The Bonilla Observation: 447 Objects Across the Sun, Zacatecas 1883

The observatory on Cerro de la Bufa, above the city of Zacatecas, opened on 6 December 1882. It was called the first major astronomical observatory in Mexico to be opened outside of Mexico City. Its director was José Árbol y Bonilla, born in Zacatecas in 1853. A topographical and civil engineer by training. In 1879 he had studied celestial photography at the Paris Observatory. He was a member of the Flammarion Scientific Society of Paris.

August 12, 1883. Bonilla was preparing to observe the Sun, watching its sunspot activity. Then a stream of small bodies began to cross the solar disc.

He described them as fuzzy. Misty. "These objects were surrounded by a mist and left behind a similar misty trace." Against the Sun they looked dark. Outside of it, bright. Many had dark tails. Each one crossed the face of the Sun in about a third of a second to one second.

They kept coming. More than 300 on the first day alone. The observation ran on into August 13. Across roughly three and a half hours at the telescope, Bonilla counted 447 objects, an average of 131 an hour. He captured them on wet collodion plates, with an exposure of 1/100 second. One plate became famous. An elongated dark body, hazy at the edges, silhouetted against the Sun.

Bonilla telegraphed the observatories in Mexico City and Puebla. They saw nothing. He wrote up what he had seen without offering a hypothesis. His article, "Passage sur le disque solaire d'un essaim de corpuscules, vu à l'Observatoire de Zacatecas (Mexique)," appeared in L'Astronomie, vol. 4, in 1885, though many accounts date it to 1 January 1886. The journal's founder, Camille Flammarion, could not reach a definitive conclusion. He suspected birds, insects or dust in front of the telescope. Later writers suggested high flying geese, naming the greater white-fronted goose, Anser albifrons.

In October 2011 three researchers at UNAM, Héctor Javier Durand Manterola, María de la Paz Ramos Lara and Guadalupe Cordero, offered another idea. A comet breaking apart very close to Earth. Because Mexico City and Puebla saw nothing, they argued, the objects must have been near. Their estimate placed them 538 to 8,062 km above the planet, 46 to 795 m wide. Scaled to a full pass, they estimated 3,275 fragments. "If they had collided with Earth we would have had 3275 Tunguska events in two days, probably an extinction event."

Not everyone was persuaded. Jon Voisey at Universe Today noted there was no unusual meteor shower. Of 186 meteors recorded on 11 August 1883, 157 were Perseids. Normal. He called the hypothesis "plausible, but generally unconvincing." Nobody else reported the objects. The paper remained a preprint, a hypothesis rather than an identification.

The 2011 paper set off a wave of coverage, from MIT Technology Review to Gizmodo and Wired UK. The Bonilla plate is still widely called the first photograph of a UFO. Kevin Randle revisited the case on his blog in 2015. In February 2026 Mexico News Daily told the story again.

One man. One telescope. Hundreds of misty shadows crossing the Sun. More than a century later, what José Bonilla saw that August remains an open question.