We report how the action of radiation forces on small solid particles in a circumstellar disk could induce a suitable mechanism for orbital migration of protoplanets. Since the ratio of radiation-to-gravitational forces acting on a particle depends on its physical and chemical properties, different particles following the same trajectory move with

The main problem in using the inverse Abel transform of an experimentally observed function is that it involves numerical differentiation, which amplifies the errors affecting the measurements. This difficulty can be overcome by using spectral expansion methods, with coefficients obtainable through a numerical integration. The inaccuracy of the

The amount of data produced by large observational facilities and space missions has led to the archiving and on-line accessibility of much of these data, available to the entire astronomical community, and allowing a much wider multi-frequency approach of astronomical research than previously possible. Here I intend to draw attention to these

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