Comet Ikeya-Zhang Climbs to Prominence

April 8 Update Comet Ikeya-Zhang is fading quickly, so you need at least binoculars to find it. The comet moves from Andromeda to Cassiopeia early this week, and will slide along one "side" of Cassiopeia's W-shaped pattern over the next few days. It's best seen in the northeast beginning a couple of hours before sunrise. April 10-15 Finder Chart April 3-5 Finder Chart March 24-26 Finder Chart March 14-20 Finder Chart

A recently discovered comet should put on a good show during March and April as it loops around the Sun and heads back into deep space. It could brighten enough to see with the unaided eye in mid-March, and should remain visible through binoculars for several weeks. It appears in the evening sky in March, then does double duty in the evening and morning sky during April.

The comet as seen from McDonald Observatory. (Tony Farnham)

The comet is called C/2002 C1 (Ikeya-Zhang). The code number indicates its discovery sequence, while the names come from the two amateur astronomers who discovered the comet almost simultaneously on February 1 -- Kaoru Ikeya of Japan, and Daqing Zhang of China.

After plotting the comet's path for several weeks, astronomers calculated that it orbits the Sun once every 367 years. It will pass closest to the Sun on March 18, at a distance of 47 million miles (76 million km) -- half the distance from Earth to the Sun.

A comet is a ball of frozen water and gases mixed with rock. As it's warmed by the Sun, some of the ice vaporizes and spews into space. This process releases small particles of rock, too. The material spreads out to form a coma -- a large, glowing cloud around the comet. The Sun pushes some of the coma material outward, creating a tail that can span millions of miles.

The coma and tail are what make a comet so bright, but the process that creates them is difficult to predict. A few weeks after its discovery, Ikeya-Zhang suddenly flared to several times its predicted brightness. The comet may continue to brighten faster than expected, or it may fade again after releasing big outbursts of gas and dust.

Watching the Comet
Based on current predictions, the comet should reach its peak brightness in middle to late March, when it should be bright enough to see with the unaided eye from dark skywatching locations. City dwellers probably will need binoculars to find the comet.

In mid-March, Ikeya-Zhang stands well up in the west as darkness falls, in the constellation Pisces. It sets about three hours after the Sun. As the month progresses, it will move farther north and drop a little lower in the sky each evening. Around March 27 it passes just a few degrees from the spiral galaxy M33. And in early April it crosses just above M31, the great Andromeda galaxy.

Ikeya-Zhang moves into view in the morning sky around the first of April, while remaining visible in the evening. It will slide past the W-shaped constellation Cassiopeia around April 10-15, and will become "circumpolar" -- it will never set (although it will be visible only during the nighttime hours). But the comet will be fading quickly as it moves farther from the Sun.

Ikeya-Zhang will pass closest to Earth on April 28, at a distance of about 38 million miles (61 million km).

We have provided several charts to help you find the comet at different times, and will post updates to this page.

Links
Minor Planets Center
Technical details on the comet's location

Gary Kronk's Cometography
Photographs plus a detailed chronology

Jet Propulsion Laboratory Comet Page
Images and finder's charts