The elements of astronomy; a textbook . ormation of a Cornets Tail byMatter expelled from the Head. According to this theory, thetail is simply an assemblage ofrepelled particles, each moving inits own hyperbolic orbit aroundthe sun, the separate particles hav-ing very little connection with oreffect upon each other, and beingalmost entirely emancipated fromthe control of the comets the force of the projection is seldom very great, all these orbitslie nearly in the plane of the comets orbit, and the result is that thetail is usually a sort of a flat, hollow, curved, horn-shaped cone
The elements of astronomy; a textbook . ormation of a Cornets Tail byMatter expelled from the Head. According to this theory, thetail is simply an assemblage ofrepelled particles, each moving inits own hyperbolic orbit aroundthe sun, the separate particles hav-ing very little connection with oreffect upon each other, and beingalmost entirely emancipated fromthe control of the comets the force of the projection is seldom very great, all these orbitslie nearly in the plane of the comets orbit, and the result is that thetail is usually a sort of a flat, hollow, curved, horn-shaped cone, openat the large end, as represented by Fig. 96. 389. Curvature of the Tails andTails of Different Types. —The tail is curved, because the re-pelled particles after leaving thecomets head retain their originalmotion, so that they are arrangednot along a straight line drawnfrom the sun to the comet, buton a curve convex to the direc-tion of the comets motion, as shown in Fig. 97: but the stronger the repulsion the less Fig. Comets Tail as a Hollow Cone. § 3S9] CURVATURE OF THE TAILS. 279 Bredichin (of Moscow) has found that in this respect thetrains of comets may be classified under three different types,as indicated by Fig. 98. First, the long, straight rays: they are composed of matter uponwhich the solar repulsion is from 12 to 15 times as great as the gravi-tational attraction, so that the particles leave the comet with a relativevelocity of four or five miles a second, which is afterwards continu-ally increased until it becomes enormous. The nearly straight raysshown in Fig. 89 belong to this type. For plausible reasons, con-nected with its low density, Bredichin considers them to be composedof hydrogen, possibly set free by the decomposition of are rather uncommon, and in no case have been bright enoughto allow a spectroscopic test of their nature.
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