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To explore this phenomenon, Dr. Sota Arakawa, a Young Research Fellow in the Center for Mathematical Science and Advanced Technology at JAMSTEC, collaborated with his team to conduct a series of comprehensive numerical simulations. These simulations used soft-sphere discrete element methods to observe the collision of two solid microparticle aggregates. By modeling collisions between aggregates ranging in size from approximately 10,000 to 140,000 particles, the team intended to determine the "sticking probability" - the likelihood that after colliding, the two aggregates would remain adhered, forming a larger composite.
The researchers' intensive computational efforts were carried out on the PC cluster at the National Astronomical Observatory of Japan (NAOJ). The findings, which represent a first in computational research, unveiled an unexpected trend: as the radius of the colliding aggregates increased, the sticking probability diminished. Simply put, larger aggregates exhibited a reduced tendency to coalesce after collision.
This revelation has far-reaching implications for our understanding of planet formation. Planetesimals, often termed the "seeds" of planets, are generally believed to emerge through numerous collisions and subsequent mergers of solid microparticles within protoplanetary disks. These planetesimals are kilometer-sized celestial entities seen as the foundational blocks from which planets are sculpted. They undergo formation from micron-sized solid microparticles, eventually amassing to become full-fledged planets, courtesy of collisional merging propelled by mutual gravitation.
Yet, this recent study has illuminated a considerable stumbling block in this assumed trajectory of planet formation. The results suggest that the direct collisional growth of cosmic dust microparticles to shape planetesimals might be obstructed by what can be described as a "collisional bouncing." As these aggregates grow in size, their propensity to bind together after a collision becomes increasingly unlikely. This poses an intrinsic challenge for the formation of planetesimals through the direct collisional growth pathway, providing a renewed perspective on the intricate processes underpinning planet genesis.
In essence, this discovery underscores the complex dynamics at play within our universe. With every research endeavor, we edge closer to fully understanding the vast and intricate tapestry of celestial evolution. With findings like these, we're reminded that there's still much to learn about the cosmic dance that results in the birth of planets.
Research Report:Size Dependence of the Bouncing Barrier in Protoplanetary Dust Growth
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