Astronomical Curiosities Part 19

"Dixit et antiqui monumenta perennia facti Anguis, Avis, Crater sidera, juncta mic.u.n.t."

The star a Crateris was rated 4th magnitude by Al-Sufi and all other observers, and the Harvard measures make it 420, a satisfactory agreement. It has three companions noted by Admiral Smyth. One of these he called "intense blood colour." This is R Crateris, now known to be variable from above the 8th magnitude to below the 9th. Sir John Herschel called it an "intense scarlet star, a curious colour." With 3-inch refractor in the Punjab I found it "full scarlet." It is one of an open pair, the further of the two from a. There is a third star about 9th magnitude a little south of it. Ward saw a 13th magnitude star between a and R with a 2?-inch (Wray) refractor. This I saw "readily" with my 3-inch. Smyth does not mention this faint star, although he used a much larger telescope.

Corvus, the Crow, is a small constellation, north of Hydra. Aratus says "the Crow form seems to peck the fold of the water snake" (Hydra). The victory which Valerius Corvinus is said to have owed to a crow has given it the name of Pomptina, because the victory took place near the Pontine marshes.[446] A quadrilateral figure is formed by its four brightest stars, ?, d, , and e Corvi. This figure has sometimes been mistaken for the Southern Cross by those who are not familiar with the heavens. But the stars of the Southern Cross are much brighter.

The constellation Centaurus, the Centaur, lies south of Hydra and Libra, and north of the Southern Cross. According to Dupuis, Centaurus represents the 3rd "labour of Hercules," his triumph over the Centaurs.[447] The Centaurs were supposed to be a people living in the vicinity of Mount Ossa, who first rode on horses. The constellation was also called Semivir, Chiron, Phobos, Minotaurus, etc. Al-Sufi says it "is represented by the figure of an animal, of which the forepart is the upper part of a man from the head to end of the back, and its hinder part is the hinder part of a horse, from the beginning of the back to the tail. It is to the south of the Balance [Libra] turning its face towards the east, and the hinder part of the beast towards the west."

Al-Sufi describes very clearly the four bright stars of the famous "Southern Cross." Owing to precession these stars were some 7 further north in the tenth century than they are at present, and they could have been all seen by Al-Sufi, when on the meridian. In the time of Ptolemy and Hipparchus, they were still further north, and about 5000 years ago they were visible in the lat.i.tude of London. Dante speaks of these four stars as emblematical of the four cardinal virtues, Justice, Temperance, Fort.i.tude, and Prudence.

Closely south-east of a and Crucis is the dark spot in the Milky Way known as the "Coal Sack," which forms such a conspicuous object near the Southern Cross. It was first described by Pinzon in 1499; and afterwards by Lacaille in 1755. Although to the naked eye apparently black, photographs show that it contains many faint stars, but, of course, much less numerous than in the surrounding regions. The dark effect is chiefly caused by contrast with the brilliancy of the Milky Way surrounding it.

Al-Sufi also mentions the bright stars a and Centauri which follow the Southern Cross. He says that the distance between them "is four cubits,"

that is about 9 20', but it is less than this now. a has a large "proper motion" of 3"67 per annum, and was farther from in Al-Sufi's time than it is at present. This, however, would not _wholly_ account for the difference, and Al-Sufi's over-estimate is probably due to the well-known effect by which the distance between two stars is _apparently_ increased when they are near the horizon. Several of Al-Sufi's distances between southern stars are over-estimated, probably for the same reason.

The constellation Lupus, the Wolf, is south of Libra and Scorpio. It lies along the western border of the Milky Way. According to ancient writers it represents Lycaon, King of Arcadia, a contemporary of Cecrops, who is said to have sacrificed human victims, and on account of his cruelty was changed into a wolf. Another fable is that it represents a wolf sacrificed by the Centaur Chiron. According to Brown, Lupus appears on the Euphratian planisphere discovered by George Smyth in the palace of Sennacherib. Al-Sufi called it _al-sabu_, "the Wild Beast." It was also called _al-fand_, "the Leopard," and _al-asada_, "the Lioness."

Ara, the Altar, lies south of Scorpio. According to ancient writers it represents an altar built by Vulcan, when the G.o.ds made war against the t.i.tans. It is called by Al-Sufi _al-midjman_, "the Scent Box," or "the Altar."

The little constellation Corona Australis, the Southern Crown, lies south and west of Sagittarius, east of Scorpio, and west of Telescopium. Aratus refers to the stars in Corona Australis as--

"Other few Before the Archer under his forefeet Led round in circle roll without a name."[449]

But the constellation was known by the names Caduceus, Orbiculus, Corona Sagittarii, etc. The ancient poets relate that Bacchus placed this crown in the sky in honour of his mother Semele.[450] Others say that it represents the crown conferred on Corinne of Thebes, famous as a poet.

The small constellation Piscis Australis, or the Southern Fish, lies south of Capricornus and Aquarius. In the most ancient maps it is represented as a fish drinking the water which flows from the urn of Aquarius.

A good many constellations have been added to the heavens since the days of Al-Sufi, and notes on some of these may be of interest.

CAMELOPARDALIS.--This constellation first appears on a celestial planisphere published by Bartschius in the year 1624. It was not formed by Bartschius himself, but by the navigators of the sixteenth century. It lies south of Ursa Minor, north of Perseus and Auriga, east of Draco, and west of Ca.s.siopeia. It contains no star brighter than the 4th magnitude.

LYNX.--This constellation is south of Camelopardalis and Ursa Major, and north of Gemini and Cancer. It was formed by Hevelius in 1660, and he called it the Lynx, because, he said, it contained only faint stars and "it was necessary to have the eyes of a lynx" to see them! Some of them were, however, observed by Ptolemy and Al-Sufi, and are mentioned by the latter under Ursa Major.

CANES VENATICI, or the Hunting Dogs.--This was formed by Hevelius in 1660.

It lies south of the Great Bear's tail, north of Coma Berenices, east of Ursa Major, and west of Bootis. Its brightest stars a (12) and (8) were observed by Al-Sufi, and included by him in the "extern" stars of Ursa Major.

COMA BERENICES.--This constellation lies between Canes Venatici and Virgo.

Although it was not included among the old forty-eight constellations of Ptolemy, it is referred to by Al-Sufi as the Plat, or Tress of Hair, and he included its stars Flamsteed 12, 15, and 21 in the "extern" stars of Leo. It was originally formed by the poet Callimachus in the third century B.C., but was not generally accepted until reformed by Hevelius.

Callimachus lived at Alexandria in the reigns of Ptolemy Philadelphus and Ptolemy Euergetes, and was chief librarian of the famous library of Alexandria from about B.C. 260 until his death in B.C. 240. Eratosthenes was one of his pupils. The history of the constellation is as follows: Berenice, wife of Ptolemy Euergetes, made a vow, when her husband was leaving her on a military expedition, that if he returned in safety she would cut off her hair and consecrate it in the temple of Mars. Her husband returned, and she fulfilled her vow. But on the next day the hair had disappeared--stolen from the temple--and Conon the mathematician showed Ptolemy seven stars near the constellation of the Lion which did not belong to any constellation. These were formed into a constellation and called Berenice's Hair. Conon is referred to by Catullus in the lines--

"Idem me ille Conon cleste numine vidit E. Berenico vertice Caesariem."

Coma Berenices first occurs as a distinct constellation in the catalogue contained in the Rudolphine Tables formed by Kepler (epoch 1600) from the observations of Tycho Brahe.[451] Bayer subst.i.tuted a sheaf of corn, an idea derived from an ancient ma.n.u.script.

LEO MINOR.--This small constellation lies between Ursa Major and Leo, and east of the Lynx. It was formed by Halley about the year 1660; but is referred to by Al-Sufi, who includes one of its stars (Fl. 41) in the "extern" stars of Leo. There are, however, several brighter stars in the group. The brightest, Fl. 46, was measured 392 at Harvard. The star Fl.

37 was called _praecipua_ (or brightest) by Tycho Brahe, and rated 3, but as it was measured only 477 at Harvard it may possibly have diminished in brightness.

s.e.xTANS.--This constellation lies south of Leo, and north and east of Hydra. It was formed by Hevelius about the year 1680. According to the Harvard photometric measures its brightest star is Fl. 15 (450).

MONOCEROS, or the Unicorn, lies south of Gemini and Canis Minor, north of Canis Major and Argo, east of Orion, and west of Hydra. It appears on the planisphere of Bartschius, published in 1624. According to Scaliger it is shown on an old Persian sphere. One of its stars, Fl. 22, is mentioned by Al-Sufi among the "extern" stars of Canis Major (No. 1). Another, Fl. 30, is given under Hydra ("Extern" No. 1) and Fl. 8, 13, and 15 are apparently referred to in Gemini. The star 15 Monocerotis is a little south of ?

Geminorum, and was measured 459 magnitude at Harvard. It was at one time supposed to be variable with a short period (about 3 days), but this variation has not been confirmed. The spectrum is of the fifth type--with bright lines--a very rare type among naked-eye stars. It is a triple star (5, 88, 112: 2"9, 16"3) and should be seen with a 4-inch telescope. It has several other small companions, one of which (1392: 75"7) has been suspected of variation in light. It was estimated 8 by Main in 1863, but only 12 by Sadler in 1875. Observing it on March 28, 1889, with 3-inch refractor, I found it about one magnitude brighter than a star closely preceding, and estimated it 8 or 8 magnitude. It is probably variable and should be watched.

SCUTUM SOBIESKI.--This is, or was, a small constellation in the southern portion of Aquila, which was formed by Hevelius in 1660 in honour of the Polish hero Sobieski. Its princ.i.p.al stars, which lie south-west of ?

Aquilae, were mentioned by Al-Sufi and are referred to by him under that constellation. It contains a very bright spot of Milky Way light, which may be well seen in the month of July just below the star ? Aquilae.

Closely south of the star 6 Aquilae is a remarkable variable star R Scuti (R.A. 18{h} 42{m}2, S. 5 49'). It varies from 48 to 78 with an irregular period. All the light changes can be observed with a good opera-gla.s.s.

VULPECULA, the Fox.--This modern constellation lies south of Cygnus, north of Sagitta and Delphinus, east of Hercules, and west of Pegasus. It was formed by Hevelius in 1660. One of its stars, 6 Vulpeculae, is mentioned by Al-Sufi in describing the constellation Cygnus. Closely north-west of 32 Vulpeculae is the short-period variable T Vulpeculae. It varies from 55 to 62 magnitude, and its period is 4436 days. This is an interesting object, and all the changes of light can be observed with an opera-gla.s.s.

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 (a Lacertae) is about the 4th magnitude. About one degree south-west of 7 is 5 Lacertae, 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 Phnix. Some of its stars are referred to by Al-Sufi under Erida.n.u.s as lying within the large triangle formed by Ceti, Fomalhaut, and a Phnicis. The brightest star is a, about 12 south of Ceti (439 magnitude Harvard). About 7 south-east of a is the red and variable star R Sculptoris; variable from 62 to 88 magnitude, with a period of about 376 days. Gould describes it as "intense scarlet." It has a spectrum of the fourth type.

PHNIX.--This constellation lies south of Sculptor. Some of its stars are referred to by Al-Sufi, under Erida.n.u.s, as forming a boat-shaped figure.

These are evidently a, ?, , , ?, and ?. a 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 Erida.n.u.s, and east of Sculptor and Phnix. It was formed by Lacaille, and is supposed to represent a chemical furnace with an alembic and receiver! Its brightest star, a Fornacis, is identical with 12 Eridani.

CaeLUM, the Sculptor's Tools, is a small constellation east of Columba, and west of Erida.n.u.s. It was formed by Lacaille. The brightest stars are a and ?, which are about 4 magnitude. a has a faint companion; and ? 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, a, 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 a, d, and ?, 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 4 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 s Octantis, which is within one degree of the pole. It was estimated 58 at Cordoba. The brightest star in the constellation is ?

Octantis (a, Proctor), which lies about 12 degrees from the pole in the direction of Indus and Microscopium. The Harvard measure is 374 magnitude.

HYDRUS, the Water-Snake, is north of Octans in the direction of Achernar (a Eridani). The brightest star is , which lies close to ? Octantis. The Harvard measure is 290. 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. ? Hydri is a comparatively bright star of about the 3rd magnitude, about 15 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 Erida.n.u.s. Three of its stars, a, d, and ?, at the extreme northern end of the constellation, seem to be referred to by Al-Sufi in his description of Erida.n.u.s, 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 a (336 Harvard, 33 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 a (347 Harvard) and (381 Harvard, but suspected of variation). About 3 east of a Reticuli is the variable star R Doradus. It varies from 48 to 68, 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-gla.s.s.

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 a (330 Harvard).