Caption: Gerald Rhemann of Vienna, Austria, recorded Comet Ikeya-Zhang on the evening of March 3rd with a 7.5-inch (190-mm) f/2.3 Schmidt camera. In this two-image composite, the comet displays a wispy tail roughly 4¡ long. The blue color is due to gas ionized by sunlight after being released from the icy nucleus (far right). North is up. Click on the image for a high-resolution, publication-quality version.Ê© 2002 Gerald Rhemann, courtesy Sky & Telescope
A comet discovered last month by amateur astronomers is making its first
pass through the inner solar system in nearly 3-1/2 centuries. Named
Ikeya-Zhang [pronounced “ee-KAY-uh JONG”] for the two keen-eyed skygazers
who first spotted it, this cosmic interloper can be seen low in the west,
not far above the horizon, as soon as it gets dark.
According to SKY & TELESCOPE magazine, the comet is now bright enough to be
seen with the unaided eye from very dark sites free of any light pollution.
Binoculars show a bright, starlike nucleus surrounded by a small, faint
cloud, or coma. A delicate, wispy tail has been seen pointing away from the
Sun, and in time-exposure photographs the tail is already a few degrees
long. The comet’s nucleus appears to be releasing more gas than dust, which
is giving the coma and tail a slight bluish cast that is especially
noticeable in photographs.
Since Comet Ikeya-Zhang is now moving closer to both the Sun and Earth, it
should become several times more obvious by the time its brightness peaks
in late March. “Based on its track record thus far,” notes SKY & TELESCOPE
senior editor Roger W. Sinnott, “Comet Ikeya-Zhang stands to be the best
comet for northern skygazers since 1997,” when Comet Hale-Bopp put on a
command performance. (However, Ikeya-Zhang will not get as bright as
Hale-Bopp did.)
The comet will be closest to the Sun, 76 million kilometers (47 million
miles, or about half the Sun-Earth distance) on March 18th. It comes
nearest to Earth, 60 million km (38 million miles) away, on April 30th. The
comet remains visible to observers in the Northern Hemisphere throughout
this period, though it won’t become well separated from the Sun in the
evening sky until mid-April, when it is best seen before dawn. In late
April it glides to within 29 degrees of Polaris, the North Star, and
remains above the horizon all night for most of the United States and all
of Canada and Europe.
Credit for the discovery goes to Kaoru Ikeya (Mori, Shizuoka prefecture, http://SkyandTelescope.com/observing/objects/comets/article_477_1.asp
Japan) and Daqing Zhang (Kaifeng, Henan province, China), who spotted the
comet on February 1st using their backyard telescopes. At the time it
equaled the brightness of an 8-1/2-magnitude star, about 10 times fainter
than is discernible to the unaided eye. “Ikeya and Zhang were lucky,”
Sinnott notes. “Today most comets are found by automated professional
surveys months before they can be seen in small telescopes.”
including a table of astronomical coordinates for its exact location, see:
