The Comet Ikeya Zhang or C/2002 C1,

by Andy Wagner (Former Member)

With the return of Comet Ikeya-Zhang back into the night sky of the northern hemisphere astronomers are pondering how bright the comet will become. There are two ways in which a comet brightens as it approaches the sun. Usually as a comet gets closer to the sun its brightness increases. Every time the comet halves its distance to the sun its brightness increases by a factor of sixteen. This trend continues until it reaches the closest point in its orbit to the sun, or perihelion. At this point the comet starts travelling away from the sun and dims in the same manner as it brightened. The second method a comet brightens is similar except once the comet travels away from perihelion it continues to grow in radiance. Halley’s comet is an example of a comet that continues to get brighter as it recedes from perihelion. If Ikeya-Zhang is a comet of the first type then the comet is already diminishing. However, if it is of the second type it may continue to brighten for up to two weeks.

Ikeya-Zhang was discovered on February 1 by Kaoru Ikeya, and later in the day by Daqing Zhang. Kaoru Ikeya is also the discoverer or co-discoverer of six other comets. After the orbit of the comet had been analyzed the Smithsonian Astrophysical Observatory found that Ikeya-Zhang was the reappearance of a comet that had previously been observed in 1661. Ikeya-Zhang was found to have a period (the time it takes an object to orbit the sun) of 367.17 years. This period is the longest one on record for a comet.

Astronomers are anticipating excellent viewing opportunities on April 4th as the comet passes through the Andromeda Galaxy (M31). For people that are interested in seeing the comet it is predicted that the comet will reach peak brightness or magnitude between April 2nd and the 8th. However other astronomers predict that the best sighting time period may come toward the end of April as the comet moves through, Cassiopeia, Cepheus, and Draco. Look for the comet about an hour before sunrise in the northeast. Grab a pair of binoculars or a telescope and check it out!

Information for this summary was taken from Comet Ikeya-Zhang at its Brightest? by John E. Bortle

Submitted Spring 2002

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Archived Articles

Mushrooms in My Yard Last Autumn - April 27, 2002
The Earth's Disappearing Night - Spring 2002
The Comet Ikeya-Zhang - Spring 2002

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