Abstract
A PAPER was read by Mr. Edmund J. Spitta, at the November meeting of the Royal Astronomical Society, of especial interest to those who have devoted their attention to Jovian phenomena. As the paper itself is a long one, being the result of over four years' work, we must refer our readers for details to the paper itself; but, speaking briefly, the author observes that since the discovery of the satellites by Galileo in 1610, astronomers have been puzzled by their discordant appearances during transit, but more especially by the fact that these phenomena do not apply equally to all the satellites, or even in some instances to the same satellite in two successive revolutions. It appears that notably the fourth—the farthest from its primary—as it approaches the disk of Jupiter, becomes rapidly and increasingly fainter until it arrives at contact. When once on the limb it shines with a moderate brilliancy for about ten or fifteen minutes, then becomes suddenly lost to view for another period of about the same duration, and lastly reappears, but as a dark spot which grows darker and darker until it equals the blackness of its own shadow on the planet. The appearance presented by the second satellite, however, is entirely different, for it seems never to have been seen otherwise than pure white during transit; whereas the first and third differ yet again from the preceding two. The former is sometimes a steel-gray, and at others a little darker, whereas the latter has been seen perfectly white, and yet so black as to be mistaken for the fourth; both appearances having been witnessed by Maraldi as far back as 1707, and that too in successive revolutions.
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On the Appearances Presented by the Satellites of Jupiter During Transit . Nature 37, 468 (1888). https://doi.org/10.1038/037468a0
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DOI: https://doi.org/10.1038/037468a0