Debris disks are the natural byproduct of the planet formation process. They are disks surrounding stars, created by collisions of planetesimals that have formed in younger stages of the systems, when the stars are still surrounded by large amounts of gas. The process of planet formation releases a large amount of micrometer-sized dust grains, whose half-life is much shorter than the typical age of the star, so they have to be continuously replenished from larger bodies. The “survival time scales” for dust grains are affected by different processes mostly related to the host star of the system. Stellar winds are theoretically thought to be likely dominant in this respect, but very poorly constrained observationally., particularly in the case of low-mass stars
Given the small number of spatially resolved observations of debris disks, especially around stars with half (or less) the mass of our Sun, we still know very little about them.
A team of astrophysicists, led by Christian Adam, a postdoctoral researcher from the Millennium Nucleus for Planet Formation (NPF) and the Max Planck Tandem Group at Universidad de Valparaíso (MPTG), compared near-infrared observations of the system (star surrounded debris disk) GSC 07396-00759 with a radiative transfer model to study the disk morphology, and probe the properties of the dust in the disk under the influence of the stellar radiation pressure and winds. The research also involved Johan Olofsson, NPF research associate and MPTG leader, Amelio Bayo, NPF’s director, and Matias Montesinos, NPF’s adjunct researcher and Universidad Viña del Mar faculty.
Dr. Adam points out that debris disks around low-mass stars are very interesting objects, especially with regard to the possible connection between their appearance and the presence of planets. Although only about 2% of M stars have been found to harbor giant planets, rocky planets seem to be detected more frequently around and debris disks are thought to be the nurseries for rocky planetary formation.
This research, combining observations and modeling, concluded that the stellar winds on GCS 07396-00759 could be as strong as 500 times that of our sun. “Therefore, they could play a dominant role in transporting particles to the outer disk that otherwise remain closer to their parent bodies,” explains the scientist.
“The excellent resolution of current generation telescopes such as the VLT, the capabilities of instruments such as SPHERE/IRDIS, and advances in modeling and interpretation of observations that help us to better understand not only how stellar systems form and evolve, but also to better understand how our own solar system evolved and how it differs from other extrasolar systems,” emphasizes Adam.
The future steps of this project involve combining observations from different telescopes and wavelengths to obtain a more complete picture of the disk structure, distribution and properties of the dust grains within the disk.
“In addition, and in particular in the case of young low-mass stars, such as GSC_07396-00759, the influence of stellar activity, especially stellar winds, or stellar flux fluctuations caused by intense and frequent eruptions remains rather unclear and should also be taken into account to better understand the influence of the different pressure forces acting on the dust grains that are responsible for the observed disk morphology,” concludes the astrophysicist.