GLORY OF THE STARS

New Zealand Herald, Volume LXXIII, Issue 22538, 1 October 1936, Page 8

GLORY OF THE STARS

HEAVENS IN OCTOBER INTERESTING MINOR PLANET CLOSE APPROACH TO EARTH BY CRUX AUSTBALI9 In addition to the nine major planets of the solar system there are more than 1000 minor planets or asteroids, whose numbers are being added to at the rate of 100 a year by new discoveries. For many years the belief was general that these minute bodies, only a few miles in diameter, lay only between the orbits of Mars and Jupiter, and Eros, one of these objects, had an especial interest for astronomers in that; its orbit at times came considerably inside that of Mars, making it on such occasions the nearest body to the Earth except our satellite, the Moon. In 1931, however, JCros was dethroned from its proud position. On March 12 of that year n tiny asteroid was discovered which at its nearest is only 10,(XX),000 miles from the Earth. Only five weeks later another asteroid was found which approached even closer to the Earthj'?being only 3,000.000 miles distant at the time of its discovery. Ifc will approach within 2,000,000 miles in 1940.

Discovery of Auteros ""-'•j On February 12 of this year a fur-"' ther tiny asteroid was discovered with an orbit so eccentric th:.t it resembles a comet rather than an asteroid, the vast majority of which possess almost circular orbits. On February 7 the new planet was not more than 1,500,000 miles from the Earth anil when it was discovered it was 8,000,000 miles distant and receding at a rate of 1,250,000 miles a day. As the new body, which has been called Anteros, travels in toward the Sun; almost to Mercury's place, it passes within 1,000,000 miles of Venus.' orbit, while its approach to that of Mars on its outward trip will be slightly less. Although Anteros' period is only 2.55 yeftrs a thousand years will elapse before another close appioach to the Earth occurs? if the preliminary orbits i deduced for the asteroid are .correct. Dr. Henry Russell, in a recent issue of Scientific American, speculates on the possibility of the Earth Jbeing strnck by Anteros. "When we <|eflect that a projectile weighing perhaps 1,000,000,000 tons, and moving more ' than 20 miles a second, got by the Earth, nearer than anything ever known before to astronomers, without being seen until it was well past, one starts thinking," he sajs. Possibility of Collision

In examining the relative orbits of Anteros and the Earth, however, Dr. Russell finds that there is only about one chance in 50,000 of an encounter taking place, or about one chance lin 125,000 yeam. During that time the varying gravitational pulls of the major planets may so alter th< orbit of the asteroid that .an encounter will never eventuate —or'then again the changes might be such -as would precipitate a collision in a much shopier time. If such a body were observed over a good interval of time and its orbit precisely determined, i;uch is the present standard of ,computational astronomy that it would be possible to predict the various alterations to its orbit caused by planetary influence"), so that the place and time of such a disaster could be predicted accurately in advance, and Dr., Russell suggests the systematic evacuation of half a continent to escape the peril. " But the chance of such a thing is so excessively small," he adds, " that kstronomers could not honestly ask for the endowment of an extensive asteroid patrol to forewarn us.*' Phenomena For October The Sun will he in the constellation Virgo throughout the month, passing into Libra on the 31st. Its noon altitude at Auckland will ir crease during the month from 56- dea. to 67 cleg. The Moon will be in conjunction with the various planets as follows: —Mars, 12th, 3 p.m.; Mercury, 14th, 1 p.m.; Venus, 18th, 4 p.m.; Jupiter, 20th, 11 p.m.; Saturn, 27th, 3 p.m. The inferior planet Mercury, which was visible throughout la:st month, will be in conjunction with the Sun, and therefore invisible, to-cay. By the middle of the month, however, it will be visible in ;the morning sky, .attaining its greatest elongation from tii& Suia on the 16th. Venus s now .beeoniing a prominent object i;i the western evening sky shortly after sunset. Mars is in the.morning sky, but is not a prominent object owing to its great distance from the Earth, Jupiter remains a subject worthy of observation in the evenings, setting about 9.30. Saturn, is above the horizon most of the night, setting about 3 a.m. Its wonderful ring system is now presented nearly edgewise to our vision, and it is therefore robbed of some of its glamour as a telescopic object. v