This has to be one of the most interesting and disturbing things I have read in a long time. Scientists and astronomers are looking at some historical reports of a phenomenon that was observed by an astronomer in Zacatecas Mexico in 1883. The team is analyzing the data because they think what was observed by Jose Bonilla over 100 years ago may have been a very near miss of a massive comet that would have killed everything on the planet.
Bonilla counted 450 objects that were each surrounded by what is described as a kind of mist passing across the face of the sun. The astronomer published his account of the event in a French journal called L'Astronomie three years later in 1886. At the time, the editor of the journal suggested the sighting was nothing but dust on the telescope or birds. However, after reanalyzing the data available modern scientists think that what Bonilla was seeing were the remnants of a giant comet that had only recently broken up.
The recent breakup of the comet would explain the misty appearance according to the scientists. There were other observatories in the area, as close as a few hundred kilometers that didn't see what Bonilla noted. However, modern scientists explain this because of parallax. The team says if the fragments were too close to the Earth, parallax would have meant the chucks of the comet would not have been in line with the sun and viewable even for observers at nearby observatories of the time. According to the researchers, Hector Manterola at the National Autonomous University of Mexico in Mexico City and his team, the objects would have been as close as 600km to 8000km from Earth for parallax to prevent others from seeing them.
The team also estimates that the chunks would have been anywhere from 50 to 800 meters across for the parent comet to have been a billion tons or more making it roughly the size of Halley's comet. The team thinks that the comet could have been Pons-Brooks, which was seen that same year by astronomers in American. Calculations suggest there could have been 3275 objects and if they had hit Earth, it would have been an extinction event.
[via Technology Review]