In a recent study published in the journal Astronomy & Astrophysics, a team of researchers led by Zoe Roumeliotis from the University of Cambridge has shed new light on the process of terrestrial planet formation. The team, which includes Luca Matrà, Grant M. Kennedy, Sebastian Marino, Kate Y. L. Su, David J. Wilner, Mark C. Wyatt, and Alan P. Jackson, all affiliated with the University of Cambridge’s Institute of Astronomy, used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the debris disk around the star HD 172555.
The researchers focused on the distribution of millimeter-sized grains in the debris disk, which is believed to have been created by a giant impact between planetary embryos. Such impacts are thought to be a natural step in the formation of terrestrial planets, and understanding the resulting debris can help constrain models of planetary collisions.
Using ALMA’s high-resolution capabilities, the team was able to resolve the distribution of millimeter grains in the debris disk for the first time. They found that the disk extends out to about 9 astronomical units (au) from the central star and is inclined relative to our line of sight. The researchers did not detect any significant asymmetry in the dust distribution, suggesting that the impact that created the disk was relatively recent and that the debris has not yet had time to spread out evenly.
The team also used radiative transfer modeling to infer the surface density distribution of the millimeter grains. They found that the density most likely peaks around 5 au from the star, although the exact width of the distribution remains model-dependent. Interestingly, the researchers noted an outward radial offset of the small grains traced by scattered light observations compared to the millimeter grains. They suggest that this offset could be explained by the combined effect of gas drag and radiation pressure in the presence of large enough gas densities.
Furthermore, the researchers used spectral energy distribution (SED) modeling to infer the size distribution of the grains. They found that the size distribution slope for the millimeter grains is consistent with the expectation of collisional evolution and is flatter than that inferred for the micron-sized grains. This suggests a break in the grain size distribution and confirms an overabundance of small grains in the debris disk.
The findings of this study have important implications for our understanding of terrestrial planet formation. By constraining the models of planetary collisions, researchers can better understand the processes that lead to the formation of Earth-like planets. Additionally, the study highlights the importance of high-resolution observations in studying debris disks, as they can provide valuable insights into the distribution and composition of the debris.
In summary, the team led by Zoe Roumeliotis has used ALMA to resolve the distribution of millimeter grains in the debris disk around HD 172555. They found that the disk extends out to 9 au and is inclined, with no significant asymmetry in the dust distribution. The surface density of the millimeter grains peaks around 5 au, and there is an outward radial offset of the small grains compared to the millimeter grains. The size distribution of the grains suggests a break in the distribution and an overabundance of small grains. These findings provide valuable insights into the process of terrestrial planet formation and the role of giant impacts in shaping the debris disks around young stars.
This article is based on research available at arXiv.