Part 20 (1/2)

VOLANS, the Flying Fish, is north of Mensa, and south and west of Argo.

Its brighter stars, with the exception of a and , form an irregular six-sided figure. Its brightest star is (365) according to the Harvard measures. The Cordoba estimates, however, range from 36 to 44, and Gould says its colour is ”bright yellow.” Williams rated it 38.

CHAMaeLION.--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 a (408 Harvard) and ? (410).

ARGO.--This large constellation extends much further south than Al-Sufi could follow it. The most southern star he mentions is e Carinae, but south of this are several bright stars. Carinae is 180 according to the Harvard measures; ? Carinae, 308; ?, 303; ?, 356; and others. A little north-west of ? is the long-period variable R Carinae (9{h} 29{m}7, S. 62 21', 1900). It varies from 45 at maximum to 10 at minimum, and the period is about 3097 days. A little east of R Carinae is another remarkable variable star, _l_ Carinae (R.A. 9{h} 42{m}5, S. 62 3'). It varies from 36 to 50 magnitude, with a period of 35 days from maximum to maximum. All the light changes can be observed with an opera-gla.s.s, 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 a (284 Harvard) and (326). These two stars form a fine pair south of a Crucis. Closely south-east of a is the short-period variable R Muscae. It varies from 65 to 76 magnitude, and its period is about 19 hours. All its changes of light may be observed with a good opera-gla.s.s.

APUS, the Bird of Paradise, lies south-east of Musca, and north of Octans.

Its brightest star is a, about the 4th magnitude. Williams calls it ”deep yellow.” About 3 north-west of a, in the direction of the Southern Cross, is ? Apodis, which was found to be variable at Cordoba from 5 to 6. 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, a, , ?, the brightest a being at the vertex. These three stars form with a Centauri an elongated cross. The stars and ? are about 3rd magnitude. is reddish. e (411, Harvard) is also reddish, and is nearly midway between and ?, and near the centre of the cross above referred to. a is a fine star (188 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 e is the short-period variable R Trianguli Australis (R.A. 15{h} 10{m}8, S. 66 8') discovered at Cordoba in 1871. It varies from 67 to 74, and the period is about 3{d} 7{h}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-gla.s.s. A little south-east of is another short-period variable, S Trianguli Australis (R.A. 15{h} 52{m}2, S. 63 30'), which varies from 64 to 74, with a period of 63 days; and all its fluctuations of light may also be observed with a good opera-gla.s.s.

CIRCINUS, the Compa.s.s, is a very small constellation lying between Triangulum and Centaurus. Its brightest star, a, is about 3 magnitude, about 4 south of a Centauri.

PAVO, the Peac.o.c.k, lies north of Octans and Apus, and south of Telescopium. Its brightest star is a, which is a fine bright star (212 Harvard). ? is a short-period variable. It varies from 38 to 52, 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-gla.s.s. e Pavonis was measured 410 at Harvard, but the Cordoba estimates vary from 36 to 42. 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, a, is probably referred to by Al-Sufi in his description of Sagittarius; it lies nearly midway between Sagittarii and a Gruis, and is the brightest star of the constellation.

The star e Indi (474 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 Phnix and Grus, east of Indus, and west of Hydrus. Its brightest star is a, 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--Erida.n.u.s.

5. The River of the G.o.d 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.[452] 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 (a Piscis Australis) is interesting as being the most southern 1st magnitude star visible in England, its meridian alt.i.tude at Greenwich being little more than eight degrees.[453]

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 a,”[454] 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_.