Secular and Librational Motions of the Pole.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Secular and Librational Motions of the Pole. Markowitz, William Abstract The polar motion is known to include 12- and 14- month periodic components. It has frequently been suggested that a secular component also exists, but its reality has hitherto been considered doubtful because of inhomogeneities in the observations. A method of analysis is presented which enables the polar motion to be derived from the results of the northern chain of the International Latitude Service (I. L. S.) free from the effects of these in- homogeneities. The resulting polar motion is independent of errors in the positions and proper motions of the stars observed, of changes in the observing program, and of errors in the micrometer scale value. The I. L. S. results indicate that from 1900 to 1960 polar motion had two components in addition to the 12- and 14-month terms, a progressive motion of 0'.'0032 per year along the meridian 600W, and a libration of period 24 years and coefficient 0'.'022 along the meridian 1220W-580E. These are mathematical representations of observed motions for which no physical causes are ascribed. The motions cannot be safely extrapolated into the past or future. Observations of latitude and longitude made with the photographic zenith tube (PZT) at the U. S. Naval Observatory since 1915 are in agreement with the I. L. S. results. The secular motion of the pole from 1900 to 1960 is 0'.'2. Account must be taken of the total motion of the pole in the precise determination of latitude, longitude, and time. The `north pole is moving in the general direction of eastern North America at a rate of one degree per million years. This rate is too small to account directly for the occurence of ice ages within the past 50 000 years. Publication: The Astronomical Journal Pub Date: 1960 DOI: 10.1086/108078 Bibcode: 1960AJ.....65Q.349M full text sources ADS |