Abstract
SATURN VISIBLE THROUGH THE CASSINI DIVISION.—An interesting circular has been issued by Mr. C. T. Whitmell, of Leeds, calling attention to the possibility of this phenomenon being observed. On July 17, 1902, at 1311. G.M.T., Saturn will be in opposition to the sun, and about 7h. G.M.T. on that day the earth and sun will be equally elevated above the ring plane, their Saturnicentric declination being about 22° 26′ 17″N. Adopting Prof. Barnard's estimate of 2270 miles for the breadth of the Cassini division, and fifty miles for the thickness of the rings, Mr. Whitmell calculates that the effective opening of the division will be 820 miles, corresponding to 0″.20 in angular measure at the earth's distance. Under these conditions a line from the sun to the earth will pass through the rift in the rings to the planet, and a terrestrial observer, suitably placed, may be able to view through the rift a portion of the planet's surface lit up by the sunlight. The effect will be that, of the arc of the Cassini division crossing the planet, a small portion will appear bright instead of dark, and may almost disappear; as the albedo of Saturn is less than that. of the adjacent portions of rings A and B, however, it is likely that there will be sufficient contrast to show the phenomenon.
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Our Astronomical Column . Nature 66, 87–88 (1902). https://doi.org/10.1038/066087a0
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DOI: https://doi.org/10.1038/066087a0