CHAPTER FOUR
COMETS IN DISTRESS
“Thou comest whence no mortal seer can know, Thou goest whither nothing human dreams.” —ANON.
Until the photographic eyes of Science detected the peculiarities of comets, and mathematicians calculated with unerring accuracy their comings and goings, they were looked upon, as we have already seen, with more or less suspicion and dread. Nowadays, we know that these “airy nothings,” as Sir John Herschel termed them, have been unjustly maligned. Were they given the power of speech, they could a tale unfold of adventurous thrills and overwhelming disasters encountered during their voyages in space, far exceeding in interest any story of terrestrial adventure. It would take the pen of a Jules Verne and an author gifted with his vivid imagination to describe the erratic career of a comet.
Take for instance the tragic fate of the headless comet of 1887, which was described by Dr. Thomé of the Cordoba University as:
“a beautiful object with a narrow, straight, sharply defined graceful tail over fifty degrees long. It was shining with a soft starry light against a dark sky, beginning apparently without a head, and gradually widening and fading as it extended upwards.”[4]
Now the popular idea of a well-regulated comet is a star with a tail, but a tail without an accompanying star seems preposterous, yet a headless comet this object remained as viewed with the naked eye. The why and the wherefore of the tragedy is unknown, and whether it ever had a head and what became of it remains one of the many unsolved problems of the sky.
Still more remarkable is the career of the famous comet of Biela, from its first appearance as viewed by mortal eyes on March 8, 1772, until its final disappearance, a century later, in a veritable blaze of celestial fireworks. Its story reads like a novel, and is far more fascinating because it is fact and not fiction. The hero is a faint, insignificant-looking object which was discovered by Montaigne of Limoges, already referred to as the comet-hunter who so indiscreetly found the thirteenth comet for which his colleague Messier was industriously searching. Little did Montaigne guess that this foggy speck of light which was so faint that it could only be seen with the aid of his small telescope would one day attract worldwide attention. Its nondescript appearance, with a tail only one-eighth the diameter of the moon, made it apparently scarcely worthy of more than passing notice. Had Montaigne concentrated his efforts on finding out its peculiarities and tracing its path, his name would have been forever connected with the little wanderer, instead of being entered in the annals of astronomy as merely the first to see it.
The introductory chapter in its story is connected with a letter written by Montaigne to the director of the observatory at Paris, announcing his discovery. This arrived in time to give the astronomers an opportunity for seeing the comet three or four times ere it vanished on its way outward bound. Little more was thought of the celestial visitor until it was glimpsed again thirty-three years later, in November, 1805, by Pons, who, as we have already seen, shared honors with Messier and Montaigne in the “eccentric vocation” of comet-hunting. The comet remained visible in the northern heavens for only a month, when it sank below the horizon and was no longer visible to observers in the northern hemisphere.
However, on this occasion the comet came very close to the earth, for we are told that it was visible to the naked eye, even in the strong twilight. Then it remained hidden from view until twenty years later, when it was again rediscovered, this time by an Austrian officer named Biela, in February, 1826. He was determined that the wily object should not be lost sight of again, as far as its orbit was concerned, and by means of careful observations and calculations he was enabled to announce that it was traveling along the same route as the comet seen by Montaigne in 1772, and that seen by Pons in 1805. Therefore, he concluded that it was one and the same comet, and predicted its return in 1832.
However, when it was announced by the great French astronomer, Arago, that the comet at this return would cross the orbit of the earth, widespread was the consternation among those who did not know what an orbit was. Possibly, imagining that it was something tangible, we can picture them looking at one another in dismay, and whispering in awed tones, “Does this mean the comet will hit the earth, and if so what will happen to us?” A possible collision with the comet was an alarming thought to the ignorant and superstitious, and the fear caused by Arago’s announcement was so great that it resulted in the first of the many comet-scares. People in dread of the threatened calamity sold their goods and chattels, and thronged the churches as a fit preparation for the end of the world. There they awaited the expected crash and doubtless were surprised when nothing unusual happened. The earth still continued to roll on its appointed path, without jolt or jar to disturb the “even tenor of its way.” The nervous gave a sigh of relief when the comet withdrew once more into the obscurity of space, and those who had parted with their belongings must have felt somewhat annoyed.
The so-called devout astrologers who had made use of Arago’s announcement to their own advantage, when upbraided by those whom they had warned, did a skillful kind of “hedging,” by stating that events announced by a comet might be postponed for one or more periods of forty years or even as many years as the comet had appeared days. Consequently, one which had appeared for six months would not produce any effect, evil or otherwise, for 180 years.[5] Thus these wise soothsayers allowed a wide margin for possible results.
To give an idea of the filmy structure of the comet, the cause of such unnecessary alarm, it was described by Sir John Herschel, who observed it on September 23, 1832, as a round hazy-looking object without a tail. It was moving in the direction of a small group of faint stars, which were undimmed when overtaken by the comet, so that it resembled a fog-like mist sprinkled with stars, this veil of cometary matter being estimated by Herschel as fifty thousand miles thick. Yet, only a month later, the remote prospect of a collision with this celestial cobweb caused a panic in Europe!
The comet was first seen on August 23, 1832, but owing to its excessive faintness was not generally observed till two months later, when at its nearest to the sun. This occurred during the month of November, within twelve hours of the time predicted by an astronomer named Santini. At its next return, in 1839, the comet was not well placed for observation, as it was too near the sun, and therefore lost in the glare of its light. As computations had shown that the comet was traveling in an orbit requiring six and two-thirds of a year, it was due to return in 1845.
The first to bid it welcome was an astronomer at Rome named De Vico, on November 28 of that year. Two days later it was observed by Dr. Gallé at Berlin, but it was not generally seen until December. It appeared as a single comet on November 28, but on December 19 it was seen distinctly pear-shaped, and ten days later it amazed all observers by splitting in two. This marvelous transformation was first detected by two Americans, Mr. Herrick, then librarian at Yale College, and Mr. Francis Bradley, a clerk in the New Haven City Bank. The two were watching the comet on January 29, 1845, taking turns in looking through a telescope which had been erected in the Athenæum tower.
Suddenly one of the observers exclaimed that he could see a small comet accompanying the larger one, and we can imagine his friend making some remark concerning defective eyesight. However, when both saw the duplicity of the comet, all doubts were dispersed. But what did it mean? Had the comet a satellite, just as the earth has its accompanying moon, or had the comet actually split in two? However, the twin comets were seen two weeks later by Lieutenant Maury and Professor Hubbard at Washington, D. C., and two days later it came within the ken of European astronomers. Incidentally, three weeks before the twin comets were observed, Mr. J. Russell Hind (England) noticed a peculiar lump near the upper part of the nucleus of the main comet, which may be regarded as the first symptom indicating that something was amiss.
On January 15, Professor Challis, then director of Cambridge Observatory (England), had his suspicions aroused when he saw the complete severance of the little comet from the big one, and the description of his experience is best given in a letter he wrote to the president of the Royal Astronomical Society:
“On the evening of January 15, when I sat down to observe it [Biela’s comet], I said to my assistant, ‘I see _two_ comets.’ However, on altering the focus of the eyeglass and letting in a little illumination, the smaller of the two comets appeared to resolve itself into a minute star, with some haze about it. I observed the comet that evening but a short time, being in a hurry to proceed to observations of the new planet.”
Presumably he here refers to the search for Neptune. Alas! had he but given his whole attention to that task, instead of dispersing his energy—as it were—by pursuing a flimsy comet, England might have been acknowledged as first in the actual discovery of that planet.
Resuming his observations of the comet on January 23, Professor Challis again saw two comets, but clouds hid them from view for the next half-hour, and when they had cleared away he was convinced that the comets had moved during the interval. This suspicion was afterward confirmed, and, moreover, Professor Challis found that they had moved in unison, retaining their relative positions meanwhile. He wondered what could be the meaning of this strange procedure, and whether they were two independent comets, a double comet, or that his glass was deceiving him.
“But I never heard of such a thing,” wrote Professor Challis. “Kepler supposed that a certain comet separated in two, and for this Pingré said of him, ‘_Aligreando bonus dormitat Homerus._’ I am anxious to know whether other observers have seen the same thing.”
In a subsequent letter he shows by his remarks that “the two comets are not only apparently, but really near each other, and that they are physically connected.”[6]
The comets continued traveling along in this sociable manner for four months, at an almost unvarying distance of about 165,000 miles, each developing meanwhile a very bright nucleus and diminutive tail half a degree in length, or one tenth the distance separating the pointers in Ursa Major. Sometimes one comet would be devoid of a tail, sometimes the other, so that one might almost imagine the tail exchanging owners, for the comets were rarely both adorned therewith at the same time.
During the latter part of February, Lieutenant Maury, at Washington, D. C., saw an arc of light extending from the large comet to the small one, forming a sort of bridge between the two, this occurring when the small comet was at its brightest. When the large comet had regained its superiority it threw out new rays, which gave it the appearance of having three tails, each adjacent tail making an angle of 120 degrees with its neighbor, one of the tails being the bridge to the new comet. This produced the effect of an arch in the heavens, through which the stars were seen to pass.
One can imagine messages passing to and fro along this bridge of light between the twin comets, and a possible farewell as they drifted further apart. At their return in August, 1852, they were separated by about one million five hundred thousand miles, and as so often happens in the case of twins it was impossible to tell which was which. The comets were not seen at their next return, in May, 1859, because they were lost in the glare of sunlight, for the same reason that we are unable to see stars in the daytime.
At the next expected visit when the comets were looked for, in January, 1866, they were nowhere to be seen. What had happened in the interval no one knows, but in 1872 the whole astronomical world was startled by a telegram from an astronomer named Klinkerfues of Göttingen, on November 30, to Pogson, the government astronomer at Madras, which read as follows:
Biela touched earth on 27th, search near Theta Centauri.
Accordingly, a search was made, with the extraordinary result that a comet _was_ found, but not _the_ comet. Observations were obtained of it on December 2 and 3, but bad weather and the advance of twilight made further search impossible. When the track of the new comet, for such it proved to be, was eventually followed, it was found to be moving along a different route from the one previously followed by the comet of Biela. Nevertheless, by a remarkable coincidence it happened to be passing by or near the place where this comet was wont to wander, until he took unto himself a companion comet, which seems to have led him astray.
To be lost is interesting, especially for a comet, when one considers the vast expanse of highways and byways in starland, but the climax of the tragedy in connection with this special comet was not reached until its orbit crossed that of the earth on November 27, 1872. On that eventful night the sky seemed to be literally ablaze with meteors, which fell in swarms and showers of dazzling gleams of light, the downpour lasting from seven o’clock in the evening until one o’clock next morning, the maximum being attained at nine o’clock. We are told that the total number observed in England was estimated at a hundred and sixty thousand. They all came from the same part of the sky, radiating from a point near the beautiful double star Gamma in the constellation of Andromeda. But what was the meaning of the display? Had it been caused by an encounter of the earth with the scattered fragments of the lost comet? It certainly could not have had any connection with the comet itself, which, providing it still existed, had passed that way three months before. It was more likely the débris of its train scattered along its path after its breaking up in 1846.
There seems to be no doubt of the identity of this swarm of meteors with the comet of Biela, for on November 27, 1885, a similar encounter took place, providing a magnificent display of meteors observed all over Europe, just at the moment when the earth was due at a crossing in the former path of the comet. On that same evening, a piece of meteoric iron fell at Mazapil, in northern Mexico, during the course of the shower, and according to Professor Young, “the coincidence may be accidental, but is certainly interesting. Some high authorities speak confidently of this piece of iron _as a piece of Biela’s comet itself_.” (_General Astronomy_, C. A. Young.)
In 1892 and 1898, when the earth again crossed the former path of the comet, a similar display occurred, though on a minor scale, and some of the scattered cometary fragments may still be looked for on the evenings from November 17 to 27. They are recognizable from their slow motion, short trains, and from the fact that they all radiate from the second-magnitude star Gamma in Andromeda. (Incidentally, this is the star so charmingly dealt with by Dr. Holmes, in the _Poet at the Breakfast Table_, really the astronomer of the breakfast table, as suggested by conversations and correspondence between my father and Oliver Wendell Holmes.)
The star Gamma in Andromeda is easily located, as it is almost overhead between the dates November 17–27, at a convenient hour in the evening. It is in a line with Epsilon, the star at the left-hand corner of the W-shaped group in the constellation, Cassiopeia, and with Polaris, the Pole Star. The meteors radiating from this point are variously referred to as the Andromedæ, Andromedids, and the Bielids, on account of their supposed connection with the Comet of Biela. As a matter of fact it matters little what they are called, as long as we know their appearance and when and where to look for them. They may be looked upon as supplementary to the story of the comet, and possibly some of the particles may eventually find a resting-place on planet earth.
According to Dr. Crommelin of the Greenwich Observatory:
“the career of a comet may be said to be over when its meteors have lost all their gas, or when they have been scattered by perturbations over so wide a space that its unity and visibility are lost. These disrupting causes are most effective when a comet is fairly near the sun; therefore the oftener that a comet approaches the sun, the shorter the period of its existence as a comet. I think, therefore, that we can ascribe the great prevalence of long-period comets to the principle of the survival of the fittest.”
Long-period comets are those which sometimes require hundreds of years before they return sunward, as, for instance, Donati’s comet with its period of about two thousand years. Others of short period, like Encke’s comet, are regular visitors to the sun, returning after a short interval of a few years along a well-known path. Once upon a time they may have been long-period comets, which have had their paths restricted, owing to the strong attractive pull of the giant planets Jupiter, Saturn, Uranus, and Neptune. As a result of the disturbances (or perturbations, as they are technically called) thus caused, according to the so-called capture theory, Jupiter has annexed fifty comets, including the Comet of Biela. Uranus and Saturn, according to the same theory, own a limited family of two, while Neptune has four, including Halley’s famous comet. Its least distance from the sun is 56 million miles at its point of nearest approach, and 3,200 million miles when at the opposite end of its orbit. But the great majority of these strange bodies appear to travel in parabolas, open curves leading from infinite space to and around the sun, and thence back into the region of the fixed stars.
There is a notable instance of a comet traveling about the sun in an immense ellipse, but, like the moth, hovering around a flame which finally causes its destruction, this comet returned once too often to the neighborhood of the giant planet Jupiter, and in an encounter between a large and a small body, the latter usually comes to grief. Its path was curtailed at first, and subsequently it was shunted on to another line. Jupiter, acting as pointsman on the cometary railway, is suspected of opening the branch of the ellipse along which the comet had formerly traveled in peace and quiet, with the result that it was ignominiously sidetracked and sought for in vain.
The comet was first discovered in June, 1770, by Messier, who described it as a rather insignificant object without a tail, but resembling a nebula with a star-like nucleus. Early in July it had greatly increased in size, the nucleus and surrounding haze extending over a space more than five times the diameter of the moon. At this time it came very near the earth, remaining visible until October, when it grew small and faint, and finally faded away. Meanwhile, astronomers did their best to determine its path, notably Mr. Lexell, of the Academy of Sciences at St. Petersburg. He became so interested in clearing up the past history of this quaint little comet, that it is usually referred to as Lexell’s comet. He came to the conclusion that the comet of 1770 required five years and seven months for its elliptic tour, but he was such a long time in getting at this result, that by the time he obtained it in 1778 the comet was two years overdue. Messier made a careful search for it, but without success.
Lexell was of the opinion that at the end of May, 1776, the comet came so close to Jupiter that the attractive pull of that planet was three times greater than that of the sun. When a comet rushes around the sun it has to go full speed ahead, so as to resist being drawn upon its surface, but as it recedes from the danger zone it gradually slackens its pace, with the result that by the time it is crossing the orbit along which Jupiter travels, it is going at reduced speed. Probably Jupiter was not far from the part of its orbit crossed by the comet in 1776, with the result that the unfortunate wanderer was exposed for a longer period to the powerful attraction of the giant planet. This may have caused an important change in the comet’s path, with the result that it escaped from what has been termed the _sphere of activity_ early in October, 1779.
At this period, according to Lexell, the comet was moving in an ellipse with a period of more than sixteen years, and at such a distance there would be no hope of our seeing it again. He finally considered the comet of 1770 as definitely lost. However, when Brooks, the famous comet-hunter of Geneva, New York, discovered a comet in 1889, which is known as Comet 1889 V, as it was the fifth comet discovered that year, it was supposed to be the long-lost Lexell comet of 1770. For that reason it is known as the Lexell-Brooks comet.
Previous to 1886, the comet discovered in 1889 was traveling around the sun in an immense ellipse, taking it out beyond the planet Uranus. Around and around the sun it went, as a moth flutters around a lamp, until in the year 1886 it came under the magic spell of Jupiter. Unable to resist this planet’s persuasive influence, the path of the comet was reduced to a smaller one requiring only seven years for its completion. Apparently on this occasion the comet passed too near Jupiter for safety, and was reduced to four fragments in consequence. When it approached the sun in 1889, and was discovered by Brooks, it may probably have been one of the four fragments; at any rate, this is the opinion of Dr. Charles Lane Poor, of New York, who made a careful and most exhaustive study of the comet and its eccentricities. It remained visible with telescopes of ordinary power until March, 1890, after which date it could only be seen with the great telescope at the Lick Observatory, at Mount Hamilton, California. With this magnificent instrument Professor Barnard followed the comet until January, 1891.
The path of its next return was calculated so accurately that when it was rediscovered on June 20, 1896, by Javelle, it was seen within a distance less than one quarter the diameter of the moon from its predicted place. By this time the comet had grown fainter, as though enfeebled by its long wanderings and the vicissitudes of its career, and it remained visible for only a few months, finally disappearing in February, 1897. For a third time the comet came near enough for us to see it, and this occurred during the summer of 1903, when it remained visible until the following January. It was then so faint, it could only be observed with the largest telescopes. The future of the comet seems as likely to be as interesting as its past.
“Unless it become wholly disintegrated by the pulling and hauling of the sun and planets, it will be seen again in 1910, and yet again in 1917,” wrote Dr. Poor in 1908, but as a matter of fact it was not observed on either occasion. Dr. Poor also predicted that early in 1921 it would again come into close approach with Jupiter, “and beyond that point its history cannot be predicted. This collision will probably end its story as far as the earth is concerned, for it will undoubtedly be still further broken up, and its orbit may be so changed that it will never afterwards be seen.” And we must leave it with this unsatisfactory conclusion, as it did not reappear in 1921, and nothing more has been seen or heard of this comet. By now (1925) it may be merely a derelict in space, at the mercy of any disturbing planet it may happen to pass on the way.
These instances give some idea of the dangers to which comets are subjected as they drift like frail barks on the ocean of space. Whence they have come and whither they vanish, no one knows, but it has been suggested that there is a home of comets. This has been described as a shell of nebulous matter accompanying the sun and planets, though at a distance some thousands of times greater than that of the earth from the sun, yet much closer than the nearest star. “However, we have no direct evidence of any such comet-dropping envelope,” according to Professor C. A. Young.
Yet supposing it does exist, we see in imagination baby comets cradled therein in nebulous mist until they are able to take care of themselves. Then they are presumably launched forth on their perilous career, as they make their way towards their ruler, the sun, to pay their respects. Woe betide them should they cross the path of one of the giant planets at an inauspicious moment, or approach too near the sun, which would prove equally disastrous.