The November Meteors
During November 13 and 14 the earth is passing through the region along which lies the course of the family of meteors called the Leonides, sometimes familiarly known as the November meteors. When at this time of the year the meteor region thus traversed by the earth is densely strewn with meteors, there occurs a display of falling stars, one of the most beautiful, and, rightly understood, one of the most remarkable of all celestial phenomena. Of old, indeed, when it was supposed that these meteors were purely meteorological phenomena, they were not thought specially interesting objects. They were held by some as mere weather-portents. It was only when a storm of wind was approaching, vento impendente, according to Virgil, that a shower of meteors was to be seen. Gross ignorance, indeed, has given to showers of falling stars an interest surpassing even that which has become attached to them through the discoveries of modern science, for they have been regarded as portending the end of the world. The shower of November 13, 1833, which was seen in great splendour in America, frightened the negroes of the Southern States nearly out of their wits. A planter of South Carolina relates that he was awakened by shrieks of horror and cries for mercy from 600 or 700 negroes. When he went out to see what was the matter, he found the negroes prostrate on the ground, ‘some speechless, some with bitterest cries imploring God to spare the world and them.’ There is, however, a grandeur in the interpretation placed by modern science upon these beautiful displays which dwarfs into littleness even such ideas as have been suggested by the terrors of superstition. We perceive that meteors are not mere terrestrial phenomena, nor of brief existence. They speak to us of domains in space compared with which the volume of our earth—nay, even the volume of the sun himself—is a mere point: of time-intervals compared with which the millions of years spoken of by geologists appear but as mere seconds.
The special meteor family whose track the earth crosses on November 13-14 forms a mighty ellipse round the sun, extending more than 19 times farther from him than the track of our earth, which yet, as we know, lies more than 92,000,000 miles from the sun. Along this tremendous orbit the meteors speed with planetary but varying velocity, crossing the track of our earth with a velocity exceeding by more than a third her own swift motion of about 19 miles in every second of time. Coming down somewhat aslant, but otherwise meeting the earth almost full tilt, the meteors rush into our air at the rate of more than 40 miles per second. They are so intensely heated as they rush through it that they are turned into the form of vapour, insomuch that we never make acquaintance with the members of this particular meteoric family in the solid form. In this respect they resemble the greater number of our meteoric visitants. It is, indeed, a somewhat fortunate circumstance for us that this is so, for if Professor Newton, of Yale College (United States), is right in estimating the total number of meteors, large and small, which the earth encounters per annum at 400,000,000, it would be rather a serious matter if all or most of these bodies were not warded off. The least of them, even though a mere grain perhaps in weight, would yet, arriving with planetary velocity exceeding a hundredfold or more the velocity of a cannon-ball, prove an awkward missile if it struck man or animal. But the air effectually saves us from all save a few fire-balls which are large enough to remain in great part solid until they actually strike the earth itself.
The importance of the meteors in the planetary system will be recognised when we remember that the November group alone extends along its oval course in one complete system of meteors for a length of more than 1,700 millions of miles, with an average thickness of about a million miles (determined by noting the average time occupied by the earth in passing through the system on November 13-14), and an unknown cross breadth which probably does not fall short of three or four millions of miles. Other systems are, no doubt, far more important, for it has been found that meteors follow in the track of comets. Now the November meteors follow in the track of a comet (Tempel’s comet of 1866), which was so small when last favourably placed for observation that it escaped detection by the naked eye. If so small a comet as this is followed by so large a meteoric system, in which also meteors are strewn so richly that during the passage of the earth through it, tens of thousands of meteors have been counted, how vast must be the numbers and how large probably the individual bodies following in the track of such splendid comets as Newton’s, Donati’s (1858), the comets of 1811, 1847, 1861, and others! For it should be remembered that we become cognisant of the existence of a meteoric system only when the earth threads its way through one, when those which she encounters may become visible as falling stars if it so chances that she encounters them on the dark or night half of her surface. But the earth is far smaller compared with a system like the November meteor-flight than a rifle-ball compared with the largest flight of birds ever yet seen. Such a ball fired into a very dense and widely extending flock of birds might encounter here and there along its course some five or six birds—not one in 10,000, perhaps, of the entire flight; and if the flock continued flying with unchanging course, a hundred rifle balls might be fired through it without seemingly reducing its numbers. Our earth has passed hundreds of times through the November meteor system, yet its meteoric wealth has scarcely been reduced at all, so exceedingly minute is the track of the earth through the meteor system compared with the extension of the system itself. The region through which the earth has passed is less than a billionth part of the entire region occupied by the system. But the November system is but one among several hundreds through which the earth passes—in other words, the systems which chance to be traversed by that mere thread-like ring in space traversed each year by the earth, are not a millionth, not a billionth, of the total number of such systems. It will be conceived, therefore, that the total amount of meteoric matter, travelling on orbits of all degrees of eccentricity and extension from the sun and inclined at all angles to the general plane of the solar system, must be enormously great. The idea once advanced by an eminent astronomer that the total quantity of unattached matter, so to speak, existing within the solar domain must be estimated rather by pounds than by tons is now altogether exploded. It would be truer to say that the totality of matter thus freely travelling around the sun must be estimated by billions of tons rather than by millions.
Whether it is likely that there will be a display of meteors to-night (or, rather, to-morrow morning), is a question to which most astronomers would be disposed, we believe, to reply definitely in the negative. The display of November 13-14, 1866, was very brilliant; that of 1867 (best seen in the United States) was almost equally so; but successive showers steadily diminished. In other words, the part of the system crossed by the earth in 1866 and 1867 was very rich, but the part which she crossed afterwards (the rich part having passed far on towards the remote aphelion of the system outside the orbit of Uranus) was less rich. For the last few years very few November meteors have been seen, though the few stragglers which have been seen, and have been identified as belonging to the family by their paths athwart the star-depths, have been almost as interesting to astronomers as the showers of such bodies seen in 1799, 1833, 1866, and 1867. But it is not altogether impossible that in the small hours ‘ayont the twal’ to-morrow morning a shower of meteors may be seen. For Schiaparelli (the Italian astronomer who first started the ideas which led when properly followed up to the discovery of the relations existing between meteors and comets) asserts that it has happened before now that the November meteors have appeared in great numbers in years lying midway between the times of maximum display. These times are separated on the average by about 33¼ years. Thus, in 1799, there was a great display of November meteors, a shower rendered specially celebrated by Humboldt’s description. In 1833 there was another, the display which so terrified the negroes of South Carolina, but more interesting scientifically as described by Arago. In 1866 the shower again attained its maximum splendour, though the display of 1867 was little inferior. It will not be till 1899 that another great shower of November meteors may be confidently looked for. But if Schiaparelli be right, it is quite possible that there may be a shower this year, due to some scattered flight of the November meteors which, delayed accidentally (through some special perturbation) many hundreds of years ago, has come in the course of ages to travel nearly half a circuit behind the richest part of the system, the ‘gem of the meteor-ring,’ as it has been poetically called. Even, however, though no display of November meteors should be seen, yet the recognition of even a few scattered stragglers would be exceedingly interesting to astronomers. A single meteor seen to-night which could be regarded as certainly belonging to the November system would suffice to show the possibility that a whole flight of the November meteors might travel at a similar distance behind the main body. It would be more easy, however, to identify two such meteors than one, six than two, and a score than half-a-dozen. The only way in which a meteor can be questioned, so to speak, respecting the family it belongs to, is by noting its path across the sky. If this path tends directly from the constellation Leo (however remote Leo may be from the part of the heavens traversed by the meteor), the chances are that the meteor is a Leonid, or one of the November family. If the path tends from that particular part of the constellation Leo (near the end of the curved blade of the so-called Sickle in Leo), the probability of the meteor being a Leonid is increased. If two or more meteors are seen to-morrow morning (after 12.30) which both tend from the Sickle in Leo, even though they seem to tend in opposite directions, the chances are yet greater that they are travelling in parallel paths along the track of the November meteors, but some 2,000 million miles behind the main body. Should the number mount up to a score or so, the conclusion would be, to all intents and purposes, certain; and the possible occurrence of even a shower of Leonids at a time midway between the customary maxima of the meteoric displays would be placed beyond question.
We must, however, admit that it seems less likely there will be anything like a display of Leonids to-night than that patient observers may be able to identify a few of these bodies, and thus—though by observations of a less attractive kind—to advance our knowledge of this interesting system. Far more likely is it that towards the end of the month there will be a display of meteors belonging to another and an entirely distinct family, a family scarcely less worthy to be called November meteors par excellence, but actually rejoicing in the classically unsatisfactory name of Andromeds.