Molecules that are not electrically charged are unaffected by these magnetic fields. Type II tails comprise of dust, and are faintly yellow in colour because they reflect sunlight. Spectroscopic analysis of these tails shows that they are made up of silicate dust which is the main constituent of ordinary rocks on earth. By the influence of light pressure, some of these dust particles are swept away from the coma to form a tail. Only the very smallest dust particles, that have sizes close to the wavelength of yellow light, can be driven by radiation pressure in this way.
Dust tails show a distinct curvature.
This curvature is due to the speed of the dust particle as it is jetted off the comet s surface. Each dust particle has its own orbit around the sun, as predicted by Newtonian gravitation. Slower moving particles will have orbits further from the sun and faster moving particles will have orbits closer to the sun - hence the curvature in the tail. The Orrt Cloud. It is believed that comets come from the Oort Cloud , which is a collection of icy objects moving around the sun at a distance of at least a light year.