Comet Ikeya-Zhang (C/2002 C1)

Close-up of the head of Comet Ikeya-Zhang
on March 30, 2002, showing the shell
structure in the coma. CCD image copyright
2002 Gianluca Masi, used by permission.
For more of Gianluca's astrophotos, see
www.bellatrixobservatory.org

On February 1, 2002, Kaoru Ikeya of Mori, Shizuoka, Japan and DaQing Zhang of Henan Province, China independently discovered a ninth-magnitude comet. Apart from being notable as an amateur discovery in an age in which automated sky surveys such as LINEAR, BATTERS, NEAT, Spacewatch, and LONEOS are finding most comets while they are still too faint for amateurs to have a shot at them, it was also noteworthy because of the identity of its discoverers. Kaoru Ikeya had found five comets in the mid-1960s, including the spectacular Kreutz sungrazer Ikeya-Seki (1965 S1), but went through a 35-year comet-finding drought before co-discovering Ikeya-Zhang. DaQing Zhang became the first modern Chinese amateur to discover a comet, though many of the earliest surviving cometary records are from Chinese accounts. (After I found my first SOHO comet, C/2002 C4, on February 10, 2002, I got an e-mail from Chinese comet hunter XingMing Zhou. I mentioned the co-discovery of Ikeya-Zhang by his countryman, and he wrote that the two of them are friends, and although it took DaQing 700 hours to find Ikeya-Zhang, XingMing has searched the skies for comets for over 1600 hours without success. XingMing has done better in the SOHO world, having found 25 sungrazers as of Dec. 12, 2002, including the two brightest ones discovered since I started monitoring the site in June 2001.) Update: XingMing Zhou was tragically killed in an accident in August 2004.

The comet brightened rapidly; three weeks after discovery, it was approaching naked-eye visibility (for those with dark skies, at least). There was some speculation that it was a return of a brilliant comet seen in 1532 (which briefly fueled expectations of a grand showing for Ikeya-Zhang), but further refinement of Ikeya-Zhang’s orbit gave it a period of around 340 years—actually a return of Comet 1662 C1, with previous likely appearances noted in Oriental records of April 1273 and (perhaps) February 877. This makes it the comet with the longest period that is known to have been observed at more than one return. (Brian Marsden has theorized that the great Kreutz sungrazers of 1882 and 1965 are fragments of the daylight comet of 1106, and that the Great Comet of 1843—also a Kreutz sungrazer— may have been a piece of the brilliant comet seen in 373-372 BC. However, the orbits of the earlier comets—both of which were seen to have split in two—are not well enough known to be able to confirm this.)

I looked for “Izzy,” as I’ve heard Ikeya-Zhang occasionally called, several times in late February, but was thwarted by lack of anything resembling an observing site in my Queens neighborhood. It wasn’t until March 1 that I got to see Ikeya-Zhang, from Ivoryton, Connecticut. Each year, the first weekend in March, I attend a retreat there. Twice before, notable comets (Hyakutake and Hale-Bopp) had been in the sky the weekends I’d visited Ivoryton, but each time the weather didn’t cooperate. On this Friday night, though, the sky was beautifully clear. I walked to an open area (actually, the top of an earthen dam) that offered a view to the west, of Aries where Ikeya-Zhang then resided. Some stray light interfered, but the comet was easy in my 9x63 binoculars. I described it as rather bright (it was then perhaps magnitude 5.5), quite condensed, and asymmetrical (“bottom-heavy”), with a hint of a tail.

I saw Ikeya-Zhang twice from New York City, once from Prospect Park in Brooklyn, and once from Central Park. It was bright in binoculars, with a slightly bulbous head and distinct tail. From Prospect Park I saw it in twilight; it soon got caught in a cloud bank from which it never fully emerged. The Central Park sighting was after a meeting of the Observers Group of the Amateur Astronomers Association of New York in which I’d done a presentation on my first SOHO comet discovery. A group of us walked over to the park and set up scopes and binoculars; I had brought my 9x63s. I couldn’t see “Izzy” with the naked eye, but it was splendid in binoculars. I’d seen it described in a newsgroup as looking “like a Q-tip caught in a blast furnace,” which seemed an apt description. A number of passers-by stopped to have a look. The brighter winter stars glittered above the park. To the south, Orion stood undimmed amid the twin beams of the Tribute in Light, which resembled a double ion tail of a huge comet. (Some local astronomers were concerned that the Tribute—particularly if made permanent—would be anathema to efforts to reduce sky glare in Manhattan, but it did not bother me. For one thing, in designing a fitting World Trade Center memorial, preserving a dark sky will not be the paramount issue, and one beacon—however powerful—is not going to turn the sky bright by itself. It’s the other umpteen gigawatts of light being pumped skyward that's the real problem.)

I never saw the comet from a truly dark sky when it was near its peak. It became, for most observers, the best comet since Hale-Bopp, peaking at nearly third magnitude and with a tail greater than 5 degrees in length. Several observers described it as looking like a miniature Comet Hyakutake—a fitting celestial memorial for Yuji Hyakutake, the renowned Japanese comet hunter who died on April 10 at age 51 of a heart attack triggered by an aortic aneurysm. I went upstate in mid-April, but it rained all weekend. I had another chance on May 18; by then the comet looked rather globular, had faded below naked-eye visibility, and was not far from M13. It was one of the first marks for my new 127mm Maksutov-Cassegrain telescope. I made one more marginal sighting in mid-June, when the comet was rapidly fading and becoming more diffuse.

E-mail to tonyhoffman [at] earthlink [dot] net