Debris disks don`t need planets to form rings

Washington: A new study has found that a debris disk does not need planets to produce narrow rings on its own.

"When the mass of gas is roughly equal to the mass of dust, the two interact in a way that leads to clumping in the dust and the formation of patterns," lead researcher Wladimir Lyra, a Sagan Fellow at NASA`s Jet Propulsion Laboratory in Pasadena, California, said. "In essence, the gas shepherds the dust into the kinds of structures we would expect to be seen if a planet were present," he said. The warm dust in debris disks is easy to detect at infrared wavelengths, but estimating the gas content of disks is a much greater challenge. As a result, theoretical studies tend to focus on the role of dust and ice particles, paying relatively little attention to the gas component. Yet icy grains evaporate and collisions produce both gas and dust, so at some level all debris disks must contain some amount of gas. "All we need to produce narrow rings and other structures in our models of debris disks is a bit of gas, too little for us to detect today in most actual systems," co-author Marc Kuchner, an astrophysicist at NASA`s Goddard Space Flight Center in Greenbelt, Md, said. Here`s how it works. When high-energy ultraviolet light from the central star strikes a clump of dust and ice grains, it drives electrons off the particles. These high-speed electrons then collide with and heat nearby gas. The rising gas pressure changes the drag force on the orbiting dust, causing the clump to grow and better heat the gas. This interaction, which the astronomers refer to as the photoelectric instability, continues to cascade. Clumps grow into arcs, rings, and oval features in tens of thousands of years, a relatively short time compared to other forces at work in a young solar system. The study is published in the journal Nature. ANI