The World of Comets

according action already amongst apparition appeared astronomers atmosphere become bodies bright brilliant calculated called cause celestial centre century changes comet cometary compared considered continuous course curve described determined diameter direction discovered distance distinct drawing earth eccentricity effect elements elliptic equal example explain fact force further give given greater head heavens idea inclination increase influence July Jupiter kind known least length less light longitude luminous mass matter mean mention meteors miles motion move movement nature nearly nebulosity node November nucleus observed October opinion orbit origin parabolic passage passed perihelion period perturbations phenomena physical planets portion position prediction present probable question rays reason regarded region remarkable respect result seen similar situated solar space spectrum stars suppose tail telescope theory true visible