Surprise Comet Streaks Into Solar System

National Geographic News
December 19, 2002

Astronomers have received a holiday bonanza in the form of the arrival of a previously unknown comet that has entered our part of the solar system.

The comet was discovered by a Japanese amateur astronomer, Tetuo Kudo, early on the morning of December 14, said Clay Sherrod, an astronomer with the Arkansas Sky laboratory.

"In mid- to late-January the comet will be favorably placed for early risers in the northern hemisphere and will probably be visible to the naked eye, at least toward the end of that month," Sherrod said. "Certainly binoculars will aid in spotting the comet and exposing any tail that it might show."

Named Kudo-Fujikawa (and officially designated C/2002 X5), the comet is moving east-southeast through the constellation Hercules.

"The comet is a swift-moving object and currently is easily visible in the northeastern skies during pre-dawn hours, showing a pretty distinct tail and large coma (head or halo, caused by the emanation of gases and other materials as the comet warms up on its approach to the sun). The tail appears to be slightly less than one-half degree and several spikes in this tail have been recorded (on December 15) by imagers in New Mexico," Sherrod said.

The jury is still out regarding just what kind of show Kudo-Fujikawa would provide Earth-based viewers when it is closest to the sun, but there is a prospect that it would be a "textbook comet," Sherrod said. "However, the visibility during its greatest brilliance…will be greatly hampered because of the comet's angle of approach to the sun and the Earth-sun-comet positioning during that period."

Towards the end of January, the comet will be approaching the sun and swinging behind it from Earth's vantage point, thus getting lower and lower each successive morning into early February.

"In February the comet will be more favorably placed for observers in the southern hemisphere, and there are some estimates that suggest that the comet could attain a brightness equal to the bright planet Venus (a magnitude of less than 4)," Sherrod said.

Magnitude is a measure of brightness used by astronomers. The lower the magnitude value of an object, the brighter that object is.Objects that shine with a magnitude of less than 6 are usually visible with the naked eye. Kudo-Fujikawa is currently being seen at a magnitude of between 7 and 8.

Much of what Earth will be able to see of Kudo-Fujikawa is contingent on the activity that occurs when it is closest to its pass by the sun (perihelion) on January 28, 2003, Sherrod said. At that point it will be only 16 million miles (25 million kilometers) from the sun. The average distance of the Earth from the sun is 93 million miles (150 million kilometers).

"The retrograde orbit (meaning the comet is coming in at an opposite direction in relation to the orbits of the primary planets) of this comet and its close pass from the sun at that time have suggested to many, myself included, that the comet might potentially break up from solar radiation and solar wind. If this does indeed occur, then we might expect more volatile activity from this object than if it passes perihelion totally intact and unscathed.

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