Halley and His Comet
The year is 1682. Edmund Halley, a 26 year old astronomer, recently married to Mary Tooke, has just settled in the town of Islington, England. While observing the sky he noticed a comet. Under close observation, he wondered if the comet could be the same comet that had been observed in 1607, and another that had been observed in 1531.
Studying the work of prior astronomers over the years, Halley finally reached the conclusion in 1705 that the comet was in fact the same, and that it made an orbit of the sun where it would be visible by the earth once every 76 years. He predicted that the comet would return in 1758. Although he did not live to see it, he was proven correct.
Although it was not considered a major achievement during his own time, and his other work certainly gained Edmund Halley far more fame and fortune in his own day, it is this achievement which has gained him his place in history. Since his prediction was proven correct in 1758, the comet has been known as Halley’s Comet.
Early Records of Halley’s Comet
Halley’s Comet has been seen by humans throughout time. Man has always watched the heavens, and Halley’s Comet would always have stood out to the people of the world. In fact, modern historians use descriptions of appearances of Halley’s Comet to help date events in ancient times.
Other comets are in orbit around the earth, however none of them have as short a period and the visibility of Halley’s Comet. Hale-Bopp, which made its last appearance in 1995, will not be seen again for 4200 years, while Halley’s Comet is expected back in 2062.
The first known historical record of the comet comes from the records of Chinese astronomers in the year 240 BCE. However, other historical records could indicate an appearance of the comet, going back much farther in time. The second oldest verifiable historical record comes from two clay Babylonian tablets recording its appearance in 164 BCE.
In 2004, a coin was found in Armenia which might include an image of the comet. The coin comes from the reign of Armenian king Tigranes II the Great, who reigned from 95 to 55 BCE. His reign encompassed an appearance of the comet in 87 BCE. The coming of this comet might have been immortalized on the coin, which includes a profile of King Tigranes II as well as a star symbol with a curved tail behind it.
The next appearance of the comet, in 12 BCE, coincides to a similar time as the birth of Jesus of Nazareth. Some scholars have proposed the idea that the Star of Bethlehem might actually have been Halley’s Comet making its appearance at the time of his birth. The star was most likely the inspiration of Giotto di Bondone, who had seen the comet in 1301, in his painting of the Star of Bethlehem in the Nativity in 1305.
Halley’s Comet is mentioned in the Jewish Talmud as well. 1600 years before Halley, a star is spoken of “which appears once in 70 years that makes the captains of the ships err.” This is the first reference to the idea of the comet returning, long before Halley’s observations.
Halley’s Comet During the Middle Ages
During the Middle Ages appearances of the comet were very often seen as a sign or warning. The most famous appearance of the comet during this time period came in 1066, when its arrival came shortly before King Harold’s defeat at the Battle of Hastings. Harold reportedly saw the comet as an ill omen, and the famous Bayeaux Tapestry which recounts the events of the Norman Conquest includes an image of Harold seeing the comet in the sky.
Another famous incident involving the comet came in 1456. The Pope of the day was Calixtus III, and he excommunicated the appearance of the comet, believing it to be a sign of evil omen. Europe was at that time struggling with the Ottoman Empire, which had only 3 years prior taken Constantinople and brought down the mighty Byzantine Empire.
Halley’s Comet in Recent Times
Since 1758, mankind has anticipated the return of Halley’s Comet every 76 years. Astronomers have used its appearance to study the comet and comets in general.
American writer Mark Twain understood the cycle of the comet. He was born in 1835, a year of Halley’s Comet’s appearance. 74 years later, in 1909 he said: “I came in with Halley’s Comet in 1835. It is coming again next year, and I expect to go out with it.” He fulfilled his own prophecy, dying the next year.
The comet’s last return was in 1986. Although highly anticipated, it did not come as close to earth as it had in previous appearances and combined with the increase in light pollution it was difficult for many to see. However, it did offer scientists their first chance to study a comet close up.
The Giotto Space Probe
Since Halley first determined that the appearances of comets on a regular basis every 76 years were in fact the same comet, great study has been made of it. The most recent visit of the comet came in 1986.
In anticipation of the 1986 appearance of the comet, the European Space Agency created the Giotto space probe, named after the artist Giotto di Bondone. It was designed to approach the comet, take pictures and study the composition and structure of the comet, something which had never been done at such close range before with any comet.
On March 13th, 1986, the probe passed with 600 km of the comet, and took incredibly close pictures. It found that the nucleus of the comet to be about 15 km long, and between 7 and 10 km wide. Analysis determined that the comet was about 4.5 billion years old, and it was composed primarily of dust and ice.
Halley’s Comet will return again in the year 2062. In that year, people all across the world, as they have for all of human history, will look up into the sky and be able to see the great comet flying through the stars. It is a part of the human tradition which will never pass away.