optical and infrared observations. Clarifying the distribution of dust grains in this object will allow astronomers to better understand how they interact with each other and how they influence subsequent planet formation.
Previous ALMA observations at 0.87 mm have revealed ring-shaped emission from dust grains beyond planetary orbits. However, the radiation source may be optically thick (opaque when dust grains on the near side obscure those behind them), and the observed radiation distribution may not accurately reflect the distribution of dust grains.
Therefore, the researchers made new observations at a wavelength of 3 mm to more reliably determine the distribution of dust grains. They show that dust emission is concentrated in a particular direction in the dust ring outside exoplanets. This suggests that dust grains, which are the building blocks of exoplanets, accumulate in a narrow region and form a localized cluster.
The finding suggests that already-formed exoplanets interact with the surrounding disk, concentrating dust grains in a narrow region at the outer edge of their orbit. In the future, a new exoplanet grows out of these dust clumps. The formation of planetary systems such as our Solar System can be explained by the successive formation of planets from the inside out by repeating the process observed in PDS 70.
According to scientists, the discovery was a huge contribution to our understanding of exactly how exoplanets form. It also showed once again the importance of making observations in different wavelength ranges. In the case of PDS 70, the exoplanets were detected in the optical and infrared, while the protoplanetary disk was observed in the millimeter range.
Earlier we reported on how astronomers managed to find an exoplanet with a tail.
Provided by almaobservatory.org
