Comet tails: charged dust blowing in the solar wind

How a comet's dust tail forms bands stretching millions of kilometres across the sky has been observed for the first time by UCL scientists. The study, published today in Icarus, reveals the charged nature of the dust particles and the important role of the Sun in forming the characteristic patterns. An international team led by researchers from UCL Mullard Space Science Laboratory (UCL MSSL) successfully mapped the movement of dust particles in Comet C/2006 P1 McNaught, one of the brightest comets visible from Earth in the past 50 years. They used images collected from two NASA spacecraft - STEREO and SOHO - to track the behaviour of individual dust particles, which are about the same size as those found in cigarette smoke. Their findings indicate that the striations form when dust grains released from the comet's head break up into smaller particles, forming long bands. The smallest grains in the neat bands can later be moved around by the solar wind, changing the tilt of parts of the bands. "Understanding how dust behaves in the tail - how it fragments and clumps together - has important implications for understanding similar processes that formed dust into asteroids, moons and even planets billions of years ago," explained first author, PhD student Oliver Price (UCL MSSL).