IN STARRY SKIES

Evening Post, Volume CXV, Issue 105, 6 May 1933, Page 23

IN STARRY SKIES

(By "Omega Centauri.")

SPECTROSCOPE CONFIRMS BICKERTON'S PREDICTIONS

Professor A. W. Bickorton was [ primarily an engineer, a chemist and a physicist, rather than an astronomer. But his attention was drawn irresistibly to cosmological problems by tlio appearance, on November 24, 1876, of a Nova of the third magnitude, near the star Rho in the constellation Cygnus the Swan. This outburst was a verymild one in comparison with that of Tycho'g star of 1q72, or that of Kepler jn 1604, but Bickerton was practically alone in realising th.c stupendous character of the phenomenon.' He was amazed at the utter inadequacy of the solutions offered to account for it, such as a volcanic eruption on a dead sun, or the lighting up of the atmosphere of such a body by the passago through tit *f a train of meteorites. At the present day there is a' tendency to ascribe all occurrences that cannot be explained to the action of sub-atomic forces behaving in some unknown way. But Bickertoiij in papers read before the Philosophical Institute of Canterbury on July 4, and August 1, IS7B, hot only stressed the astounding nature of the occurrence but showed that the whole sequence of phenomena could be explained without invoking the action of a singlo unknown force. It is not only the magnitude of the outburst that has to be explained, but its suddenness and its transitory character. In a few hours a star rises from invisibility to shine with an intensity which sometithe's'exceeds that of our sun tens of thousands of times. Then within a few days, weeks or months, it sinks *again into insignificance. Such an outburst Is universally recognised today to be an explosion of a violence utterly transcending' any other known in the whole realm of nature. Yet even now there are advocates of such theories as that which tries to explain the scquemce of events by the passage of a star through a nebula. With the density usually associated with gaseous or dark nebulae, the encounter would have to proceed for untold millions of years, instead of a few hours, to liberate the observed radiant energy; and if the star were heated to a temperature that makes it shine with thousands of times the intensity of the sun, it would take not only millions, but millions of millions of years to cool. Bickerton saw at once that no force then known except gravitation was competent to liberate the required energy. , A mass falling on to the sun sets free ten thousand times the energy that is developed by the combustion of the sanie mass of oxygen and hydrogen mixed in the requisite proportions. Two stars colliding would clearly provide all the energy displayed. But a complete encounter could never account for the rapid fading which is such a characteristic feature of every Nova. To account for the peculiarities of a typical Nova, the collision must be a partial one. When stars come into grazing collision with relative speeds of hundreds of miles per second, a third body is inevitably formed. The shearing foreo required to cut a part from each has its upper limit in the latent heat of fusion. The work of cutting off the parts that come in one another's way is thus not greater that a millionth part of the available kinetic energy. The formation of a third body in the case of a celestial collision, turns out to be the foundation stone of a new cosmic philosophy. It not only explains new stars, double stars, variable stars, comets, gaseous nebulae, planetary nebulae and gigantic spirals, but it indicates the possibility of processes which conteraet the dissipation of energy, -ahduso the conception of an immortal cosmos^ Bickerton. saw that a direct impact of two equal gaseous suns would transform into heat just sufficient kinetic energy, that is excepting the comparatively small part due to original proper motions, to expand the mass to double the" original diameter of one, at the' original temperature. The increase of light would'thus be less than I one magnitude, "but it Would be millions of millions of years before this increase completely disappeared. Now in the first twenty years of the present century five bright Novae appeared whose distances have been approximately determined. These were the New Stars in. Perseus, Lacerta, Gemini, Aguila, and Cygnns. Their distances' range from 125 to 1630 light" years, and the average increase in brightness amounted to 11.7 magnitudes, that is their output of radiation increased nearly 45,000

times, or 24,000 times as much as we could expect in the case of a direct collision. Now, can the third body perform such a miracle? Apparently that is exactly what it can do, and one of the most conclusive proofs of the truth of the partial impact theory is that Bickerton was able to predict numerous pccularities 'in the spectra of Novae practically all of which have been observed during the last half century. In the case of a grazing collision the two wounded stars pass on. They are for a time a pair of variables, and they may bo wedded into a binary system. But with these developments we arc not concerned at present. The portions torn from the stars coalesce into a, strangely constituted whirling mass. It is as highly heated as if the bodies had collided directly. But it has only a fraction of the mass to restrain the movements of its atoms. [Its densest parts, coming from deepest down in the two stars, are at opposite ends of a diameter and are moving in opposite directions. The whole mass is therefore spinning violently. The lightest elements are imprisoned at first in the centre of the whirling mass. The whole body is initially so violently compressed that its atoms are quite unable to execute their characteristic dances. The initial spectrum is therefore a continuous one. But the mass being relatively small, and the temperature so astoundingly high, expansion takes place at an unprecedented rate. An onward speed of hundreds of miles per second has been transformed suddenly into atomic agitation. The pressure is terrific. The atoms near the surface arc urged outwards by incessant blows from behind. Soon there is an atmosphere of mixed elements, which produces, by its absorption, thin dark lines in the spectrum. But before long the principle that Bickerton named "Selective Molecular Escape" makes its influence apparent. Directly after the shock atoms of all kinds have approximately the same speed. Atoms of lead and of hydrogen for instance have each had an onward motion- of 200' or 300 miles per second changed suddenly into a vibratory one. An atom of lead haviug 207 times the mass, if moving at the same speed, has 207 times the energy of an atom of hydrogen. When they meet tho hydrogen atom bounces from the lead one with increased velocity like a cricket ball from the bat of a mighty hitter. The temperature tends to become equalised, and thus there is an approach to equipartition of eneVgy, the nydrogen atom having a share equal to that of one of lead. The hydrogen atom must then be moving more than 14 tiroes as fast as the atom of lead. Thus the lighter atoms will gradually find their way outwards, and the whirling mass will be surrounded by an atmosphere of hydrogen, helium and other gases, rushing outwards at speeds over which the gravitational attraction of the third body has little appreciable power. In actual cases that have been observed, the escaping hydrogen has been found to move outwards in all directions at speeds of about 1500 miles a, second. The sphere of glowing hydrogen so produced soon gives bright bands in the spectrum, but the brilliant nucleus is shining through the gas that js coming directly towards us, so every bright band will have a dark fringe on its more refrangible side. Wo must leave till next article the further strange changes in the character of the spectrums.