Astronomical Curiosities: Facts and Fallacies

According to Humboldt, Chladni states that a Franciscan monk was killed by the fall of an aërolite at Milan in the year 1660.246 Humboldt also mentions the death by meteoric stones of a monk at Crema on September 4, 1511, and two Swedish sailors on board ship in 1674.247

It is a curious fact that, according to Olbers, “no fossil meteoric stones” have ever been discovered.248 Considering the number which are supposed to have fallen to the earth in the course of ages, this fact seems a remarkable one.

On May 10, 1879, a shower of meteorites fell at Eitherville, Iowa (U.S.A.). Some of the fragments found weighed 437, 170, 92½, 28, 10½, 4 and 2 lbs. in weight. In the following year (1880) when the prairie grass had been consumed by a fire, about “5000 pieces were found from the size of a pin to a pound in weight.”249

According to Prof. Silvestria of Catania, a shower of meteoric dust mixed with rain fell on the night of March 29, 1880. The dust contained a large proportion of iron in the metallic state. In size the particles varied from a tenth to a hundredth of a millimetre.250

It is sometimes stated that the average mass of a “shooting star” is only a few grains. But from comparisons with an electric arc light, Prof. W. H. Pickering concludes that a meteor as bright as a third magnitude star, composed of iron or stone, would probably have a diameter of 6 or 7 inches. An average bright fireball would perhaps measure 5 or 6 feet in diameter.251

In the Book of Joshua we are told “that the Lord cast down great stones from heaven upon them unto Azekah, and they died” (Joshua x. 11). In the latter portion of the verse “hailstones” are mentioned, but as the original Hebrew word means stones in general (not hailstones), it seems very probable that the stones referred to were aërolites.252

The stone mentioned in the Acts of the Apostles, from which was found “the image which fell down from Jupiter” (Acts xix. 35), was evidently a meteoric stone.[253]

The famous stone in the Caaba at Mecca, is probably a stone of meteoric origin.[253]

I“Stones from Heaven! Can you wonder,You who scrutinize the Earth,At the love and venerationThey received before the birthOf our scientific methods?II“Stones from Heaven! we can handleFragments fallen from realms of Space;Oh! the marvel and the mystery,Could we understand their placeIn the scheme of things created!III“Stones from Heaven! With a mightyComet whirling formed they part?Fell they from their lofty stationLike a brilliant fiery dart,Hurl’d from starry fields of Night?”253

CHAPTER XIII

The Zodiacal Light and Gegenschein

According to Gruson and Brugsch, the Zodiacal Light was known in ancient times, and was even worshipped by the Egyptians. Strabo does not mention it; but Diodorus Siculus seems to refer to it (B.C. 373), and he probably obtained his information from some Greek writers before his time, possibly from Zenophon, who lived in the sixth century B.C.254 Coming to the Christian era, it was noticed by Nicephorus, about 410 B.C. In the Koran, it is called the “false Aurora”; and it is supposed to be referred to in the “Rubáiyát” of Omar Khayyam, the Persian astronomical poet, in the second stanza of that poem (Edward Fitzgerald’s translation) —

“Dreaming when Dawn’s Left Hand was in the Sky,255I heard a voice within the Tavern cry,Awake, my Little ones, and fill the Cup,Before Life’s Liquor in its Cup be dry.”

It was observed by Cassini in 1668,256 and by Hooke in 1705. A short description of its appearance will be found in Childrey’s Britannia Baconica (1661), p. 183.

The finest displays of this curious light seem to occur between the middle of January and the middle of February. In February, 1856, Secchi found it brighter than he had ever seen it before. It was yellowish towards the axis of the cone, and it seemed to be brighter than the Milky Way in Cygnus. He described it as “un grande spectacle.” In the middle of February, 1866, Mr. Lassell, during his last residence in Malta, saw a remarkable display of the Zodiacal Light. He found it at least twice as bright as the brightest part of the Milky Way, and much brighter than he had previously seen it. He found that the character of its light differed considerably from that of the Milky Way. It was of a much redder hue than the Galaxy. In 1874 very remarkable displays were seen in the neighbourhood of London in January and February of that year; and in 1875 on January 24, 25, and 30. On January 24 it was noticed that the “light” was distinctly reddish and much excelled in brightness any portion of the Milky Way.

Humboldt, who observed it from Andes (at a height of 13,000 to 15,000 feet), from Venezuela and from Cumana, tells us that he has seen the Zodiacal Light equal in brightness to the Milky Way in Sagittarius.

As probably many people have never seen the “light,” a caution may be given to those who care to look for it. It is defined by the Rev. George Jones, Chaplain to the “United States’ Japan Expedition” (1853-55), as “a brightness that appears in the western sky after sunset, and in the east before sunrise; following nearly or quite the line of the ecliptic in the heavens, and stretching upwards to various elevations according to the season of the year.” From the description some might suppose that the light is visible immediately after sunset. But this is not so; it never appears until twilight is over and “the night has fully set in.”

The “light” is usually seen after sunset or before sunrise. But attempts have recently been made by Prof. Simon Newcomb to observe it north of the sun. To avoid the effects of twilight the sun must be only slightly more than 18° below the horizon (that is, a little before or after the longest day). This condition limits the place of observation to latitudes not much south of 46°; and to reduce atmospheric absorption the observing station should be as high as possible above the level of the sea. Prof. Newcomb, observing from the Brienzer Rothorn in Switzerland (latitude 46° 47′ N., longitude 8° 3′ E.), succeeded in tracing the “light” to a distance of 35° north of the sun. It would seem, therefore, that the Zodiacal Light envelops the sun on all sides, but has a greater extension in the direction of the ecliptic.257 From observations at the Lick Observatory, Mr. E. A. Fath found an extension of 46° north of the sun.258

From observations of the “light” made by Prof. Barnard at the Yerkes Observatory during the summer of 1906, he finds that it extends to at least 65° north of the sun, a considerably higher value than that found by Prof. Newcomb.259 The difference may perhaps be explained by actual variation of the meteoric matter producing the light. Prof. J. H. Poynting thinks that possibly the Zodiacal Light is due to the “dust of long dead comets.”260

From careful observations of the “light,” Mr. Gavin J. Burns finds that its luminosity is “some 40 or 50 per cent. brighter than the background of the sky. Prof. Newcomb has made a precisely similar remark about the luminosity of the Milky Way, viz. that it is surprisingly small.” This agrees with my own observations during many years. It is only on the finest and clearest nights that the Milky Way forms a conspicuous object in the night sky. And this only in the country. The lights of a city almost entirely obliterate it. Mr. Burns finds that the Zodiacal Light appears “to be of a yellowish tint; or if we call it white, then the Milky Way is comparatively of a bluish tint.” During my residence in the Punjab the Zodiacal Light seemed to me constantly visible in the evening sky in the spring months. In the west of Ireland I have seen it nearly as bright as the brightest portions of the Milky Way visible in this country (February 20, 1890). The “meteoric theory” of the “light” seems to be the one now generally accepted by astronomers, and in this opinion I fully concur.

From observations made in Jamaica in the years 1899 and 1901, Mr. Maxwell Hall arrived at the conclusion that “the Zodiacal Light is caused by reflection of sunlight from masses of meteoric matter still contained in the invariable plane, which may be considered the original plane of the solar system.”261 According to Humboldt, Cassini believed that the Zodiacal Light “consisted of innumerably small planetary bodies revolving round the sun.”262

The Gegenschein, or Counter-glow. – This is a faint patch of light seen opposite the sun’s place in the sky, that is on the meridian at midnight. It is usually elliptical in shape, with its longer axis lying nearly in the plane of the ecliptic. It seems to have been first detected by Brorsen (the discoverer of the short-period comet of 1846) about the middle of the nineteenth century. But it is not easy to see, for the famous Heis of Münster, who had very keen eyesight, did not succeed in seeing it for several years after Brorsen’s announcement.263 It was afterwards independently discovered by Backhouse, and Barnard.

Prof. Barnard’s earlier observations seemed to show that the Gegenschein does not lie exactly opposite to the sun, but very nearly so. He found its longitude is within one degree of 180°, and its latitude about 1°·3 north of the ecliptic.264 But from subsequent observations he came to the conclusion that the differences in longitude and apparent latitude are due to atmospheric absorption, and that the object really lies in the ecliptic and exactly opposite to the sun.265

Barnard finds that the Gegenschein is not so faint as is generally supposed. He says “it is best seen by averted vision, the face being turned 60° or 70° to the right or left, and the eyes alone turned towards it.” It is invisible in June and December, while in September it is round, with a diameter of 20°, and very distinct. No satisfactory theory has yet been advanced to account for this curious phenomenon. Prof. Arthur Searle of Harvard attributes it to a number of asteroids too small to be seen individually. When in “opposition” to the sun these would be fully illuminated and nearest to the earth. Its distance from the earth probably exceeds that of the moon. Dr. Johnson Stoney thinks that the Gegenschein may possibly be due to a “tail” of hydrogen and helium gases repelled from the earth by solar action; this “tail” being visible to us by reflected sunlight.

It was observed under favourable circumstances in January and February, 1903, by the French astronomer, M. F. Quénisset. He found that it was better seen when the atmosphere was less clear, contrary to his experience of the Zodiacal Light. Prof. Barnard’s experience confirms this. M. Quénisset notes that – as in the case of the Zodiacal Light – the southern border of the Gegenschein is sharper than the northern. He found that its brightness is less than that of the Milky Way between Betelgeuse and γ Geminorum; and thinks that it is merely a strengthening of the Zodiacal Light.266

A meteoritic theory of the Gegenschein has been advanced by Prof. F. R. Moulton, which explains it by light reflected from a swarm of meteorites revolving round the sun at a distance of 930,240 miles outside the earth’s orbit.

Both the Zodiacal Light and Gegenschein were observed by Herr Leo Brenner on the evening of March 4, 1896. He found the Zodiacal Light on this evening to be “perhaps eight times brighter than the Milky Way in Perseus.” The “Gegenschein distinctly visible as a round, bright, cloud-like nebula below Leo (Virgo), and about twice the brightness of the Milky Way in Monoceros between Canis Major and Canis Minor.”267

Humboldt thought that the fluctuations in the brilliancy of the Zodiacal Light were probably due to a real variation in the intensity of the phenomenon rather than to the elevated position of the observer.268 He says that he was “astonished in the tropical climates of South America, to observe the variable intensity of the light.”

CHAPTER XIV

The Stars

Pliny says that Hipparchus “ventured to count the stars, a work arduous even for the Deity.” But this was quite a mistaken idea. Those visible to the naked eye are comparatively few in number, and the enumeration of those visible in an opera-glass – which of course far exceed those which can be seen by unaided vision – is a matter of no great difficulty. Those visible in a small telescope of 2¾ inches aperture have all been observed and catalogued; and even those shown on photographs taken with large telescopes can be easily counted. The present writer has made an attempt in this direction, and taking an average of a large number of counts in various parts of the sky, as shown on stellar photographs, he finds a total of about 64 millions for the whole sky in both hemispheres.269 Probably the total number will not exceed 100 millions. But this is a comparatively small number, even when compared with the human population of our little globe.

With reference to the charts made by photography in the International scheme commenced some years ago, it has now been estimated that the charts will probably contain a total of about 9,854,000 stars down to about the 14th magnitude (13·7). The “catalogue plates” (taken with a shorter exposure) will, it is expected, include about 2,676,500 stars down to 11½ magnitude. These numbers may, however, be somewhat increased when the work has been completed.270 If this estimate proves to be correct, the number of stars visible down to the 14th magnitude will be considerably less than former estimates have made it.

Prof. E. C. Pickering estimates that the total number of stars visible on photographs down to the 16th magnitude (about the faintest visible in the great Lick telescope) will be about 50 millions.271 In the present writer’s enumeration, above referred to, many stars fainter than the 16th magnitude were included.

Admiral Smyth says, with reference to Sir William Herschel – perhaps the greatest observer that ever lived – “As to Sir William himself, he could unhesitatingly call every star down to the 6th magnitude, by its name, letter, or number.”272 This shows great powers of observation, and a wonderful memory.

On a photographic plate of the Pleiades taken with the Bruce telescope and an exposure of 6 hours, Prof. Bailey of Harvard has counted “3972 stars within an area 2° square, having Alcyone at its centre.”273 This would give a total of about 41 millions for the whole sky, if of the same richness.

With an exposure of 16 hours, Prof. H. C. Wilson finds on an area of less that 110′ square a total of 4621 stars. He thinks, “That all of these stars belong to the Pleiades group is not at all probable. The great majority of them probably lie at immense distances beyond the group, and simply appear in it by projection.”[274] He adds, “It has been found, however, by very careful measurements made during the last 75 years at the Königsbergh and Yale Observatories, that of the sixty-nine brighter stars, including those down to the 9th magnitude, only eight show any certain movement with reference to Alcyone. Since Alcyone has a proper motion or drift of 6″ per century, this means that all the brightest stars except the eight mentioned are drifting with Alcyone and so form a true cluster, at approximately the same distance from the earth. Six of the eight stars which show relative drift are moving in the opposite direction to the movement of Alcyone, and at nearly the same rate, so that their motion is only apparent. They are really stationary, while Alcyone and the rest of the cluster are moving past them.”274 This tends to show that the faint stars are really behind the cluster, and are unconnected with it.

It is a popular idea with some people that the Pole Star is the nearest of all the stars to the celestial pole. But photographs show that there are many faint stars nearer to the pole than the Pole Star. The Pole Star is at present at a distance of 1° 13′ from the real pole of the heavens, but it is slowly approaching it. The minimum distance will be reached in the year 2104. From photographs taken by M. Flammarion at the Juvisy Observatory, he finds that there are at least 128 stars nearer to the pole than the Pole Star! The nearest star to the pole was, in the year 1902, a small star of about 12½ magnitude, which was distant about 4 minutes of arc from the pole.275 The estimated magnitude shows that the Pole Star is nearly 10,000 times brighter than this faint star!

It has been found that Sirius is bright enough to cast a shadow under favourable conditions. On March 22, 1903, the distinguished French astronomer Touchet succeeded in photographing the shadow of a brooch cast by this brilliant star. The exposure was 1h 5m.

Martinus Hortensius seems to have been the first to see stars in daylight, perhaps early in the seventeenth century. He mentions the fact in a letter to Gassendi dated October 12, 1636, but does not give the date of his observation. Schickard saw Arcturus in broad daylight early in 1632. Morin saw the same bright star half an hour after sunset in March, 1635.

Some interesting observations were made by Professors Payne and H. C. Wilson, in the summer of 1904, at Midvale, Montana (U.S.A.), at a height of 4790 feet above sea-level. At this height they found the air very clear and transparent. “Many more stars were visible at a glance, and the familiar stars appeared more brilliant… In the great bright cloud of the Milky Way, between β and γ Cygni, one could count easily sixteen or seventeen stars, besides the bright ones η and χ,276 while at Northfield it is difficult to distinctly see eight or nine with the naked eye.” Some nebulæ and star fields were photographed with good results by the aid of a 2½-inch Darlot lens and 3 hours’ exposure.277

Prof. Barnard has taken some good stellar photographs with a lens of only 1½ inches in diameter, and 4 or 5 inches focus belonging to an ordinary “magic lantern”! He says that these “photographs with the small lens show us in the most striking manner how the most valuable and important information may be obtained with the simplest means.”278

With reference to the rising and setting of the stars due to the earth’s rotation on its axis, the late Sir George B. Airy, Astronomer Royal of England, once said to a schoolmaster, “I should like to know how far your pupils go into the first practical points for which reading is scarcely necessary. Do they know that the stars rise and set? Very few people in England know it. I once had a correspondence with a literary man of the highest rank on a point of Greek astronomy, and found that he did not know it!”279

Admiral Smyth says, “I have been struck with the beautiful blue tint of the smallest stars visible in my telescope. This, however, may be attributed to some optical peculiarity.” This bluish colour of small stars agrees with the conclusion arrived at by Prof. Pickering in recent years, that the majority of faint stars in the Milky Way have spectra of the Sirian type and, like that brilliant star, are of a bluish white colour. Sir William Herschel saw many stars of a redder tinge than other observers have noticed. Admiral Smyth says, “This may be owing to the effect of his metallic mirror or to some peculiarity of vision, or perhaps both.”280

The ancient astronomers do not mention any coloured stars except white and red. Among the latter they only speak of Arcturus, Aldebaran, Pollux, Antares, and Betelgeuse as of a striking red colour. To these Al-Sufi adds Alphard (α Hydræ).

Sir William Herschel remarked that no decidedly green or blue star “has ever been noticed unassociated with a companion brighter than itself.” An exception to Herschel’s rule seems to be found in the case of the star β Libræ, which Admiral Smyth called “pale emerald.” Mr. George Knott observed it on May 19, 1852, as “beautiful pale green” (3·7 inches achromatic, power 80), and on May 9, 1872, as “fine pale green” (5·5 inches achromatic, power 65).

The motion of stars in the line of sight, as shown by the spectroscope – should theoretically alter their brightness in the course of time; those approaching the earth becoming gradually brighter, while those receding should become fainter. But the distance of the stars is so enormous that even with very high velocities the change would not become perceptible for ages. Prof. Oudemans found that to change the brightness of a star by only one-tenth of a magnitude – a quantity barely perceptible to the eye-a number of years would be necessary, which is represented by the formula

5916 years

parallax × motion

for a star approaching the earth, and for a receding star

6195 years

p × m

This is in geographical miles, 1 geographical mile being equal to 4·61 English miles.

Reducing the above to English miles, and taking an average for both approaching and receding stars, we have

27,660 years

p × m

where p = parallax in seconds of arc, and m = radial velocity in English miles per second.

Prof. Oudemans found that the only star which could have changed in brightness by one-tenth of a magnitude since the time of Hipparchus is Aldebaran. This is taking its parallax as 0″·52. But assuming the more reliable parallax 0″·12 found by Dr. Elkin, this period is 4⅓ times longer. For Procyon, the period would be 5500 years.281 The above calculation shows how absurd it is to suppose that any star could have gained or lost in brightness by motion in the line of sight during historical times. The “secular variation” of stars is quite another thing. This is due to physical changes in the stars themselves.

The famous astronomer Halley, the second Astronomer Royal at Greenwich, says (Phil. Trans., 1796), “Supposing the number of 1st magnitude stars to be 13, at twice the distance from the sun there may be placed four times as many, or 52; which with the same allowance would nearly represent the star we find to be of the 2nd magnitude. So 9 × 13, or 117, for those at three times the distance; and at ten times the distance 100 × 13, or 1300 stars; of which distance may probably diminish the light of any of the stars of the 1st magnitude to that of the 6th, it being but the hundredth part of what, at their present distance, they appear with.” This agrees with the now generally accepted “light ratio” of 2·512 for each magnitude, which makes a first magnitude star 100 times the light of a 6th magnitude.

On the 4th of March, 1796,282 the famous French astronomer Lalande observed on the meridian a star of small 6th magnitude, the exact position of which he determined. On the 15th of the same month he again observed the star, and the places found for 1800 refer to numbers 16292-3 of the reduced catalogue. In the observation of March 4 he attached the curious remark, “Étoile singulière” (the observation of March 15 is without note). This remark of Lalande has puzzled observers who failed to find any peculiarity about the star. Indeed, “the remark is a strange one for the observer of so many thousands of stars to attach unless there was really something singular in the star’s aspect at the time.” On the evening of April 18, 1887, the star was examined by the present writer, and the following is the record in his observing book, “Lalande’s étoile singulière (16292-3) about half a magnitude less than η Cancri. With the binocular I see two streams of small stars branching out from it, north preceding like the tails of comet.” This may perhaps have something to do with Lalande’s curious remark.

The star numbered 1647 in Baily’s Flamsteed Catalogue is now known to have been an observation of the planet Uranus.283

Prof. Pickering states that the fainter stars photographed with the 8-inch telescope at Cambridge (U.S.A.) are invisible to the eye in the 15-inch telescope.284

Sir Norman Lockyer finds that the lines of sulphur are present in the spectrum of the bright star Rigel (β Orionis).285

About 8½° south of the bright star Regulus (α Leonis) is a faint nebula (H I, 4 Sextantis). On or near this spot the Capuchin monk De Rheita fancied he saw, in the year 1643, a group of stars representing the napkin of S. Veronica – “sudarium Veronicæ sive faciem Domini maxima similitudina in astris expressum.” And he gave a picture of the napkin and star group. But all subsequent observers have failed to find any trace of the star group referred to by De Rheita!286

The Bible story of the star of the Magi is also told in connection with the birth of the sun-gods Osiris, Horus, Mithra, Serapis, etc.287 The present writer has also heard it suggested that the phenomenon may have been an apparition of Halley’s comet! But as this famous comet is known to have appeared in the year B.C. 11, and as the date of the Nativity was probably not earlier than B.C. 5, the hypothesis seems for this (and other reasons) to be inadmissible. It has also been suggested that the phenomenon might have been an appearance of Tycho Brahé’s temporary star of 1572, known as the “Pilgrim star”; but there seems to be no real foundation for such an hypothesis. There is no reason to think that “temporary” or new stars ever appear a second time.