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The first satellite of Jupiter
Author(s) -
Douglass A. E.
Publication year - 1898
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.18981462002
Subject(s) - jupiter (rocket family) , observatory , citation , satellite , new moon , library science , astronomy , history , computer science , physics , space exploration
Observations upon this satellite were made in Mexico from February r8 to March 28, in the Clark 24 inch refractor of this Observatory, and in Flagstaff from May r 6 to June 9, 1897. On April 4 and r8 the Grubb 15 inch refractor of the Mexican National Observatory was used. Definite markings on the first, third and fourth satellites were seen on February r8, 20 and 24 respectively; but those on the third and fourth were more easily followed and were constantly watched. Except some preliminary and routine micrometer measures of diameters, work on the first satellite was largely incidental, but in view of the approaching opposition of Jupiter it is desirable to reduce it to a form suitable for future use. The results of the observations for detail on the third satellite have been published but much material has been gathered since then, including many old drawings made before the present work was begun. Reduction of the work on the fourth satellite was commenced, but met this curious obstacle, that either this satellite revolves in onehalf of its period about Jupiter or the detail is symmetrical with respect to its axis. From the motion exhibited from day to day by the more conspicuous points of its detail the latter is judged to be the case. This result is especially mentioned because, from the recently completed reduction of observations on the first satellite, it is probable that its detail is also symmetrical with respect to its axis. Upon three nights, February 28, March 5 and 6 movement of detail upon the first satellite was followed for about two hours; it moved toward terrestrial west, indicating a direct rotation. The seeing was good on these dates and on each occasion confidence was expressed in the direct rotation thus found. On March 7 some very characteristic detail was visible but the seeing was baffling and it could not be so well located. There seemed, however, a connection between two series of drawings separated by three hours, and a rapid direct rotation was indicated. On the roth the satellite was followed for over two hours but no satisfactory result on this question was obtained, owing to the falling off in the seeing.