Sun-Grazing Comets

Press, Volume CIV, Issue 30895, 30 October 1965, Page 18

Sun-Grazing Comets

The brilliant comet IkeyaSeki aroused considerable interest during October, when it was visible in broad daylight. This comet is apparently one of a small family of such objects, usually referred to as “sun-grazing comets” because of the closeness with which they approach the sun. The family includes at least 22 comets, of which nine have been really magnificent objects. Several have been visible in daylight. They all appeal to follow somewhat similar paths around the sun, passing very close to it, and appear to come from the same direction in space. These similarities have given rise to some interesting theories as to their origin. One theory suggests that originally there was only a single comet, which over thousands of years has broken up into fragments, each of which has steadily drifted apart from the others. While comets have been observed to break up, there is little hope of proving this theory.

One of the most striking members of this group was the comet of 1843, which emerged apparently undisturbed after passing through the outer atmosphere of the sun, known as the corona. At one point this comet was even closer to the sun than comet Ikeya-Seki, passing only 81,000 miles from the sun. Four days later it was visible in daylight and had a magnificent tail that was 200 million miles long. That is more than twice the distance from the sun to the earth. At the Mount John University Observatory there is an interesting link with some famous comets. The 8 inch refractor was originally built for John Tebbutt. a famous Australian amateur astronomer. He was the discoverer of several comets, including that known as the great comet 1861 (II). Later this telescope, before being purchased by the writer, was used by Walter Gale, another noted Australian astronomer, who also discovered a number of comets.