SIZE OF THE UNIVERSE

Wanganui Chronicle, Volume LXXXI, Issue 19032, 7 June 1924, Page 11

SIZE OF THE UNIVERSE

ASTRONOMERS REVISE THEIR ESTIMATE.

A nebula so small that it is invisible to the naked eye and so far away that it takes a million years for its rays to reach the earth, has caused astronomers to revise their estimates of the size of the universe, according to the Abbe Moreux, the French scientist, who is a frequent contributor to the Petit Journal. Writing o n the subject the learned Abbe calls attention to the fact that new estimates of the extent of the universe must be based upon the foundation laid down by an American Horrow Shapley, of Mount Wilson Observatory, who in 1918 discovered that rays from the most distant star cluster of the Milky Way take 200,000 years to reach the earth. Since then, says Moreux, Sharpley has I gone further afield. “I do not believe ’’ he writes, “that there exists in the whole domain of astronomy, vast as it is, a more absorbing study than that of -the nebula, the name which the astronomers have given to those little milky spots or patches with which the sky is scattered. “Formerly, before the invention of the telescope, the ancients used to include in their records —restricted it is true —all objects which appeared nebulous to the naked eye, but since glasses have, provided the means whereby the savants have been able to scrutinise the heavens a distinction has had to be made. “To-day confusion is barely possible; clusters of stars and nebulae are of quite, a different nature. DAILY INVESTIGATIONS MADE “For certain objects, all instruments employed have been useless tQ determine them. The ? jjebnlao proper are but huge masses of gas in process of condensation, and each day by means of photography our investigations seem to multiply them immeasurably. “At the time of Willainv Herschel. t|’e known number of nebulae was little more than 2000, whereas the telescopes of the nineteenth century could distinguish as maity aS 120,000. It is not too much to say that it is possible by means of the famous mirror which is used at. Mount Wilson, in America, to bring this number up to a million, either by direct vision or by photographic procedure. “Such a prodigality is surely enough to convince even the doubters that the field of astronomy is’vpractifcally unlimited, and in spite of the discoveries of which mankind is proud there still remains a vast horizon to be explored, and which is much greater than our timid investigations had caused us to suppose “We shall leave aside the question, interesting though it be, of origin, constitution and evolution of the nebulae. There is too much mystery still, and even our greatest scientists must hesitate before such formidable

enigmas. “Where do we come from? From a nebula, originally round, said Laplace. But why is it that those which we see, the least advanced in their evolution, nevei take this form? The greater part of them are of a spiral shape, with two distinct branches. Jt is also quite possible that the nebula of which this world is the issue was at the beginning, that is to say some milliards of years ago, of a like constitution. This question of spiral nebulae is one which is greatly interesting to savants. “In passing over these speculations, fqr which our minds are not yet ripe, we come to a subject which is more accessible. Where are the nebulae? THE MILKY WAY. “Until now, the greater part of astronomers, those who devote themselves to science, not romance, have admitted that all objects affected by our instruments were enclosed within a space clearly determined, and which is none other than the Milky

Way. So this immense formation, which represents in our eyes our universe, is said to contain not onls about two million stars, but also all the stellar groups and all the nebulae. In fact, we have been convinced for some time that certain nebulae such as Orion, or Andromede, form an integral part of the Milky Way. Thii is because we have been able to mea sure the distances. For the lessei nebulae the distances were unknown and so the doubt has been permissible. “Some astronomers have supposed, as did Herschel at one time, that the apparent smallness of the nebuUl and their feeble light were on ac count of the immense distance of these mysterious objects which one likens io a different universe than ours, tnd comparable to our Milky Way. These conclusions appeared all the more legitimate when about ten years ago, according to the specialists iu stellar matters, one could only attribute to <*ur Milky Way some thousands of ‘light years in diameter. “Newcomb in particular said that a luminous ray, which moved at a speed of 30-0 000 kilometres a second, would take a maximum of 15,000 to 16.000 years to cross our universe. So, generally speaking, the star clusters and nebulae appeared much further away. “But. by applying relatively new methods for determining distance, Horrow Shapley. of Mount Wilson, definitely established in 1918 that our Milky Way showed much greater dimensions; in fact no fewer than 300.000 light years, and the farthest

away star-cluster which was examined took 200,000 years to reach us. It also appeared that the elements of our Milky Way were accessible to our instruments. There were still a few doubts, but these were left to the future to clear away. SHAPLEY S POSITION. “Although a stellar speed of 5(l0 kilometres a second was a rarity, it was discovered that for many of the lesser spiral nebulae the speed was something like 1200 kilometres a second. This seemed to us as foreign to our universe, represented by the Milky Way, but it. was by no means the opinion of Shapley ( This is t rather a piquant remark to make, but ! it is this same astronomer who now brilliantly demonstrates the _ inanity of his first affirmation. “There exists an extremely smal’ nebula in the heavens. It is invisible to the naked eye, and has been registered in the catalogue of Dreyer under the number of 6822. This object of sixteenth greatness looks like a reduction of those large white patchef known under the name of Magellan multitudes, and which shine on tha edge of the Austral Milky Way. Through the telescope it looks like a lot of little clusters mixed with many lesser nebulae, and as the stars which arc visible in this limited field are barely of the eighteenth greatness it was inferred that the nest of nebulae

was an immense distance aw r ay, but whether the distance was greater than that of the cluster at 223,000 light years it is not possible to say. So Shapiev resolved to take up this interesting problem, and what do you think he discovered? “The celestial object which answers to the number 6822 in the new cats logue of nebulae is to be found at a million of light years; that is to say, the luminous ray which reaches us at ’this moment when we are contemplating this nebula has been travelling for a million years.

“It is therefore not a part of oui Milky Way, which w r e call our universe. It is apart from it, and,, like it no doubt, travels across the vast abysses of the heavens. Where is it going to? Where are we going? Mystery of space! How small we feel in the face of such great problems.’*