METEOR SHOWER

Evening Post, Volume CXXVIII, Issue 26, 31 July 1939, Page 10

METEOR SHOWER

A POSSIBILITY BUT NO CERTAINTY SOME FAMOUS DISPLAYS Possibly on Friday night next, August 4, a meteor shower will be visible in this part of the world. There may be only a few meteors to be seen, or there may be a brilliant display of celestial fireworks. Quite possibly, on the other hand, nothing at all will be seen, either because there are no meteors or because the sky is overcast. Possibly, also, the meteor shower, should there be one. will be on some other night, either before :or after August 4. If however, a meteor shower does eventuate towards the end of this week, the place to look for it will be in the eastern sky in the evening, and, as the night progresses, the northern sky. But any shower worthy of the name will very readily be seen even with a cursory glance. The possibility of this meteor shower is due to a bright comet of the third magnitude which was discovered in a number of countries in the Northern Hemisphere in April this year. This comet was never visible in New Zealand, and is quite distinct from the Pons-Winnecke comet which was observed here recently. The orbit of this Northern Hemisphere comet, which received the formidable: name of Jurlof-Achmanarof-Hassel —a name nearly as long as its tail and compounded of the names of its various discoverers —has now been computed. It is found that the earth will make two clcse approaches to this orbit, one en August 4 and one on January 31 next. The earth, in fact, will be passing through the meteoric debris in the wake of the comet, hence the possibility of a meteoric shower. If the anniversary of the outbreak of the Great War is not marked in the heavens by a shower of meteors, it may be that New Zealand's centeninal celebrations will be honoured by one, ! It should be noted that no one has) definitely said that there will be aj meteor display: only the possibility I oi one, with the why and, the where-j fore, has been pointed out. Two and two put together in the hands of] mathematicians always make four: : the orbits of the earth and of a comet ■ put together by astronomers sometimes make a meteor shower, but not always. Astronomers are. not at all mii clined to be dogmatic about the oci currence of meteor showers. Pro- : phecies have gone wrong in the past, with the result that ridicule has . been heaped on thd heads of those : who made them. All that astronomers- . j will say is that about such and such . a date there will be the possibility of a meteor shower: its exact time and magnitude are just as uncertain as its : occurrence. Gravitational pulls from i other planets have a habit of' upset-! , ting calculations as to orbits, and j , meteor showers are ho respecters of , astronomers' wishes and prognostica- \ tions, COMETS AND METEORS. Until about a hundred years ago meteors were regarded by .astronomers as totally irresponsible visitors from celestial space, coming ip showers or singly at any time they"felt'so disposed. There seemed to be nothing governing their behaviour. But in 1833, on the night of November 12, there was Visible from all over North America a wonderful shower of meteors. So numerous and bright were they that, in the words of one observer, "the stars descended like ■ a snowfall on the earth." It is estimated that at Boston, during a period of 15 minutes, no fewer than 8660 meteor's were visible. For six hours meteors flashed across the sky. their number from midnight to dawn being estimated at 200,000. There is no record, however, of any of them hitting the earth. Now this wonderful display, it was noted, radiated from a fixed point in the constellation Leo, hence they were subsequently known as the Leonid meteors. Astronomers began to investigate the possibility that this shower of meteors was one of a recurring series, and definite evidence was collected which showed ; that the Leonid meteors might be exj pected every 334 years. It was : realiscd. i too, that meteors move in an elliptical! orbit round the sun, the . showers ■ being the 'result cf the earth's orbit intercepting that of the meteors. Then came the discovery of the comet Tempel moving in the same orbit as the Leonid meteors. The return of the Leonid shower was predicted for 1866, and the prediction was fulfilled by fine showers in that and the two succeeding years. A similar prediction was made for 1899, but no meteor shower appeared, and the reputation of astronomers for infallibility was at a low ebb. What had happened was that the orbit of the comet and its attendant meteors had been perturbed by the other planets. Probably the appearance of the Leonids in 1866 is the last that the earth will see of this famous shower. THE LAST BIG DISPLAY. Another famous meteor shower is connected with Biela's comet. This comet split in two, disappeared, and turned into a meteor shower. The biggest meteor shower of the present century was that of October 9, 1933, when, during a period of four hours, thousands of meteors flashed across European skies, much to the alarm of peasants, who sought refuge in churches from the falling skies. This shower was expected by astronomers, but they would have been quite satisfied with a few hundred meteors, whereas the display consisted of at least 150,000. These meteors were moving in the same orbit as the comet Giacaboni, which makes a return every 6_ years or so. If, however, this meteor shower returns this year or next, as it may well do, it is not likely to be seen in New Zealand, the radiant point being too far north. On the other hand, the radiant point of any possible shower connected with the long-named comet mentioned above as having been discovered in April this year is favourably placed for observation in New Zealand. A lesser known, but possibly even greater, shower than the Leonids is the -.yrid shower. This usually gives a mild display each year towards the end of April, but in the past these meteors have provided some very wonderful displays. Chinese records tell of a night in 15 8.C., when "stars fell like rain," and there are ten occasions between 687 B.C. and the present when Lyrid meteors have appeared in sufficient numbers to find a place in historical records. But, as has been noted above, meteor swarms may have their orbits per- ( turbed by other planets, and there is no certainty about their appearance. - Neither are they permanent: in time they must get used up! As regards the possible display this week, one can only hope for the best. If it does eventuate, there will probably be some very varying guesses as to the height of the meteors above the earth. Cal- ; dilations made in previous displays show that meteors vary in height from '.

30 to 60 miles. Therefore, if any meteors seen this week are heard to go "bang" like an exploding rocket, a lively imagination must be presupposed. And there will be no need to wear tin helmets to protect the head from falline debris.