Comet Ikeya-Zhang

Comets in the sky are a rare joy. On average, there are only two or three comets each year that are visible to the naked eye. This year, comet Ikeya-Zhang offers the best opportunity for comet spotting since Comet Hale-Bopp passed the Earth five years ago. The comet was independently discovered on February 1, 2002 by amateur astronomers Kaoru Ikeya, in Japan and (just over an hour later) Daqing Zhang in China. By tradition, comets are named after the discoverers. This has led many amateur astronomers to scan the skies in hopes of discovering an unknown comet.

The last time this comet was seen was in 1659. This gives it an orbit of 343 years. No other returning comet has ever been recorded with a longer orbit.

Comet Ikeya-Zhang - Click for a Larger Image - Credit: D. Aguilar, Harvard-Smithsonian Center for AstrophysicsOn March 18, the comet made its closest approach to the sun. It will come within 60 million kilometres of Earth as it passes by us on April 29. The first week in April offers the best viewing opportunity. The comet's brightness will diminish throughout the remainder of the month as it begins to leave our solar system.

While it will be visible with the naked eye, binoculars will make the tail stand out very clearly. Ikeya-Zhang will be clearly visible in both the evening (western sky) and morning (eastern sky) skies this week. Check low in the western horizon early in the evening. Later, as the moon rises, the comet will be reduced in visibility. Look for a triangular smudge of light with the tip pointed towards the ground. The tail will trail trail above the comet vertically.

Comets are one of the most fascinating astronomical phenomena. They represent objects created at the same time as the solar system, some 4.5 billion years old. They are composed of rock and ice and follow very long orbits. As the comets approach the sun, it warms enough to emit gases and dust, and this forms the comet's tail.

Comets are also steeped in mythology. For centuries, they were seen as a harbinger of disaster. In medieval times, the arrival of a comet seemed to wreak havoc on the idea of a divinely created and unchanging cosmos. In 1578, A Lutheran Bishop of Magdeburg by the name of Andreas Celichius published a "Theological Reminder of the New Comet". This publication indicated that the tail of the comet was "the thick smoke of human sins, rising every day, every hour, every moment, full of stench and horror before the face of God, and becoming gradually so thick as to form a comet, with curled and plaited tresses, which at last in kindled by the hot and fiery anger of the Supreme Heavenly Judge." In 1066, Halley's comet returned over England. To the Normans who believed that it foretold the fall of a kingdom, it may have precipitated their conquest of England by William the Conquerer.