A research paper has recently appeared on arXiv (Manterola et al., 10/14/2011) suggesting that a huge comet nearly struck Earth in 1883.
José Árbol y Bonilla of Zacatecas observatory reported an unusual set of solar observations in an 1886 issue of L'Astronomie. Bonilla had an excellent reputation among astronomers, and his observatory was suitably equipped for solar observation. But Bonilla did not know what he actually observed, and neither he nor the paper's editor submit a hypothesis about what caused the strange observation.
Bonilla reported seeing, on August 12-13, 1883, over 400 small objects transit the sun's disk in less than a second each. He immediately informed observatories at Mexico City and Puebla, but they did not see the phenomena.
128 years later, Manterola et al. proposed that the objects were parts of a fragmenting comet that nearly hit the Earth. Their argument goes as follows:
- Not seeing the objects at alternate sites implies they passed closer than 65,000 kilometers.
- Assuming their own hypothesis (that the objects came from a fragmenting comet), the transit times suggest distances smaller than 10,000 km.
- The angular size of the objects sets their size at roughly 50-1000 meters, having masses from 109-1012 kg.
- On impact, each object produces an explosion of at least a few hundred megatons. Given thousands of such impacts, the result is an extinction-level event.
Manterola et al. lay out these points using visuals and equations. Because we now know much more about comentary fragmentation, Manterola was able to go back in time and come up with a hypothesis for Bonilla's observations. Whereas in Bonilla's time only a few comets that had fragmented had been observed.
Is there any reason to believe this self-referential scenario? Phil Platt of Bad Astronomy points out that fragmenting comets don't behave this way. The tightly focused stream of objects, lack of nocturnal phenomena (including a poor crop of Perseid meteors those nights), and lack of a candidate comet make this interpretation very dicey. True belief and acceptance for Manterola's argument would require more data than provided by Bonilla, so the cause of these observations remains a mystery.
- Want to learn more about the most recent discoveries by astronomers about comets? Check out this slideshow with stunning images of comets in space.