Astronomical Curiosities: Facts and Fallacies

Lacerta. – This little constellation lies south of Cepheus and north of Pegasus. Its formation was first suggested by Roger and Anthelm in 1679, and it was called by them “The Sceptre and the Hand of Justice.” It was named Lacerta by Hevelius in 1690, and this name it still retains. Al-Sufi seems to refer to its stars in his description of Andromeda, but does not mention any star in particular. It brightest star Fl. 7 (α Lacertæ) is about the 4th magnitude. About one degree south-west of 7 is 5 Lacertæ, a deep orange star with a blue companion in a fine field.

There are some constellations south of the Equator which, although above Al-Sufi’s horizon when on the meridian, are not described by him, as they were formed since his time. These are as follows: —

Sculptor. – This constellation lies south of Aquarius and Cetus, and north of Phœnix. Some of its stars are referred to by Al-Sufi under Eridanus as lying within the large triangle formed by β Ceti, Fomalhaut, and α Phœnicis. The brightest star is α, about 12° south of β Ceti (4·39 magnitude Harvard). About 7° south-east of α is the red and variable star R Sculptoris; variable from 6·2 to 8·8 magnitude, with a period of about 376 days. Gould describes it as “intense scarlet.” It has a spectrum of the fourth type.

Phœnix. – This constellation lies south of Sculptor. Some of its stars are referred to by Al-Sufi, under Eridanus, as forming a boat-shaped figure. These are evidently α, κ, μ, β, ν, and γ. α is at the south-eastern angle of Al-Sufi’s triangle referred to above (under “Sculptor”). (See Proctor’s Atlas, No. 3.)

Fornax, the Furnace, lies south of Cetus, west of Eridanus, and east of Sculptor and Phœnix. It was formed by Lacaille, and is supposed to represent a chemical furnace with an alembic and receiver! Its brightest star, α Fornacis, is identical with 12 Eridani.

Cælum, the Sculptor’s Tools, is a small constellation east of Columba, and west of Eridanus. It was formed by Lacaille. The brightest stars are α and γ, which are about 4½ magnitude. α has a faint companion; and γ is a wide double star to the naked eye.

Antlia, the Air Pump, lies south of Hydra, east and north of Argo, and west of Centaurus. It was formed by Lacaille. It contains no star brighter than 4th magnitude. The brightest, α, has been variously rated from 4 to 5, and Stanley Williams thinks its variability “highly probable.”

Norma, the Rule, lies south of Scorpio. It contains no star brighter than the 4th magnitude.

Telescopium. – This modern constellation lies south of Corona Australis, and north of Pavo. Its stars α, δ, and ζ, which lie near the northern boundary of the constellation, are referred to by Al-Sufi in his description of Ara.

Microscopium. – This small constellation is south of Capricornus, and west of Piscis Australis. Its stars seem to be referred to by Al-Sufi as having been seen by Ptolemy, but he does not specify their exact positions. It contains no star brighter than 4½ magnitude.

South of Al-Sufi’s horizon are a number of constellations surrounding the south pole, which, of course, he could not see. Most of these have been formed since his time, and these will now be considered; beginning with that immediately surrounding the South Pole (Octans), and then following the others as nearly as possible in order of Right Ascension.

Octans. – This is the constellation surrounding the South Pole of the heavens. There is no bright star near the Pole, the nearest visible to the naked eye being σ Octantis, which is within one degree of the pole. It was estimated 5·8 at Cordoba. The brightest star in the constellation is ν Octantis (α, Proctor), which lies about 12 degrees from the pole in the direction of Indus and Microscopium. The Harvard measure is 3·74 magnitude.

Hydrus, the Water-Snake, is north of Octans in the direction of Achernar (α Eridani). The brightest star is β, which lies close to θ Octantis. The Harvard measure is 2·90. Gould says its colour is “clear yellow.” It has a large proper motion of 2″·28 per annum. Sir David Gill found a parallax of 0″·134, and this combined with the proper motion gives a velocity of 50 miles a second at right angles to the line of sight. γ Hydri is a comparatively bright star of about the 3rd magnitude, about 15½ degrees from the South Pole. It is reddish, with a spectrum of the third type.

Horologium, the Clock, is north of Hydra, and south of Eridanus. Three of its stars, α, δ, and ψ, at the extreme northern end of the constellation, seem to be referred to by Al-Sufi in his description of Eridanus, but he does not give their exact positions. Most of the stars forming this constellation were below Al-Sufi’s horizon.

Reticulum, the Net, is a small constellation to the east of Hydrus and Horologium. The brightest star of the constellation is α (3·36 Harvard, 3·3 Cordoba, and “coloured”).

Dorado, the Sword Fish, lies east of Reticulum and west of Pictor. It contains only two stars brighter than the 4th magnitude. These are α (3·47 Harvard) and β (3·81 Harvard, but suspected of variation). About 3° east of α Reticuli is the variable star R Doradus. It varies from 4·8 to 6·8, and its period is about 345 days. Gould calls it “excessively red.” It may be followed through all its fluctuations of light with an opera-glass.

Mensa, or Mons Mensa, the Table Mountain, lies between Dorado and the South Pole, and represents the Table Mountain of the Cape of Good Hope. It contains no star brighter than the 5th magnitude.

Pictor, the Painter’s Easel, lies north of Doradus, and south of Columba. It contains no very bright stars, the brightest being α (3·30 Harvard).

Volans, the Flying Fish, is north of Mensa, and south and west of Argo. Its brighter stars, with the exception of α and β, form an irregular six-sided figure. Its brightest star is β (3·65) according to the Harvard measures. The Cordoba estimates, however, range from 3·6 to 4·4, and Gould says its colour is “bright yellow.” Williams rated it 3·8.

Chamælion. – This small constellation lies south of Volans, and north of Mensa and Octans. None of its stars are brighter than the 4th magnitude, its brightest being α (4·08 Harvard) and γ (4·10).

Argo. – This large constellation extends much further south than Al-Sufi could follow it. The most southern star he mentions is ε Carinæ, but south of this are several bright stars. β Carinæ is 1·80 according to the Harvard measures; υ Carinæ, 3·08; θ, 3·03; ω, 3·56; and others. A little north-west of ι is the long-period variable R Carinæ (9h 29m·7, S. 62° 21′, 1900). It varies from 4·5 at maximum to 10 at minimum, and the period is about 309·7 days. A little east of R Carinæ is another remarkable variable star, l Carinæ (R.A. 9h 42m·5, S. 62° 3′). It varies from 3·6 to 5·0 magnitude, with a period of 35½ days from maximum to maximum. All the light changes can be observed with an opera-glass, or even with the naked eye. It was discovered at Cordoba. The spectrum is of the solar type (G).

Musca, the Bee, is a small constellation south of the Southern Cross and Centaurus. Its brightest stars are α (2·84 Harvard) and β (3·26). These two stars form a fine pair south of α Crucis. Closely south-east of α is the short-period variable R Muscæ. It varies from 6·5 to 7·6 magnitude, and its period is about 19 hours. All its changes of light may be observed with a good opera-glass.

Apus, the Bird of Paradise, lies south-east of Musca, and north of Octans. Its brightest star is α, about the 4th magnitude. Williams calls it “deep yellow.” About 3° north-west of α, in the direction of the Southern Cross, is θ Apodis, which was found to be variable at Cordoba from 5½ to 6½. The spectrum is of the third type, which includes so many variable stars.

Triangulum Australis, the Southern Triangle, is a small constellation north of Apus, and south of Norma. A fine triangle, nearly isosceles, is formed by its three bright stars, α, β, γ, the brightest α being at the vertex. These three stars form with α Centauri an elongated cross. The stars β and γ are about 3rd magnitude. β is reddish. ε (4·11, Harvard) is also reddish, and is nearly midway between β and γ, and near the centre of the cross above referred to. α is a fine star (1·88 Harvard) and is one of the brightest stars in the sky – No. 33 in a list of 1500 highest stars given by Pickering. About 1° 40′ west of ε is the short-period variable R Trianguli Australis (R.A. 15h 10m·8, S. 66° 8′) discovered at Cordoba in 1871. It varies from 6·7 to 7·4, and the period is about 3d 7h·2. Although not visible to ordinary eyesight it is given here, as it is an interesting object and all its light changes may be well seen with an opera-glass. A little south-east of β is another short-period variable, S Trianguli Australis (R.A. 15h 52m·2, S. 63° 30′), which varies from 6·4 to 7·4, with a period of 6·3 days; and all its fluctuations of light may also be observed with a good opera-glass.

Circinus, the Compass, is a very small constellation lying between Triangulum and Centaurus. Its brightest star, α, is about 3½ magnitude, about 4° south of α Centauri.

Pavo, the Peacock, lies north of Octans and Apus, and south of Telescopium. Its brightest star is α, which is a fine bright star (2·12 Harvard). κ is a short-period variable. It varies from 3·8 to 5·2, and the period is about 9 days. This is an interesting object, as all the fluctations of light can be observed by the naked eye or an opera-glass. ε Pavonis was measured 4·10 at Harvard, but the Cordoba estimates vary from 3·6 to 4·2. Gould says “it is of a remarkably blue colour.”

Indus. – This constellation lies north of Octans, and south of Sagittarius, Microscopium, and Grus. One of its stars, α, is probably referred to by Al-Sufi in his description of Sagittarius; it lies nearly midway between β Sagittarii and α Gruis, and is the brightest star of the constellation. The star ε Indi (4·74 Harvard) has a remarkably large proper motion of 4″·68 per annum. Its parallax is about 0″·28, and the proper motion indicates a velocity of about 49 miles a second at right angles to the line of sight.

Toucan. – This constellation lies north of Octans, and south of Phœnix and Grus, east of Indus, and west of Hydrus. Its brightest star is α, of about the 3rd magnitude.

There are seven “celestial rivers” alluded to by the ancient astronomers: —

1. The Fish River, which flows from the urn of Aquarius.

2. The “River of the Bird,” or the Milky Way in Cygnus.

3. The River of the Birds – 2, including Aquila.

4. The River of Orion – Eridanus.

5. The River of the god Marduk – perhaps the Milky Way in Perseus.

6. The River of Serpents (Serpens, or Hydra).

7. The River of Gan-gal (The High Cloud) – probably the Milky Way as a whole.

There are four serpents represented among the constellations. These are Hydra, Hydrus, Serpens, and Draco.

According to the late Mr. Proctor the date of the building of the Great Pyramid was about 3400 B.C.450 At this time the Spring Equinox was in Taurus, and this is referred to by Virgil. But this was not so in Virgil’s time, when – on account of the precession of the equinoxes – the equinoctial point had already entered Pisces, in which constellation it still remains. At the date 3400 B.C. the celestial equator ran along the whole length of the constellation Hydra, nearly through Procyon, and a little north of the bright red star Antares.

The star Fomalhaut (α Piscis Australis) is interesting as being the most southern 1st magnitude star visible in England, its meridian altitude at Greenwich being little more than eight degrees.451

With reference to the Greek letters given to the brighter stars by Bayer (in his Atlas published in 1603), and now generally used by astronomers, Mr. Lynn has shown that although “Bayer did uniformly designate the brightest stars in each constellation by the letter α,”452 it is a mistake to suppose – as has often been stated in popular books on astronomy – that he added the other Greek letters in order of brightness. That this is an error clearly appears from Bayer’s own “Explicatio” to his Atlas, and was long since pointed out by Argelander (1832), and by Dr. Gould in his Uranometria Argentina. Gould says, “For the stars of each order, the sequence of the letters in no manner represents that of their brightness, but depended upon the positions of the stars in the figure, beginning usually at the head, and following its course until all the stars of that order of magnitude were exhausted.” Mr. Lynn says, “Perhaps one of the most remarkable instances in which the lettering is seen at a glance not to follow the order of the letters is that of the three brightest stars in Aquila [Al-Sufi’s ‘three famous stars’], γ being evidently brighter than β. But there is no occasion to conjecture from this that any change of relative brightness has taken place. Bayer reckoned both of these two of the third magnitude, and appears to have arranged β before γ, according to his usual custom, simply because β is in the neck of the supposed eagle, and γ at the root of one of the wings.”453 Another good example is found in the stars of the “Plough,” in which the stars are evidently arranged in the order of the figure and not in the order of relative brightness. In fact, Bayer is no guide at all with reference to star magnitudes. How different Al-Sufi was in this respect!

The stars Aldebaran, Regulus, Antares, and Fomalhaut were called royal stars by the ancients. The reason of this was that they lie roughly about 90° apart, that is 6 hours of Right Ascension. So, if through the north and south poles of the heavens and each of these stars we draw great circles of the sphere, these circles will divide the sphere into four nearly equal parts, and the ancients supposed that each of these stars ruled over a quarter of the sphere, an idea probably connected with astrology. As the position of Aldebaran is R.A. 4h 30m, Declination North 16° 19′, and that of Antares is R.A. 16h 15m, Declination South 25° 2′, these two stars lie at nearly opposite points of the celestial sphere. From this it follows that our sun seen from Aldebaran would lie not very far from Antares, and seen from Antares it would appear not far from Aldebaran.

The following may be considered as representative stars of different magnitudes. For those of first magnitude and fainter I have only given those for which all the best observers in ancient and modern times agree, and which have been confirmed by modern photometric measures. The Harvard measures are given: —

CHAPTER XX

The Visible Universe

Some researches on the distribution of stars in the sky have recently been made at the Harvard Observatory (U.S.A.). The principal results are: – (1) The number of stars on any “given area of the Milky Way is about twice as great as in an equal area of any other region.” (2) This ratio does not increase for faint stars down to the 12th magnitude. (3) “The Milky Way covers about one-third of the sky and contains about half of the stars.” (4) There are about 10,000 stars of magnitude 6·6 or brighter, 100,000 down to magnitude 8·7, one million to magnitude 11, and two millions to magnitude 11·9. It is estimated that there are about 18 millions of stars down to the 15th magnitude visible in a telescope of 15 inches aperture.454

According to Prof. Kapteyn’s researches on stellar distribution, he finds that going out from the earth into space, the “star density” – that is, the number of stars per unit volume of space – is fairly constant until we reach a distance of about 200 “light years.” From this point the density gradually diminishes out to a distance of 2500 “light years,” at which distance it is reduced to about one-fifth of the density in the sun’s vicinity.455

In a letter to the late Mr. Proctor (Knowledge, November, 1885, p. 21), Sir John Herschel suggested that our Galaxy (or stellar system) “contained within itself miniatures of itself.” This beautiful idea is probably true. In his account of the greater “Magellanic cloud,” Sir John Herschel describes one of the numerous objects it contains as follows: —

“Very bright, very large; oval; very gradually pretty, much brighter in the middle; a beautiful nebula; it has very much the resemblance to the Nubecula Major itself as seen with the naked eye, but it is far brighter and more impressive in its general aspect as if it were doubled in intensity. Note – July 29, 1837. I well remember this observation, it was the result of repeated comparisons between the object seen in the telescope and the actual nubecula as seen high in the sky on the meridian, and no vague estimate carelessly set down. And who can say whether in this object, magnified and analysed by telescopes infinitely superior to what we now possess, there may not exist all the complexity of detail that the nubecula itself presents to our examination?”456

The late Lord Kelvin, in a remarkable address delivered before the Physical Science Section of the British Association at its meeting at Glasgow in 1901, considered the probable quantity of matter contained in our Visible Universe. He takes a sphere of radius represented by the distance of a star having a parallax of one-thousandth of a second (or about 3000 years’ journey for light), and he supposes that uniformly distributed within this sphere there exists a mass of matter equal to 1000 million times the sun’s mass. With these data he finds that a body placed originally at the surface of the sphere would in 5 million years acquire by gravitational force a velocity of about 12½ miles a second, and after 25 million of years a velocity of about 67 miles a second. As these velocities are of the same order as the observed velocities among the stars, Lord Kelvin concludes that there is probably as much matter in our universe as would be represented by a thousand million suns. If we assumed a mass of ten thousand suns the velocities would be much too high. The most probable estimate of the total number of the visible stars is about 100 millions; so that if Lord Kelvin’s calculations are correct we seem bound to assume that space contains a number of dark bodies. The nebulæ, however, probably contain vast masses of matter, and this may perhaps account – partially, at least – for the large amount of matter estimated by Lord Kelvin. (See Chapter on “Nebulæ.”)

In some notes on photographs of the Milky Way, Prof. Barnard says with reference to the great nebula near ρ Ophiuchi, “The peculiarity of this region has suggested to me the idea that the apparently small stars forming the ground work of the Milky Way here, are really very small bodies compared with our own sun”; and again, referring to the region near β Cygni, “One is specially struck with the apparent extreme smallness of the general mass of the stars in this region.” Again, with reference to χ Cygni, he says, “The stars here also are remarkably uniform in size.”457

Eastman’s results for parallax seem to show that “the fainter rather than the brighter stars are nearest to our system.” But this apparent paradox is considered by Mr. Monck to be very misleading;458 and the present writer holds the same opinion.

Prof. Kapteyn finds “that stars whose proper motions exceed 0″·05 are not more numerous in the Milky Way than in other parts of the sky; or, in other words, if only the stars having proper motions of 0″·05 or upwards were mapped, there would be no aggregation of stars showing the existence of the Milky Way.”459

With reference to the number of stars visible on photographs, the late Dr. Isaac Roberts says —

“So far as I am able at present to judge, under the atmospheric conditions prevalent in this country, the limit of the photographic method of delineation will be reached at stellar, or nebular, light of the feebleness of about 18th-magnitude stars. The reason for this inference is that the general illumination of the atmosphere by starlight concentrated upon a film by the instrument will mask the light of objects that are fainter than about 18th-magnitude stars.”460

With reference to blank spaces in the sky, the late Mr. Norman Pogson remarked —

“Near S Ophiuchi we find one of the most remarkable vacuities in this hemisphere – an elliptic space of about 65′ in length in the direction of R.A., and 40′ in width, in which there exists no star larger than the 13th magnitude … it is impossible to turn a large telescope in that direction and, if I may so express it, view such black darkness, without a feeling that we are here searching into the remote regions of space, far beyond the limits of our own sidereal system.”461

Prof. Barnard describes some regions in the constellation Taurus containing “dark lanes” in a groundwork of faint nebulosity. He gives two beautiful photographs of the regions referred to, and says that the dark holes and lanes are apparently darker than the sky in the immediate vicinity. He says, “A very singular feature in this connection is that the stars also are absent in general from the lanes.” A close examination of these photographs has given the present writer the impression that the dark lanes and spots are in the nebulosity, and that the nebulosity is mixed up with the stars. This would account for the fact that the stars are in general absent from the dark lanes. For if there is an intimate relation between the stars and the nebulosity, it would follow that where there is no nebulosity in this particular region there would be no stars. Prof. Barnard adds that the nebulosity is easily visible in a 12-inch telescope.462

With reference to the life of the universe, Prof. F. R. Moulton well says —

“The lifetime of a man seems fairly long, and the epoch when Troy was besieged, or when the Pharaohs piled up the pyramids in the valley of the Nile, or when our ancestors separated on the high plateaux of Asia, seems extremely remote, but these intervals are only moments compared to the immense periods required for geological evolutions and the enormously greater ones consumed in the developement of worlds from widely extended nebulous masses. We recognize the existence of only those forces whose immediate consequences are appreciable, and it may be that those whose effects are yet unseen are really of the highest importance. A little creature whose life extended over only two or three hours of a summer’s day might be led, if he were sufficiently endowed with intelligence, to infer that passing clouds were the chief influence at work in changing the climate instead of perceiving that the sun’s slow motion across the sky would bring on the night and its southward motion the winter.”463

In a review of my book Astronomical Essays in The Observatory, September, 1907, the following words occur. They seem to form a good and sufficient answer to people who ask, What is there beyond our visible universe? “If the stellar universe is contained in a sphere of say 1000 stellar units radius, what is there beyond? To this the astronomer will reply that theories and hypotheses are put forward for the purpose of explaining observed facts; when there are no facts to be explained, no theory is required. As there are no observed facts as to what exists beyond the farthest stars, the mind of the astronomer is a complete blank on the subject. Popular imagination can fill up the blank as it pleases.” With these remarks I fully concur.

In his address to the British Association, Prof. G. H. Darwin (now Sir George Darwin) said —

“Man is but a microscopic being relatively to astronomical space, and he lives on a puny planet circling round a star of inferior rank. Does it not, then, seem futile to imagine that he can discover the origin and tendency of the Universe as to expect a housefly to instruct us as to the theory of the motions of the planets? And yet, so long as he shall last, he will pursue his search, and will no doubt discover many wonderful things which are still hidden. We may indeed be amazed at all that man has been able to find out, but the immeasurable magnitude of the undiscovered will throughout all time remain to humble his pride. Our children’s children will still be gazing and marvelling at the starry heavens, but the riddle will never be read.”

The ancient philosopher Lucretius said —

“Globed from the atoms falling slow or swiftI see the suns, I see the systems liftTheir forms; and even the system and the sunsShall go back slowly to the eternal drift.”464

But it has been well said that the structure of the universe “has a fascination of its own for most readers quite apart from any real progress which may be made towards its solution.”465