1979J3: Discovery of a Previously Unknown Satellite of Jupiter

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Science  19 Jun 1981:
Vol. 212, Issue 4501, pp. 1392
DOI: 10.1126/science.212.4501.1392


During a detailed search of Voyager 1 frames for additional observations of the satellite 1979J1, two small dark spots were observed in transit in several consecutive wide-angle frames of the Jovian atmosphere. The size, spacing, and motion of these pairs of dark spots indicated that they were the images of 1979J1 and its shadow. Subsequent analysis of images spanning 6 days, however, proved that the satellite observed in these Voyager 1 frames would have been occulted by Jupiter at the times of the Voyager 2 images of 1979J1 and was, therefore, a new satellite. It was subsequently found in transit on Voyager 2 images within 13° of the Voyager 1 prediction. Its period is 7 hours 4 minutes 30 seconds ± 3 seconds, and its mean distance is 1.793 Jupiter radii (Jupiter radius = 71,400 kilometers). The observable profile appears to be roughly circular with a diameter of 40 kilometers, and the albedo is0.05, similar to Amalthea's.