Abstract
DARK TRANSITS OF JUPITER'S FOURTH SATELLITE.—Prof. Davidson, of the U.S. Coast Survey, has communicated to the Californian Academy of Sciences some interesting notes of observations of “dark” transits of Jupiter's satellite IV. n ade by Mr. Burckhalter with a 10½-inch reflector. Mr. Burckhalter's observations on May 21, 1885, suggest the possibility that the satellite has an area of white surface and also an area of dark surface. When the satellite approached the planet it appeared bright, the white area being then the visible part; but when it had advanced some way on the disk, this white part was (on this supposition) lost in the superior brightness of the planet, and the dark area became visible. Prof. Davidson thinks it might even lead to the determination of the rotation period of the satellite if it were watched throughout the whole transit, and the different phases neted. Again, observing on June 7, 1885, Mr. Burckhalter saw the satellite as a dark spot on the edge of the north dark belt. But as soon as the satellite was clear of the planet's disk, it was noted to be north of this belt; so that it would appear from this observation also as if the satellite were divided into bright and dark areas, the south pole being the dark one. Prof. Davidson also observed the transit of June 7 with a 6.4-inch refractor, and confirms generally the appearances noted by Mr. Burckhalter.
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Our Astronomical Column . Nature 33, 466 (1886). https://doi.org/10.1038/033466a0
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DOI: https://doi.org/10.1038/033466a0