RETURN OF THE COMET.

New Zealand Herald, Volume XLVII, Issue 14345, 15 April 1910, Page 7

RETURN OF THE COMET.

WHEN TO LOOK FOR IT.

VISIBLE ANY MORNING

The theory that life on earth would be endangered by the approach of Halley's comet has been combated several times, and Professor H. W. Segar, of the Auckland University College, adds the weight of Ins authority to the contention that the comet will come and go without, endangering- the ear.th or those who live on it. It lias been calculated, stated Professor Segar, while being interviewed, since, the elements of the orbit have been corrected, that if an encounter is to take place between the tail of Halley's comet and the earth, the tail of the comet would require to bo nearly 14,000,000 miles long, and its breadth, about 500,000. As a, mutter of fact this is by no means an unreasonable size for a tail to reach, so that if the tail of Halley's comet is tolerably large it is probable that the earth will pats through it. "That, kowevei," # said Professor Segar, 'means nothing except that we shall have a few more shooting stars than usual. In the tail there, certainly are various gases, .some of which would lie noxious, but the idea of their mixing with our atmosphere is absurd. Even though they reached us it would bo in such infinitesimal quantities ihaMhc effects would be negligible."

Dealing with the comet from the specliicilar standpoint, Professor Segar said it had been first photographed on this visit on August 24 of last year. I: was first seen on September 17 by Professor Barnard, Verkcs .Observatory, near Chicago. At that time it was a 15th magnitude star, and was absolutely beyond the perception of the naked eye. It was .nebulous in character, brighter in the middle than on the edge, and without a tail. By November 28 (two months latet) it was so bright that it was seen in a sky lb by a moon nearly full. Professor Barnard took observations, and the mean ol them- showed that the diameter of the head of the comet was 12,600 miles, or rather more than one and a-balf times the diameter of the earth, and three times that of Mars.

Halley's comet may be visible any morning now, even to the naked eye. Professor Segar. rose before four o'clock on a recent morning expecting to see it, but unfortunately the sky was cloudy. As the days pass the comet will rise earlier, and will become more conspicuous, but it will not be a reallv great object in the sky till next month on account of its distance .from the earth. It will reach perihelion on April 20 in New Zealand (April 19 at Home). Even then it will be over 90,000,000 miles from the earth. That day and the few succeeding davs will be the best time for observing it this month. About the 20lh it will rise about an hour and a-hall before the sun, and from 5.15 to 5.30 a.m. will be a good time for observing it. After that it will approach the sun in the sky and will become more difficult to observe till about May 19, when it is almost certain to pass across the sun's disc as seen in the sky, although it will in reality be 80,000,000 miles from the sun. At about the same time also it will be nearest to the earth. Before that dato in the mornings, and after that date in the evenings, it will reach its largest apparent dimensions. It was impossible to say, Professor Segar continued, how the comet would comparers a spectacle with its previous visits. On its last visit in 1835 the tail reached 20 degrees at its maximum, and on its previous visit it was known to reach 30 degrees. Tho tail would probably be' fairly long on this occasion. The idea was that a comet gradually died through losing substance, but this had not been absolutely proved by observation, but was a deduction from the theory of a comet. The theory, however, appeared to be borne out by the history of Halley's. From May 19 the position of the comet in the sky would change very rapidly owing to the comet and tho earth moving in approximately opposite directions and to their being so near to each other. The comet would diminish very rapidly in •apparent size and brightness, and would soon bo beyond tho range of »tho naked eye. Professor Segar intends at an early date to give a lecture on Halley's comet.