THE LIFE OF A STAR.

Otago Daily Times, Issue 19218, 8 July 1924, Page 4

THE LIFE OF A STAR.

GRAND UNIFORMITY IN NATURE Professor 11. H. Turner reviews certain of tho recent sensational discoveries that have been annoiuioed at tho Royal Astronomical Society. He shows how a very reinarkaJblo uniformity has been introduced into modern views on tho history and de\elopment of the stars. In the article, ■which appoai-s in ihe Morning Post, Professor Turner states: —"Einstein's theory, row • fully established, seems to leave 113 with nothing but relative motion —nothing denoting 'rest' in our universe, nod yet tho calcium clouds to -which Mr livershed first drew attention in lf!19 seem to supply just that standard which Einstein declares impossible. There are, of course, ways of icocnciling tho two ideas, but it is more amusing to leave them, facinsr one another in apparent contradiction. " Scarcely had wo time to acquire c new appetite for Iho sensational when Professor Eddington (of Cambridge) gave us a splendid feast. On March 14 In* put forth 11 revolutionary view of life history o! a star —tha views which ho overturned being those of no one mare conspicuously tlian of himself. It was his own brilliant mathematical work on tho evolution of a star which held tho field, though it was regarded as confirming tho views previously expounded by Professor H. N. Russell (of Princeton, U.S.), which ha had developed from observations of the brightnesses, distances, and spectral type of stars. Knowing tho apparent brightness of a .•■■tar and its distance, wo can calculate it* real or standard brightness—i.e., that which it would have at a selected standard distance. The stars can then be arranged in sequence according to this standard brightness or ' luminosity, an'd it is then found that the spectral type (which represents tho physical slate of the surface) also, ranges itself in the same sequence, which, ns we have come to believe, represents the life history of a, star. "But there is one important proviso—viz., tho same spectral type occurs twice over in tha history, once in the order M. K, F, A, B (to use. the technical letters, the moaning of which, however, need not concern us), and then backwards in the order B, A, F, K, M. Type M denotes both an early ami a late stage in the sequence, just as absence of teeth and hair may characterise either a baby or an old roan. In between these extremes there is' a turning point, and before Professor Kddinglon read his recant paper it was assumed that, the turning point represented the change of the star from the gaseousstate to the liquid (to be followed by the solid in due course). It had previously been a, diffuse, gaseous' giant'; but tho relentless force of gravitation gradually crushed it into a liquid, when its particles could no longer move about freely, and thereafter it became a ' dwarf.* " Professor Fddington had traced these changes raathomaticjilly, but found himself compelled to recognise tho existence of another controlling force besides gravitation, and, indeed, opposed to it—viz., the repulsive force which the radiation of light eerts on all bodies, but especially on small bodies. The particles inside a star are drawn together by gravitation, but radiation tends to keep them apart, though being always les than gravitation it can only delay its action and not overcome it Professor Eddington's work further led him to the conclusion that in a star greater than n certain size radiation would so nearly balance gravity that the merest shake would break the star in two, which explained why we had not come across any stars greater than a certain limit of mass." And. further, that the lower limit (aifio a tact of observation) could be explained by the comparative insignifiance of radiation-repulsion compared with gravity. In between these limits, however, lie assumed that a star could have an arbitrary mass, which would determino its life history ; if its mass were large it would pass through the whole series of changes, from M to B and back from B to M. But if the mass were small, it, might only rise from M to K before becoming liquified and having to turn back towards M. Ihe turning point would depend on the mass of the star, approximately retained as its characteristic throughout its history. "Now, perhaps, it is the simplest way r.f introducing the change with which lie startled us in March to say that he now sun-n-esls the same life, history for every s (a7—the same track for all stars to rim on 1 Thev do not all join it at the same point, owing to the accidents of original mko; -a. massive star will join the track earlv. but on the new vinv it will gradually'become less massive by radiating' itself aw'-iv (for in modern physics radiation is material), and will thus arrive at. the station where a. less massive star is constrained to start, In fact, Professor hudington showed us a diagram of .the line of rails (which in technical terms is a. curve connecting lutniru-itv with mass) with all known stars dinging to them—'know' stars being tbosfor v.hkh the. two necessary elements had Wn <l»lcrmined—and confessed how he hud been bewildered by find hit that all stars, whether 'giants' or 'dwarts were on he rails, which he had thought only suitable f °".\nd"then he gave the revolutionary explanation which had occurred Jo him. We had supposed ciints and dwarfs to he separated bv liquefaction meaning that the particles inside the star had come too close together to move about freely as in a gas. Perhaps, after all. we bad .been wrong? Wb-t if the presumed congestion wore nonexistent? The closeness of the atoms inside a star could bo estimated, and had no doubt been correctly estimated; 'nit what if thev were atoms no longer? The fierce temperature (millions of degrees on our scales) inside a star would doubtless break up the atoms into their constituent electrons and protons, which are so small compared with atoms that thev might have vilenty of room when atoms would be crowded. Sir Oliver Lodge has compared electrons in an atom to flies in a cathedral. The imago liolns us to understand how we might have a cilv in which cathedrals wore so close together as In incur the charge. n f overcrowding, whereas, if wo abolished tl-« bricks and mortar, the few flies inside the cathedrals would be liable to no such suspicion. . "We are still trvmg to digest +ho intellectual feast provided for us at that meeting, but no one vet has complained, as far as T know, that he has disagreed with him • and wo even hope that there may be more dishes of 'imilar excellence to follow." Morning Post.