Atmospheric Trajectory of a Meteoroid

Abstract

You have probably been surprised on many occasions by the sight of a meteor in the night sky. Depending on which country you are from, you may have done any of a dozen different activities on such an occasion: kissing your partner; making a wish; just marveling at the sudden change in the sky. During some rich meteor showers you may get tired of all these activities. A typical maximum for the Perseids would allow about 60 wishes per hour while some of the richest displays of meteor showers (Leonids, Draconids) can surprise you with an hourly rate of several tens of thousands of meteors (such a high activity would be quite exceptional). Because the shower meteors come to the Earth in almost parallel trajectories they seem to radiate from one point (or one very small area) in the sky and the name of the shower is derived from the constellation where this point, the radiant, is located. The hourly rates are usually normalized to the ideal position of the radiant, the zenith, where the meteors would move vertically. However, most meteors do not belong to a distinct shower. We call them sporadic meteors, but we can still speak about the radiant of one meteor; it is simply the direction of the meteoroid motion. If you see the same meteor from many different locations, it projects to different parts of the sky, but all these apparent trails (great circles), extrapolated backwards, intersect at one point, the radiant.