 The IAU's definition does not attach specific numbers or equations to this term, but all the IAU-recognised planets have cleared their neighbourhoods to a much greater extent (by orders of magnitude) than any dwarf planet, or any candidate for dwarf planet.The phrase stems from a paper presented to the 2000 IAU general assembly by planetary scientists Alan Stern and Harold F. Levison.The authors used several similar phrases as they developed a theoretical basis for determining if an object orbiting a star is likely to "clear its neighboring region" of planetesimals, based on the object's mass and its orbital period.