Frank W. Very
Published: 2017-10-20
Total Pages: 192
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Excerpt from Occasional Scientific Papers of the Westwood Astrophysical Observatory: Numbers 1-3 The word albedo (derived from the Latin albus, white) has been used by astronomers to designate the fraction of the sun's luminous rays reflected by a planet at full phase, allowance being made for the distances of the planet from sun and earth and for the dimensions of the. Reflecting body. If the planet were a smooth sphere with perfect specular reflection, it would be itself invis ible, but would present within the diminutive limits of its disk a complete picture of the surrounding heavens, distorted by, spher ical aberration, but' otherwise exact; and within this image the reflection of the sun would surpass in brilliancy all other objects, shining, like a star at a point on the planet's disk distant from the center by the radius of the disk multiplied by the cosine of half the elongation of the planet from the sun. But whatever specular surfaces there may be on the planets of our solar system, they are of too limited extent to be recognized as such; and the plane tary reflection of light is to be classed under the head of a gen erally diffusive one, though not necessarily an equable one in all directions; and in fact there are diversities in the distribution of the reflected light to different parts of the sphere which must be considered in getting the phase-curve of the illumination, and which are not entirely without influence even if we confine our attention to the reflection sent earthward at full phase, while they are vital to the determination of the complete reflection to the sphere. Since all of the planets, except possibly some of the smaller asteroids, are spheroidal bodies, it is not necessary for purposes of intercomparison to refer their albedoes to the standard specific reflectivity of a flat surface; but it is desirable to distinguish clearly between the only thing which is certainly measurable in most cases. - which is (i) the geometrical albedo at full phase, or the amount of light sent earthwards at the planet's full phase. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
