SOME LESS SPECTACULAR NOVAE

Evening Post, Volume CXVI, Issue 49, 26 August 1933, Page 22

SOME LESS SPECTACULAR NOVAE

(By "Omega Centaur^.) j After the brilliant Novae of 1572 and 1604, associated with ,the names of Tycho Brahe and Kepler/,' few observations of anything resembling ' them were made for tiro an/I a half centuries. In the few cases 'j,'f change recorded amongst the stars/during that long interval, it is hard £0 say whether the object seen was a.ii-ue nova or a variable star. Two p/ieh bodies had been noticed between tho appearance of Tycho's sta,r and that of Kepler; namely, Mira '<3eti, discovered in 1584, and a third ijiagnitude star which appeared in Cygryus in 1600, which had a second maxin/um between 1657 to 1659. It is kr/bwn still as P. Cygni, and, since its Spectrum bears a resemblance to that of a nova, is classed also as NVI6OO. Another star of the third magnitude . appeared near Beta Cygni in 1669. It disappeared, but was seen again in 1671 of the fourth magnitude, and' after another disappearance it shone out again, but aiore faintly, a year later. Since then it hrn not been j observed. A possible nova in Orion was observed in 1667 and again seventy years later. A sixth magnitude star was seen •on three consecutive nights in 1783 in the constellation Sagitta. The wonderful variable Eta Carinae has often been classed as a nova. It was observed by Halley in 1677 as a fourth magnitude star. In 1685, 1751, and 1826 it reached the second magnitude. In 1827 it rose to the first, but fell to the second again during the next year and continued so f(v several years. In 1843 it rose to the magnitude denoted by minus one, which means that it was then nearly as bright as Jupiter. After that it slowly declined, and is now two magnitudes fainter than any star seen with the naked eye. At'last in 1848 a typical nova appeared. It was discovered'by Hind,

the .great, authority on comets, in the constellation , Ophiuchus. It was : then below the fourth magnitude and rapidly faded away. Its colour was- described'as a. very intense reddish-yel-low. In 1866 it wa: about the twelfth magnitude, and by 1575 it had f alien ' to the thirteenth. < On-May'2l, 1860, a new star was discovered by Auwers in the globular cluster MBO, which lies between Alpha and Beta Scorpii. It was only of the seventh magnitude, but was blight enough practically to hide the cluster, which' seemed to "have been replaced by the star. By June 10 the star had almost disappeared and ' the cluster showed: once more in all its beauty. This was the first definite cas ■of a nova -appearing in a star cluster, and it seems, to have suggested the possibility , of: such outbursts being due to collision amongst,the stars. A more important nova, which was called, "The Blaze Star," appeared in Corona .Borealis. on 'May 12, 1866. 'It is specially interesting in the history of astronomy as it was the first nova to be examined through tho spectroscope. Huggins found' its spectrum to -consist of bright'hydrogen lines superimposed on a continuous spectrum crossed by many , dark lines. When first seen this star was shining with the second magnitude, where it was certain that nothing as bright as the fifth magni:. tude had been visible 24 hours earlier. By next evening it. had sunk to the third magnitude, three. nigh.sS later to the fourth, and by the end of :the month to the ninth, and it is now belov- the tenth. . Although' this star never attained any striking brightness it started a new era in cosmogony. The speetroscopic observation- of Huggins in England, and AVolr and Eayet in France orovided. sound data [on

,'niiich it was possible to found some hypotheses as to the origin of the outburst. Clear!) a great part of the light came from glowing hydrogen. But how was the l.ydrogen ■ evolved and how was it rais'-u to incandescence! Huggins suggested that owing to some internal convulsion enormous quantities of hydrogen and other gases were ejected from tho star, and then set on fire. There werOj however,, no lUies detected which indicated the presence of oxygon. The sudden fading of the star vas attributed to the failure of the supply of hydrogen, and tho cooling of the photosphere which was supposed to have been heated only on the surface. Meyer and .Klein suggested that tho outburst may have been due to the precipitation of some great mass, such as a planet, on to the surface of the star. Proctor pointed out later that if i planet approached its parent star it would do so gradually, and when at last it touched the star it would only graze its surface on its .nearest approach. There would thus be a succession of recurring impacts. Another suggestion by Meyer and Klein was that the star may have collided with a nebula. Proctor suggested that an enormous flight of meteoric masses, travelling around the star, may have come into contact with its atmosphere and been raised to incandescence as tho.ie are which strike our air. ; 'All these suggestions are quite unable to account for the outburst now that it is known To be on a far more stupendous scale than anyone then imagined. The question thus arises: Are such speculations of use, or are they. a hindrance to science ? An interesting discussion of this .question was given by E. A. I^rocto in an essay on "The ■ New Star which faded into star-mist," published in his "Pleasant Ways in Science" in 1895. His answer depends on the distinction between an hypothesis and a theory. In one dictionary I find that hyopthesis is "a supposition, something not proved but assumed for 'he purpose. of argument, a theory imagined or assumed to account for which is not understood." A theory, on the other hand, is "a philosophical explanation of phenomena." M. Cornu, who made some of■ the earliest speetroscopic observations of the next nova discovered, said: "Grand and

seductive though-'the task ; may be ;of endeavouring to-draw 'from' the observed facts inductions respecting the physical' state of this'new star, respecting .its' temperature, and the chemical reactions of, which it' may :be" the scene, I shall, abstain' from all commentary and all hypothesis on this subject. . . . However attractive hypotheses may be, we,must not forget that they are outside the bounds, of science, and ( that, far . from serving science, ■' they seriously endanger,its progress."' Proctor rejoins that this is utterly inconsistent with' all experience. He adds that many .when they hear the' word hypothesis think immediately 'of ■ Newton's famous dictum: "Hypothesis non fingo" but. forget. the qualifying words. "I frame no hypothesis," he says, "for whatever is not deduced -from' phenomena is to be.called an hypothesis." It would be, absurd to suppose that Newton who advanced, advqeated, and eventually established; ther'.-noblest scientific theory the world has known, would- ever have expressed aii-objec-tion to theorising,. Theories-properly used draw. the attention of " the ; observer to thirigf which'otherwise would be overlooked! Of course science may be' arrested if an' observer' is so - strongly influenced by his theory that-he' sees things which' do not exist, but in: that case the observer is niore to.blame/than ■the author'^ofthp. theory.- Then, again isolated facts are uninteresting and difficult to remember. When they are connected and ■ explains, by a.true theory, or even temporarily .lilting* together by a plausible working 'hypothesis, they, fbrni-a firm., takiag-off ground when on the quest for-further facts...: , Even the total; inadequacy, of the hyoptheses mentioned aboye,:. helps, us to realise the astounding nature of tho phenomenon.' ; ■ -