NS: Ancient Greeks spotted Halley's comet

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NS: Ancient Greeks spotted Halley's comet

Post by bystander » Wed Sep 15, 2010 1:29 am

Ancient Greeks spotted Halley's comet
New Scientist | Space | Comets and Asteroids | 09 Sept 2010
A CELESTIAL event in the 5th century BC could be the earliest documented sighting of Halley's comet - and it marked a turning point in the history of astronomy.

According to ancient authors, from Aristotle onwards, a meteorite the size of a "wagonload" crashed into northern Greece sometime between 466 and 468 BC. The impact shocked the local population and the rock became a tourist attraction for 500 years.

The accounts describe a comet in the sky when the meteorite fell. This has received little attention, but the timing corresponds to an expected pass of Halley's comet, which is visible from Earth every 75 years or so.

Philosopher Daniel Graham and astronomer Eric Hintz of Brigham Young University in Provo, Utah, modelled the path that Halley's comet would have taken, and compared this with ancient descriptions of the comet (Journal of Cosmology, vol 9, p 3030). For example, the comet was said to be visible for 75 days, accompanied by winds and shooting stars, and in the western sky when the meteorite fell.

The researchers show that Halley's comet would have been visible for a maximum of 82 days between 4 June and 25 August 466 BC. From 18 July onwards, a time of year characterised in this region by strong winds, it was in the western sky. At around this time, the Earth was moving under the comet's tail, so its debris field would have made shooting stars.

None of this proves the comet's identity, but Graham says such major comet sightings are rare, so Halley must be a "strong contender". Previously, the earliest known sighting of Halley was made by Chinese astronomers in 240 BC. If Graham and Hintz are correct, the Greeks saw it three orbits and more than two centuries earlier.
First sighting of Halley’s comet pushed back two centuries
PhysOrg | Space Exploration | 13 Sept 2010
Researchers have modeled the likely path taken by Halley's comet in the 5th century BC and compared their findings to ancient Greek texts from the period. They now suggest the ancient Greeks saw the comet, which would make the sightings over two centuries earlier than previous known observations.

Chinese astronomers first described the comet in 240 BC, but in ancient Greece in 466-467 BC Greek authors described a meteor the size of a wagon that crashed into the Hellespont region of northern Greece during daylight hours, frightening the population and creating a tourist attraction that lasted five centuries. The ancient authors describe a comet in the sky at the time.

Researchers Daniel Graham, a philosopher, and Eric Hintz, an astronomer, from Brigham Young University at Provo in Utah, compared their model of the comet’s likely path with the texts describing the meteor crash. Halley’s comet would have been visible for 82 days maximum, depending on atmospheric conditions at the time, while the ancient texts say the comet was visible for 75 days.

When the meteor fell, the comet was said to be in the western sky, and according to the model comet Halley would have been visible from 4 June to 25 August in 466 BC, and would have been in the western sky from July 18th. The comet was said to be accompanied by winds and shooting stars, and in July strong winds are common in the region. If the model is correct, at this time the Earth would have been moving under the comet’s tail, and shooting stars could have been created from its debris field.
Halley's Comet Was Spotted By Ancient Greeks
Space.com | Science News | 14 Sept 2010
The ancient Greeks probably saw Halley's comet streak past in 466 B.C., pushing the earliest documented observation of the comet back by more than 200 years, a new study has found.

And a meteorite struck northern Greece while the comet was burning in the sky, shaking up the ancients' understanding of the cosmos, the research shows.

"It looks like a promising account of the comet," said Daniel Graham, a professor of philosophy at Brigham Young University, who was lead author of the study. "The evidence is all very consistent with Halley's."
An Ancient Greek Sighting of Halley's Comet?
  • Journal of Cosmology 9 2130 (July 2010) DW Graham, E Hintz

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