Comet Halley

Comet Halley has had a great influence on astronomy for a number of reasons. It is a periodic comet with an orbit that brings it back to the vicinity of the earth every 74 - 80 years (the variation is due to small effects on the orbit by the outer planets).

isawhalleys.jpg (33516 bytes) This period is short enough, and the comet is dramatic enough, that humans retained a "corporate memory" of the multiple visits.

(rubber stamp by Rick Geary,

Armed with Newton's Laws and accurate measurements from a series of visits, including ones by Kepler, Edmund Halley was able to determine the orbit of the comet and connect its many sightings over history to return visits of a single object. Below, we summarize the last thousand years of returns of the comet.

bayeux.jpg (46132 bytes) Bayeux Tapestry, 1066: the comet appeared at the battle of Hastings and was thought to be a bad omen. King Harald II of England died in the battle, and the French army went on to conquer England. (from J. Paul Getty Trust, Space Art through the Ages,
halley1145.jpg (13008 bytes) 1145: Drawing of the comet in a book written in Canterbury, England.

koreanobs.jpg (65053 bytes) 1222: The orbital circumstances were relatively unfavorable for a dramatic show at earth. Korean observers reported the comet was visible during the daylight hours on September 9th (probably during twilight only). The comet may have been observed from Ch'omsongdae Obsservatory, built in the mid-7th century and the oldest surviving astronomical facility in Asia. (from
halleygiotto.jpg (65905 bytes) 1301: The appearance of the comet inspired the great late-medieval artist Giotto to use it as the "Star of Bethlehem" in his Christmas scene in the Capella degli Scrovegni, Padova, Italy.
cometschinese.gif (11146 bytes) 1378: Sightings of this return were the first in the series that convinced Halley that the appearances were periodic. Chinese observers reported cloudy weather from October 11 until Nov. 9, at which time the comet had passed behind the sun. These forms of comet with astrological interpretations date from much earlier Chinese records.
constantinople.jpg (28919 bytes) 1456: Halley's comet made its appearance just three years after the fall of Constantinople in 1453 - prior to that date, the city had been the religious and economic center of Christianity. The Pope of that period, Calixtus III, solemnly ``decreed several days of prayer for the averting of the wrath of God, that whatever calamity impended might be turned from the Christians and against the Turks.'' Then, too, was incorporated into a litany the plea, ``From the Turk and the comet, good Lord, deliver us.''


halley1531.jpg (109871 bytes) 1531: Peter Apian demonstrates diagrammatically how the tail of the comet always points directly away from the sun (he was the first to note this phenomena), showing both the comets position in the sky (including its approximate position along the ecliptic) and the sun's position on the ecliptic below the horizon (and thus invisible to the observer!). He also illustrates how a cross-staff is used to determine the angle between a celestial object such as a comet and a bright star (Cauda Leonis).



lower_william.jpg (40720 bytes) 1607: Good observations by Kepler, and the English astronomers Thomas Harriot and William Lower, provided the accurate data that Halley needed to predict the orbit and determine that the comet was periodic. Harriot and Lower were pioneers in using telescopes for astronomy, having done so at the same time as Galileo did. However, since they did not publish anything about their observations, the credit has gone almost entirely to Galileo.


halley1680.gif (3593 bytes)comet1680.jpg (18310 bytes) 1682: This painting (by Atlas van Stolk) of a beautiful comet with a long, golden tale, reflects a more positive interest people began to have about comets. However, the flyer to the far left shows that superstitions had not died out that much.,

halley1759.jpg (44261 bytes) 1759: This Korean record of Comet Halley was made during the comet’s first predicted return in 1759 AD. The Korean astronomers have been recording the appearance of comets and other unusual celestial objects for more than 3000 years. (Courtesy of Il-Seong Na, Yonsei University, Seoul.)


halley_1835.jpg (43517 bytes) 1835: Following the return of Comet Halley in 1835, which he had occasion to observe, Bessel developed the "Physical Theory of Comets," published 1836, stating that comets are mainly consisted of volatile matter.


cometplate.gif (246472 bytes) 1910: And here is a Royal Delft plate celebrating the return in this year.


giotto_h.jpg (69352 bytes) 1986: The European Space Agency sent a spacecraft to investigate the comet. Here is a picture of the nucleus; it is about 16 x 8 x 8 km in size, and the picture shows clearly the gas streaming away as the ices in the nucleus are melted and evaporated by the heat of the sun. (from ESA, APOD,