Growth of a Tail

Last week a new comet hove into naked-eye view--that is, into the view of people with good eyes. Most observers found it better to look at through 8-power binoculars. A faint feather, the comet is crawling down the western sky, after dusk, toward the constellation of the Eagle (Aquila). It will get brighter this week and next. Toward the middle of January, if it develops as astronomers hope, Cunningham's comet should be the brightest since Halley's great comet of 1910.

Discovered on photographic plates last September by Leland Cunningham of Harvard Observatory, the comet last week was about 100,000,000 miles from earth, about the same distance from the sun. On Jan. 10 it comes closest to earth (54,000,000 miles), on Jan. 16 closest to the sun (33,000,000 miles). By then, on account of the sun's dazzling proximity, the show will be over.

Astronomers cannot say in advance just how bright a comet will be, because they do not know how much tail it will acquire when it approaches the sun--for the tail of a comet consists of very thin material driven away from the head by pressure of solar radiation. So far, according to Harvard, the Cunningham's tail is developing "very, very nicely." It was more than 1,600,000 miles long last week and still growing. It is possible that the earth will pass through the tail. If so, no harm will be done. The earth probably swept through the tail of Halley's comet in 1910 and no one but astronomers was the wiser.

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