Temporary Stars

( Originally Published Early 1900's )

HISTORIANS of various dates and nationalities tell us that from time to time stars have blazed forth in the heavens in places where no stars had ever been seen before, and that after an existence of, it may be, a few weeks or months, such stars have faded away and been no more seen. It was at one time considered that the authors of these statements had been drawing upon their imagination for their facts, but the bulk of what has been handed down to us are well founded. About 12 stars in all are recognised by astronomers under the designation of " temporary stars." They severally appeared as follows : 134 B. C., 329 A. D., 1572, 1600, 1604, 1670, 1848 (Nova Ophiuchi), 1860 (T Scorpii), 1866 (T Corona), 1876 (Nova Cygni), 1885 (Nova Andromedae), and 1892 (Nova Aurigae). The chief difficulty in regard to all the more ancient cases has been to determine how far the celestial objects thus recorded to have burst forth were in any true sense stars, or whether they were comets or mere meteors. The records which we have are of very diverse origin, and some of them z000 years old, handed down to us from times when the scientific precision and verbal accuracy of modern writing and speech were unknown. The fact that the ancient Greeks were a dreamy people, the Romans callous to science altogether, and the Chinese " flowery " as nowadays, renders it extremely difficult for us to sift the wheat from the chaff, and to préciser, as the French say, any given statement. For instance, what is one to make out of the following Chinese account of something seen in A. D. 173 : " On Dec. 10th a star appeared between a and ß Centauri, and remained visible for 7 or 8 months , it was like a large bamboo mat (!), and displayed 5 different colours." Were it not for the fact that on several occasions during the present century new stars have burst forth, have shone for a while, and have then either disappeared absolutely or dwindled almost to invisibility, we should often have to be sceptical as to the tales told us by many ancient chroniclers.

Our sources of information are twofold European and Chinese. The former are generally very vague as to dates and places ; the latter much more " understandable," though both dates and places are often expressed in a very peculiar fashion. The Chinese observations have the great merit that they are continuous through many centuries, and are expressed in language of very uniform style ; so that once get an insight into the style, and a European astronomer may feel sure that he can interpret with tolerable accuracy the entire series, and this is what has been done. The first workers in this field were certain French Jesuit missionaries, named Couplet, Gaubil, and De Mailla, who lived for a while at Pekin some 150 years ago. They made and brought to France copies of various Chinese annals, which somehow or other they got hold of at Pekin. De Mailla's manuscripts were published at Paris about too years ago, but those of Couplet and Gaubil still remain, I believe, unpublished. A very industrious Frenchman named Pingré worked up all these materials in a book on comets which he published in 1784, whilst another Frenchman named Biot in 1846 gave to the world a further series of observations. By far the most complete and accurate, however, of all the existing versions of the Chinese astronomical records is the late John Williams's "Observations of Comets from B. C. 611 to A. D. 1640," which appeared in 1871.

All this is a digression from the subject which I wanted to start with, but it is a digression which seemed necessary under the circumstances of the case.

The earliest " new " star appears to have been one observed by the Greek astronomer Hipparchus, and a tradition, fathered by Pliny, has always suggested that it was the appearance of this star which prompted Hipparchus to compile his, the first catalogue of stars. This tradition was long regarded as a myth, but as a new star in Scorpio is recorded by the Chinese to have been seen in 134 B. C., a few years before the date commonly assigned to Hipparchus's Catalogue, there seems now no sufficient reason for rejecting the tradition above referred to. Passing over new stars asserted to have appeared in 945 A. D. and 1264 A. D., the authenticity of which is gravely doubtful (the accounts probably referring to the great comets of those years), we come to the year 1572. In that year there was a celebrated new star with which Tycho Brahe's name is often linked, because he left behind him a particularly full account of it. It was visible for 17 months from November, 1572, to March, 1574. Brighter than Sirius, it rivalled Venus. It changed colour from white to yellow and red and then back again to white, and remained stationary all the while that it was visible. D'Arrest pointed out in 1864 that within 1' of arc of the place assigned by Argelander to Tycho's star there exists a small star, which Hind and Plummer found in 1873 to be certainly variable in its light. The position for 1890 of Tycho's star is R. A., oh. 18m. 40S.; Decl. + 63° 32'.3. Amateurs possessed of telescopes, say of 3 inches aperture, might usefully em-ploy their time in finding and watching this supposed Tycho star. It follows a certain 9th mag. star at a distance of 21.6s., and is 10' 4" to the S. This 9th mag. star may itself be identified by reason of the fact that it follows a star known as Flamsteed's 10 Cassiopeiae (mag. 6) at a distance of 17m. 12s., and is 6.4' to the N. of it.

In 1604 and in 1670 temporary stars of considerable brilliancy became visible. The star of 1604 appeared in Ophiuchus, and grew to be nearly as bright as Venus, lasting 12 months or longer. The star of 1670, often called " Anthelm's star," appeared in Cygnus, and reached the brightness of a star of the 3rd mag. It lasted altogether about 2 years, but faded away and then brightened up again more than once before its final disappearance.

In April, 1848, a new star of the 5th mag. was seen in Ophiuchus by Hind. It eventually rose to the 4th mag., and then faded away and became very small, but has never entirely disappeared. This star is now ranked as a recognised variable, but it seems not to have received much notice of late years.

In 1866 a very remarkable transformation took place in the case of a star which had been previously recorded in 1855 by Argelander as being of the 9th or loth mag. Birmingham at Tuam, on May 12, 1866, found the star shining as of the second mag. Combining the testimony of Birmingham with that of Schmidt of Athens, it would seem that this star brightened up from the 4th to the 2nd mag. in about 3 hours on the evening of May 12. It soon began to lose light, and after diminishing to below mag. 9 it rose to 7 in September, and remained at that for the rest of the year. This star also is now treated as a recognised variable, though we have gained very little additional knowledge respecting it.

In November, 1876, after several days of pronounced bad weather, Schmidt at Athens observed on the 24th a new star of the 3rd mag., yellow in colour. By the beginning of December it had sunk to the 5th mag., and by the end of December to the 7th mag., and now it seems to have disappeared altogether.

In August, 1885, a new star burst out in, or in front of, the Great Nebula in Andromeda. Though it only reached the 6th mag., yet, owing to the large number of telescopes and spectroscopes brought to bear on it, this nova has a considerable and very interesting history attached to it.

One moral to be drawn from this is that amateur observers need not fancy that there is no work for them to do in Astronomy. Respecting this star, I will here state historically what seems to have happened. The Great Nebula in Andromeda is one of the largest and most important of the known nebulae, as we shall see when we come to speak of that class of celestial objects. It ordinarily offers the appearance of an extensive and dense oval mass of luminous haze. It so presented itself to various observers during the first half of August, 1885. Priority in noticing it to be otherwise that is, as having a star in or on it seems to rest either with the late Mr. Isaac Ward, of Belfast, or with a Hungarian lady, the Baroness de Podmaniczky, who on August 22 had staying with her at her husband's house professional astronomer, Dr. De Kovesligethy. There was a telescope of 31 inches aperture in the house.

Hostess and guest several times made use of this telescope, and on August 22 the baroness remarked to the doctor that she saw a little star in the nebula, a statement which the visitor confirmed. Yet the phenomenon was so faint that both believed the full moon was the in-direct cause, the moonlight overshadowing the fainter portions of the nebula, and permitting only of the visibility of the bright centre. It was not till more than a week after the above date that the existence of the new star was generally recognised, though there is evidence to show that some days previously to August 22 the nebula as a nebula had exhibited unwonted brightness. To none, however, of the observers who noted this fact does it appear that the thought presented itself that they were gazing on a stellar object. At its brightest this new star seems to have reached the 6th magnitude, and there is reason to suppose that when Mr. Ward and the Baroness de Podmaniczky saw the star it was rising to, but had not reached, its maximum brilliancy. The date of this may perhaps be put at August 31. The star then rapidly declined in lustre until the end of September, when it stood at about the loth magnitude. It then further diminished until it became merged in the nebula itself, or rather until its luminosity became lost in the luminosity of the nebula. An interesting question arose as to what were the relations, if any, between the new star and the nebula. A very competent French astronomer named Trouvelot suggested the following reasons for concluding that there was no physical connection between the star and the nebula. There are a multitude of small stars visually scattered all over the nebula. Trouvelot considers these to belong to the Milky Way, of which he traces an extension beyond the nebula, since they increase in number as the Milky Way is approached. They are likewise perfectly sharp and well-defined, which they would not be if they were either in the nebula or behind it. He concludes, therefore, that the nebula lies behind the Milky Way. The well-defined appearance of the new star, and of a small star near it, which he thought was also a new one, seemed to prove that they were both in front of the nebula, and were associated with the Milky Way rather than with the nebula. These surmises, it will be observed, throw no light upon the question why this new star should suddenly have blazed forth and as suddenly have faded away. I must, however, add my testimony to Trouvelot's so far as to say that when I saw the new star myself on September 3, in a 6-inch refractor, I could not refrain from entering in my note-book the thought that " the star had nothing to do with the nebula."

On December 13, 1885, Mr. J. E. Gore in Ireland noticed a new star of the 6th magnitude, reddish in colour, situated some 20' following x1 Orionis. It was found to have a beautiful banded spectrum of Secchi's Type III. Six months later it had diminished to below the 12th magnitude. It afterwards increased again, and is now recognised as a variable going through all its changes of Magnitude in about 12 months. Why the sudden and special increase of its light in December, 1885, cannot be surmised.

There yet remains another new or temporary star for mention, the history of which is extremely interesting. On February 1, 1892, an anonymous postcard was received by Dr. Copeland, the director of the Royal Observatory at Edinburgh, to the effect that a new star of about the 5th magnitude had become visible in the constellation Auriga not far from the star x. It subsequently transpired that the postcard had emanated from a certain Dr. Anderson, an amateur living in Edinburgh, who had discovered the star by the joint use of a small pocket telescope and McCiure's edition of Klein's " Star Atlas." The history of this star during the weeks immediately preceding its dis. covery by Dr. Anderson became known in a very curious way. Professor Pickering of Harvard College, U. S., had recently conceived the idea of " patrolling the heavens" every fine night by means of a small photographic transit instrument which would automatically sweep the meridian in a series of steps of sufficient exposure to photograph 6th magnitude stars, at intervals corresponding to the equatorial breadth of the field. The scheme was well adapted for the detection of strange objects brighter than 6th magnitude stars, and so it resulted that Anderson's star was found on 13 photographs taken between December Io, 1891, and January 20, 1892. As it appeared on all these, which embraced stars down to the 9th magnitude, but was not to be found on the photograph of December 8th, the presumption is that the new star brightened up from below the 9th magnitude between December 8th and December loth. After remaining at about the 4th or 5th magnitude till the end of February, it diminished somewhat rapidly in brightness, and by the end of March had fallen to below the 2th magnitude. Observations were continued at the Lick Observatory in California till April 26th, when bad weather supervened. It was then of the 16th magnitude, so that it may be said to have practically disappeared. In August, however, it had brightened up again to above the loth magnitude, finally subsiding to about the 12th magnitude.

I have dwelt somewhat fully on the socalled " temporary " stars, because the subject is one which seems to open up opportunities of scientific usefulness to the class of persons under whose notice this volume is likely to fall amateurs possessed of small telescopes, or with no telescopes at all, but with many open-air opportunities of becoming familiar with the aspect of the heavens.

It may have been inferred from various remarks made in this chapter that temporary stars, and variable stars, which will form the subject of the next chapter, are so closely associated as almost to imply that all temporary stars are merely variables of long and irregular periods. There is much to support this idea, as also the correlative idea that many of the "missing" stars are also variables not yet recognised to be such. But Kirkwood, an experienced and thoughtful American observer, considers that the theory that temporary stars are long-period variables is unsound : that the suddenness of their apparition, the short duration of their maximum brightness, and the great length of their periods, if they are really periodic, are reasons for regarding them as distinct in their nature from the variable stars properly so-called. It is worthy of notice that there is no known instance of a new star appearing and remaining permanently visible.