A SUN IN FLAMES.
STRANGE news has recently reached us from the star-depths. We say news, but in reality the event of which we have just heard must have occurred many years, possibly many hundreds of years ago. A star made its appearance on November 24 last in the constellation of the Swan, not far from the star Rho of that constellation. The new comer was then of the third magnitude. If a star just beyond the limits of ordinary vision had increased in brightness until it shone as a star of the third magnitude, that would show that one among the suns which people space had suddenly blazed out with twenty or thirty times its former lustre. But in reality, something far more terrible than this would seem to have happened. Astronomers have surveyed the heavens far too diligently for a star of even the eighth or ninth magnitude to have escaped their notice where the new star appeared. Arge- lander's charts of the heavens alone include 324,000 stars, or about a hundred times as many as can be seen with the naked eye in the same half of the star-sphere. But the new star is not one among the 324,000. Most probably it was, only a few weeks ago, a star of a magnitude below the twelfth, in which case it was shining last November with seven or eight hundred times its former lustre. It had suddenly, from some unexplained cause, been excited to an intense degree of heat, a change which must have been ac- companied by most disastrous effects if that sun, like ours, was the centre of a scheme of circling worlds. When the catastrophe happened we do not know. We have just said that the new star was shining last November with greatly increased lustre, but we mean simply that it was so shining to our eyes. The light which brought the news to us was probably at least a hundred years on the journey. For we know that from the nearest star light takes more than three years in reaching us, from Sirius some fifteen or twenty years, and probably light takes many hundreds of years in reaching us from most of the twelfth-magnitude stars.
It may be asked, however, how astronomers can be assured either that the new star was not really a new orb, only at the time and for a time—since the star has greatly faded in lustre— assuming the functions of a sun, or that, if really an old sun, it can be called a sun in flames. Of old, the stars that blazed out suddenly in the heavens were regarded as new stars, and as they presently died out, came to be called temporary stars. Such was the star the appearance of which led Hipparchus to construct his famous catalogue, such Tycho Brahe's star in 1572—the re- appearance of which in Cassiopeia may be looked for within the next few years—such Kepler's star in the Serpent-bearer. All these blazed out until they exceeded in brightness every fixed star in the heavens, and even Jupiter at his brightest, being surpassed by Venus alone. They were all three visible, in fact, in full day- light. They soon lost this splendour, however, and none of them remained visible more than sixteen months. But when a bright star appeared in the Northern Crown in May, 1866, which in old times would have been regarded as a new star, astronomers found the benefit of their careful survey of the heavens. The star was only new as a bright star, it had been observed twice in Argelander's survey of the heavens as a ninth-magnitude star. And again, after it had faded from ordinary vision, astronomers continued to observe it with their telescopes. It did not dis- appear from their view, but remains visible, with a telescope of rather small power, to this day. This is the star T—not Tau, as Roscoe mistakenly calls it—of the Northern Crown. It was the same body which first showed astronomers what has hap- pened when a new star makes it appearance. Examined with the spectroscope, it gave the rainbow-tinted streak, crossed by dark lines, which implies that a star is a sun like our own,—a glowing mass of solid or liquid matter, shining through relatively cool, though absolutely very hot, vapours. But it gave, besides, a spectrum showing that such a sun had suddenly been en- wrapped in flames of glowing gas. For on the rainbow-tinted streak, as on a dark background, there were seen the lines of hydrogen, not dark as usual, but intensely bright. The well- known interpretation of this appearance was that the hydrogen surrounding that star was not, as usual, cooler than the glowing body of the star, but hotter, and very much hotter.
The star which has just appeared has given similar, but more decisive, evidence. Besides the bright lines of hydrogen, the
spectrum of the new star shows the double orange-yellow bright line of sodium, or, perhaps (for the point cannot be determined), the line of that unknown element which produces the most marked orange-yellow line in the spectrum of the sun's coloured prominences, the triple bright line of magnesium, and two other bright lines, one of which seems to be identical with a line given by the solar corona during total eclipse. It is noteworthy, and to say the truth, somewhat portentous, that the elements to whose intense heat the new star owes its increase of brightness are pre- cisely those whose lines form the most characteristic features of matter surrounding our Sun. M. Cornu, who made the observa- tion, declines to form any opinion on the meaning of this fact, assigning as his "exquisite reason" that, "whatever attractions hypotheses may have, it is necessary not to forget that they are unscientific, and that far from serving science, they greatly tend to trammel her" (which is about as just as though one should say that whatever attractions the use of raw material in manufacture may possess, we must not forget that manufactures are not the raw material, and that far from tending to encourage the producer -of the raw material, they greatly tend to trammel him). Fortu- nately, Newton, Galileo, and some others whose names are not wholly unknown to science, have been willing to think as well as to observe, and their " unscientific " example has been followed in our own time. Accordingly, after Mr. Huggins had determined the spectrum of T Coronaz, he reasoned about its meaning, and so effectually as to suggest one of the most fertile methods of observation yet invented,—the spectroscopic method of seeing the Sun's coloured flames. Certainly M. Cornu, who has ac- quired well-deserved repute by observations which never would have existed had not reasoning been applied to observed facts, should not object to reasoning as unscientific. It is, indeed, impos- sible for any thoughtful student of science to avoid reflection upon the significance of what has been observed in the case of the new star in Cygnus. Here we find the same elements which exist in our Sun, but ordinarily in such a condition that they partially absorb Ids lustre, have in the new star been excited to so intense a degree of heat, that their light is very much stronger than that of the globe they envelope. The fact is rendered still more significant by the circumstance that in the case of our own Sun those same elements occasionally glow with a heat more intense than that of the Sun's own surface, though—fortunately, perhaps, for us— the increase of heat is only local, and very limited indeed in range. Tacchini noticed that during ths great heats of a recent summer the magnesium in a portion of the solar sierra was heated in this abnormal way, and though there may have been no real associa- tion between the heated magnesium and the hot weather experi- enced over nearly the whole of our northern hemisphere, yet, on the other hand, the association may have been very close indeed. The Astronomer-Royal for England has lately noticed, as the Astronomer-Royal for Scotland had observed earlier, that our earth receives in some years more heat from without than in others. We now see that suns which have unmistakably blazed out with many times their usual degree of lustre have had the constituents of their exterior atmosphere superheated, in the same way as the corresponding elements in the Sun's atmosphere are occasionally ,(though but locally) superheated. The question naturally arises whether the cause which produces the effects observed in our own Sun is not, in all probability, of the same nature as that which produces great solar outbursts ; and if so, whether it is altogether certain that this cause may not one day operate much more ex- tensively and effectively on our own Sun than it has yet done, and produce such an outburst as seems foreshadowed in the description of the day "when the heavens shall pass away with a -great noise, and the elements shall melt with fervent heat ; the earth also, and the works that are therein, being burned up." Fortunately, great outbursts occur so seldom among the millions of stars within telescopic range, as to suggest that the chance of any given sun,—our own, for example,—suffering in this way is 'but small. Moreover, Sir J. Herschel (who was not afraid of trammelling science by that unscientific process called thinking), has noted that the danger seems limited to those suns which belong to a particular region of the Milky Way,—a region to which our .own Sun does not belong.
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