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SUNGRAZING COMETS - DECEMBER 19

Above : The Great Comet of 1882

Below : A SOHO sungrazer

BRIDGEPORT, WV (S-M) - Some of the most spectacular comets ever seen have been the sungrazers. About a dozen of these monsters of the sky have appeared to the naked eye in the past 300 years.

 

It is thought that the sungrazers all began as one giant comet, which at some point in the past passed too close to the Sun and broke into pieces. No one knows how many pieces are out there. A new one could arrive at any time. When one is discovered it is said to be a Kreutz group M comet. But what these objects all have in common are their close approaches to the Sun at perihelion. Comet Peryra in 1963 came within just 60,000 miles of the Sun's surface, and most other comets in the group have approached our star to within 500,000 miles.

 

The mid-1800's was a time of great cometary activity, and four sungrazers appeared between 1843 and 1887. Comet 1843 I may hold the all-time record for the longest tail, at 200 million miles, and the Great Comet of 1882 was visible in daylight, to those who knew where to look.

 

Of the three sungrazers of the twentieth century, perhaps the most fantastic was Ikeya-Seki of 1965. The comet swept to within 307,000 miles of the Sun's surface, and shot around the Sun in just six hours. In the morning sky, the tail looked like a searchlight shining up from the horizon, and spanned a full 25 degrees. At 75 million miles long, its length was almost as great as the distance from the Sun to the Earth.

 

The 1980's saw renewed interest in sungrazers as space missions began to discover small objects. The SOLWIND instrument discovered six between 1979 and 1984, and the Solar Maximum Mission discovered at least ten between 1987 and 1989.

 

Discoveries began at a phenomenal rate with the launch of the Solar and Heliospheric Observatory, SOHO. Since 1995, it has discovered at least 900 small Kreutz sungrazers, and several hundred others which belong to new groups. Hardly a week goes by without another new discovery from SOHO. - GW