The Bonilla Plates

The archive's telling says an astronomer in Mexico photographed hundreds of spindle-shaped craft flying in formation between his telescope and the Sun. The astronomer was José Árbol y Bonilla, director of the observatory at Zacatecas. On 12 and 13 August 1883 he was observing the Sun when dark objects began to cross its disc. By his account several hundred of them passed over about a day and a half. He photographed them on wet plates.

The vivid version in our telling is not Bonilla's. The phrase about spindle-shaped craft in formation comes from Frank Edwards, who framed the case that way in 1966. Bonilla's own report describes dark objects crossing the Sun.

What is on the record

The observation is a matter of published scientific record. Bonilla wrote to the French astronomer Camille Flammarion, and his report appeared in the journal L'Astronomie on 1 January 1886 with the photographs behind it.

Two explanations stand in the record. Flammarion and others proposed birds, insects or dust close to the telescope. A paper published in 2011 by Manterola, Ramos Lara and Cordero argued instead for fragments of a comet passing close to Earth. Neither has displaced the other, and the archive holds neither the 1886 article nor the 2011 paper.

Two claimants are on file, Bonilla and his colleagues, and the colleagues are a group named only in our telling. The published observation is Bonilla's alone: one trained observer and his plates.

Why it sits where it does

The L3 grade comes from those two entries for one connected event. Both are drawn from one video, and one of them is an unnamed group. The case's real weight lies outside our holdings, in a journal report and a set of photographic plates that astronomers have returned to for well over a century. What crossed the Sun over Zacatecas is not resolved here.