Amateur astronomers throughout the Northern Hemisphere have marked
Thursday, April 4th, on their calendars. That evening, weather permitting,
they’ll be looking low in the northwest after sunset to spot a bright comet
very near the famous Andromeda Galaxy. The comet, which was discovered on
February 1st, is named Ikeya-Zhang [pronounced “ee-KAY-uh JONG”] for the
two keen-eyed skygazers who first spotted it.

Remarkably, both the comet and the galaxy are visible to the unaided eye —
at least for anyone with clear, dark skies far from the pall of city
lights. The view through binoculars or a small telescope should be
especially rewarding, as these two celestial spectacles crowd into the same
field of view. According to SKY & TELESCOPE magazine, on that evening the
comet passes within 1.5 degrees of the galaxy’s center. Comet Ikeya-Zhang
will then be 82 million kilometers (51 million miles) from Earth, while the
Andromeda Galaxy lies 300 billion times farther away (2.5 million

Even though it passed closest to the Sun on March 18th, Comet Ikeya-Zhang
has remained steady in brightness for the past two weeks, delighting
skywatchers with its starlike nucleus and delicate, wispy tail. “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.)

Comet Ikeya-Zhang will be nearest to Earth, 60 million km (38 million
miles) away, on April 29th. It remains visible to observers in the Northern
Hemisphere throughout this period, though it won’t become well separated
from the Sun 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,
Japan) and Daqing Zhang (Kaifeng, Henan province, China), who spotted the
comet on February 1st using their backyard telescopes. Within days of the
discovery, astronomers noticed similarities between the orbital path of
Ikeya-Zhang (known formally as C/2002 C1) and that of other comets observed
in 1532 and 1661. Calculations now strongly suggest this is the object seen
in 1661, which is making its first return visit to the inner solar system
in 341 years. No other comet with such a long period has been witnessed on
successive orbits around the Sun. (Halley’s Comet, by comparison, comes our
way every 76 years or so.)

For more details about the discovery and appearance of Comet Ikeya-Zhang,
including a table of astronomical coordinates for its exact location, see

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SKY & TELESCOPE is making several illustrations available to the news
media. Permission is granted for one-time, nonexclusive use in print and
broadcast media, as long as appropriate credits are included. These
illustrations, along with an online version of this release, are available
on the magazine’s Web site at

* color photograph of Comet Ikeya-Zhang, taken on March 3rd, showing a
wispy blue-tinged tail roughly 4 degrees long.

* black-and-white photograph of Comet Ikeya-Zhang, taken on March 21st,
showing a striking tail laced with delicate streamers.

* color illustration of Comet Ikeya-Zhang’s location among the stars in the
western evening sky for the week of April 1-7.

* color illustration of Comet Ikeya-Zhang’s trajectory among the planets of
the inner solar system during March and April.