Easy AU to light years conversion. An astronomical unit is the average distance between the Earth and the Sun. Estimates of this distance have varied over time. It is now defined as exactly 149,597,870.7 kilometers. A light year is the distance that light travels in one year. The year used by the International Astronomical Union is 365.25 days. transfer calculation of a protoplanetary disk characterized by a vortex created by the tidal interaction with a massive planet. As a case study, the disk parameters are chosen to mimic the IRS 48 system, ... (<1 AU), those responsible for the accretion onto the star, might be more viscous than the disk re-gions probed by current spatially.