September 12, 2010

Greeks First To Spot Halley’s Comet

A heavenly event observed by ancient Greeks may have been the earliest sighting of Halley's Comet, say researchers.

Ancient Greek writers reported a large object crashed into northern Greece between 466 and 467 BC. The writers also described a comet in the sky at the time the object fell to Earth, but this detail has received little attention, said the researchers.

Researchers report in the Journal of Cosmology that Halley's Comet would have been visible for 80 days in 466 BC.

Previously, the earliest probable sighting of the comet was in 240 BC, as recorded by Chinese astronomers.

If the new information is confirmed, the researchers will have pushed the date of the first observation of the comet back by 226 years.

The space rock that ancient authors reported fell during daylight hours and was about the size of "a wagon load," according to the ancient source. The object was described as having a "burnt color" and was a tourist attraction for more than 500 years.

Aristotle wrote about the event a century after it occurred. He said that around the same time the meteorite fell, "a comet was visible in the west."

The likely path of Halley's Comet was reconstructed by astronomer Eric Hintz and philosopher Daniel Graham, both of Brigham Young University in Provo, Utah, to see if whether it agreed with the ancient observations.

They calculated that the comet could have been visible for around 80 days between early June and late August in 466 BC.

Eric Hintz told BBC News that "it's tough going back that far in time. It's not like an eclipse, which is really predictable." He said that if the sighting in 240 BC is accepted, "this has a fairly solid possibility."

The reconstruction of the comet's path agrees with the ancient reports, which shows the comet was visible for around 75 days.

Although ancient Greeks were not as meticulous about providing astronomical information as Chinese were, they did provide important information, such as the period of visibility of the comet, said Graham and Hintz.

However, Hintz said the passing of the comet was not likely linked to the falling meteorite described around the same time. "It would be really neat if they were connected - if it was a piece of Halley's that fell. My feeling is that it was just a really cool coincidence," he added.

The researchers believe there may be accounts of even earlier sightings of comets from ancient Chinese and Babylonian records not yet brought to light.


On the Net: