Part 19 (2/2)
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).
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