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STRANGE NEWS FROM AUSTRALIAN SKIES.

[From the Spectator, 11th December.] More than a year ago a discovery was announced by an astronomer in the Southern Hemisphere, which seemed "so strange and so perplexing, that Sir John Herschel commenting pn it, remarked, " that no phenome non in astronomy had yet turned up presenting anything like the same interest, or calculated to raise so many and such momentous points for inquiry and speculation." One of those mysterious nebulous masses, which astronomers had been in the habit of regarding as galaxies, resembling in extent and magnificence the sidereal scheme to which the sun belongs, seemed to be undergoing the most astounding series of changes. During these winter nights, when Orion shines with full glory, the famous nebula which clings around hjs pendant sword presents to our northern observers an object similar to the nebula in question. Everyone has heard of the strange interest which attaches to this Orion nebula—of the mysterious, far-reaching arms which extend from it—the dark central yacanc) —and the brilliant array of stars which the six-feet mirror of Lord Rosse has brought into view in the very heart of the nebula. But in the Southern skies there is an object of the same class even more glorious and mysterious. In phe richest part oi the southern heavens —a part so rich indeed that, according to the argument of a well known astronomer, the splendor of the constellations comprised in it illumines the heavens as a new moon would—there lies the great nebula among astronomers as " the nebula in Argo." The Orion nebula pan only be seen on the darkest nights, but the great A rgo nebula shines as a third-magnitude star, and is scarcely obliterated even by the effulgence of the full moon. It is, in fact, the most splendid nebula in the whole heayens. Yet this glorious object, whose contemplation has led our most thoughtful astronomers to form new ideas of the grandeur pf the universe—whose dimensions, seemed immeasurable by any unip of length men could devise—phe whole of this magnificent nebula js drifting about like a cloud before a. shifting wind.

For the news which seemed so Surprising to Sir John Herschel has iyist been confirmed by the reyelai ions of a new telescope pf enormous p.ower. The news hacl pome, first of j|ll, from a ?>mall telescope—only five JBgJ&p \n aperture; and it seemed

quite possible that the weakness of this instrument (compared with the 19-inch reflector used by Sir John Herschel during his survey of the southern heavens) might have led to an erroneous impression of change. But now the four-feet mirror is at work among the Southern star l . Surpassed only by the Rosse reflector and matched only by the fine reflector with which Lassell is surveying the heavens at Malta, the great Melbo uurne reflector is about to place our knowledge of the Southern heavens nearly on the same footing as that we possess respecting the Northern stars. And if the work to be done by this great reflector in after years is shadowed forth by its great exploit, we may well look eager! v forward for the discoveries it may effect. j Sir John Herschel had said, a year and more ago, that the inquiries suggested by the news then lately leceived about the Argo nebula "must be settled." We cannot do better than use the ipsissima verba of the great astronomer : —" The question," he said, " is not one of minute variation? of subordinate features, which may or may not be attributable to differences of optical power in the instruments used by different observers, as in the case of the Orion nebula, but of a total change of form and character—a complete subversion of all the greater and most striking features—accompanied with an amount of relative movement be tween the star and the nebula, and of the brighter portions of the latter inter se t which reminds us more of the capricious changes of form and place in a cloud drifted by the wind, than any tiling heretofore witnessed in the sidereal heavens."

Urged on, doubtless, by the importance thus attached to the question by the greatest astronomer of the day, Mr Le Sueur turned the new]y mounted reflector to the great nebula. The result is now before us. There seems now no longer the least room to doubt that the nebula has changed in a marvellous manner since Sir John Herschel, a third of a century ago, mapped its most striking features. The stars which are strewa over the nebula, and which had been spoken of by Sir John Herschel as probably much nearer to us, have remained unchanged in position, and, with one exception, have not changed much in relative brilliancy. So that Mr Le Sueur has been led to form the opinion that the nebula is much nearer to us than the stars —a view clearly' tending to diminish our ideas of ihe real dimensions of the nebula, and so rendering the observed changes somewhat less astounding than they otherwise would be. Forbearing to speculate—as, indeed, we have no means of forming an opinion—about the physical causes to which these| marvellous changes may be due, let us consider a little the conclusion! to which Mr Le Sueur has been drawn. Because the stars seen with the nebula have remained unchanged v»hile the nebula itself has shifted about so strangely, the opinion is suggested, says Mr Le Sueur, that the nebula' and the star are in no way associated. And certainly one would expect to find the changes of the nebula accompanied by very remarkable changes, in the star-group, if there weie any bond of association between one and the other. Changes more remarkable perhaps than have been noticed in any other part of the sidereal heavens might be looked for.

What, however, if this were actually the case, despite the fixity observed among the stars examined by Le Sueur ? We have spoken of one exception to the constancy of these stars in brightness, what if that exception should be more than sufficient of it* elf to compensate for the fixity of the other stars? The star that has changed is the famous Eta Argus, the most wonderful star in the whole heavens, and only surpassed in interest by one object—the nebula in the inidst of which it is situated. ~ j

Jt vyas marked in Halley'?- catalogue as a fourth-magnitude star; in Lapaille's, as of the second magnitude : in 1843, it surpassed every star in the heavens in brilliancy qx-.,

cept the Dog Star; at present it cannot he seen with the naked eye. When Sir John Herschel wa* at the Gape, the star was nearly at its brightest, and then the nebula could not be seen even on the darkest night. Now, when the star is invisible, the nebula shines with a lustre which renders it visible before the thirdmagnitude stars come out upon the evening skies; and probably its brilliancy, if not diffused, would make it appear as soon each evening as though it were a first magnitude star.

Is not the idea suggested that these, interchanges of light; are not merely apparent and fortuitous? that in in some way Eta Argus has given up its brilliancy to the surrounding nebula to resume it again when the cycle of its changes is approaching completion ? We have every reason to believe that the star's variations are really periodical, though the cycle of changes is exceedingly complex; indeed, astronomeis have already indicated the clo<e of the present century as the epoch when the star will have resumed her full splendor. If this view is correct, the nebula must be looked upon as neither beyond the star-group, as Sir John Herschel, surmised nor nearer to us. than that star group, as Le Sueur thinks, but as mixed up with it. This view is not a new one. In March, 1868, long before the news had been received that the nebula is changing in figure, the author of this paper, in an article which appeared in the Scident for that month, pointed out that that there is an obvious connection between the nebula as depicted by Sir J. Herschel and the fixed stars seen in the same field. "There is not,'' he remarked, "a single remarkable condensation or projection in the nebula which is not marked by bright or clustering stars —by stars which appear clearly to be leading stars; and there arc not ten (out of some hundreds entered) whose influence on the nebula is not discernible." If, now that the nebula has assumed a new figure, the same sort of connection should be observable, no doubt can any longer remain that this nebula (and therefore presumably every other nebula of the same type) is associated with the stars which are seen in the same field or view with it.

Permanent link to this item
Hononga pūmau ki tēnei tūemi

https://paperspast.natlib.govt.nz/newspapers/HBT18700425.2.10

Bibliographic details
Ngā taipitopito pukapuka

Hawke's Bay Times, Volume 15, Issue 781, 25 April 1870, Page 4

Word count
Tapeke kupu
1,478

STRANGE NEWS FROM AUSTRALIAN SKIES. Hawke's Bay Times, Volume 15, Issue 781, 25 April 1870, Page 4

STRANGE NEWS FROM AUSTRALIAN SKIES. Hawke's Bay Times, Volume 15, Issue 781, 25 April 1870, Page 4

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