Our Astronomical Column

Abstract

THE RED SPOT ON JUPITER.—This object exhibited a slackening motion during the years from 1878 to 1900. It then became decidedly accelerated, so that the rotation period, which in 1899 and 1900 was gh. 55m. 41.7s., decreased in 1901 to 9h. 55m. 40-6s., and in 1902 to 9h. 55m. 39.0s. In 1903 the spot again became retarded, and the rotation period increased to 9h. 55m. 41.0s. This retardation has now in turn given way to another acceleration of speed. In January last the longitude of the spot was 35°, whereas at the present time it is only 30°, so that the rotation period during the first six months of 1904 has been about 9h. 55m. 39.5s. It is difficult to explain these curious oscillations in velocity. Some extensive disturbances have, however, affected the south temperate region of the planet in recent years, and a large dusky patch has been visible since 1901 rotating with a rate of 9h. 55m. 18.7s., or about 22 seconds less than that of the red spot. The motion of the latter may possibly have been affected by disturbances occurring in the same latitude, but this can only be fully determined by further observations. In the meantime, both the red spot and the south temperate spot are being attentively watched as to their motions and appearances. The two objects were in conjunction in July, 1902, and June, 1904, and in the spring of 1906 the event will be repeated if the south temperate spot should remain visible until that time. As to the red spot and its surroundings, they appear to form features of remarkable permanency, and are likely to continue perceptible for an indefinite period.