McKeesport, Pennsylvania, USA — 11 August 1878
Planetoid passing in front of Jupiter
Two amateur astronomers, Messrs. Gemill and Wampler, observed an unusual celestial object using a 5-inch telescope. At 10:05 P.M. they noticed a dark round spot on the eastern margin of the disc of Jupiter. It moved west, just above the northern belt, parallel with the planet’s equator, and passed off the face at 1:24 A.M. on 12 August, having crossed the disk in 3 hours and 19 minutes. The object appeared as a perfect sphere, much larger than any of Jupiter’s satellites. It was well-defined and sharp, most intensely black. The observers commented “it was neither a satellite nor the shadow of one, because all four satellites were in full view all the time.” Note: Jupiter has other satellites that were unknown at the time, but they are much smaller than the four satellites in question, and could not explain the effect observed.
Source: The Indiana Progress (Indiana, Pennsylvania), 22 August 1878. 499. Case: W450