ASTRONOMICAL NOTES FOR OCTOBER.

Press, Volume LXVII, Issue 14162, 30 September 1911, Page 8

ASTRONOMICAL NOTES FOR OCTOBER.

(BT THE REV. P. W. FAIECLOtTGH, F.R.A.S.) The sun has now crossed the equator into the Southern Hemisphere. More than half of twenty-four hours aro now sun-lit, and the day is increasing in length at maximum speed. The point at which the sun crosses the equator is not fixed. It advanoes a little every year, so that, in a great cyclo of 26,000 years, the crossing point makee a complete circuit of the equator. This is owing to the earth's rocking motion, like that of a top that is about to fall. The rocking is caused by. the attractions of the sun and the moon on the equatorial bilge of the earth. The great ' top swings round in 26,000 yoars causing the polo to describe a wide circle on the heavens. This movement is called the Procession of the Equinoxes, meaning the forward movement of the points at which tho sun crosses tho line in March and September. It is doubted whether there are any such things as 'equinoxial gales.' That is. it is doubted whether there is any efficient cause for gales at the equinoxes more than at other. times, which would justify the use of the term. Venus, having passed from the eastern to tho western side of the sun, is now vifiib'le in tho morning shortly before sunriee. Meroury Jβ also a morning star. Saturn rises late in the evening, and Mare a little later. Saturn is above the Pleiades, and Mars bolow Aldebaran. Jupiter is still with us. as an evening etar in the west. The next three months will be favourable for the observation of Mars. An. annular, or ring eolipse of tb« sun, occurs on the 22nd of this month. The central lino begins near the Caspian and sweeps by Formosa and south of New Guinea. In Wellington it will bo visible, to careful observers, for 13 minutes but will cover only one hundredth part of the eun's diameter. About 25 miles further sooth it wiil be missed altogether. Tho humidity of the atmosphere at Vavau interfered with the success oi photographs, because the temperature fell suddenly during totality, and den condensed on glass. Astronomers arc expecting better things nert year, when an eclipse will bo seen over Brazil. Counting back three same periods of 18 years 10 days and £ hours, we find that this eclipse was seen in Britain in 1858, the last total colipso seen there; Halley's Oomefc has been observed foi 21 months —easily a record—and is now beyond the orbit of Jupiter. His voyage is about . 0,000>000,000 miles ir length, and he has used up all his beet speed in doing about 500,000,00( mile*. The new comet discovered on Julj 6th, and afterwards seen at Pertl (W.A.), passed its perihelion on June 20th, and, in August, passed withir 85,000,000 miles of the earth. It wa< leintly visible to a good eye. Its patt eeems very similar to that of the cornel of 1790. I'hat, however, would npi prove identity, for the coniete Of 1800, 1843, 1882, and 1887 were all pursuing tho same path, and probably had i common origin. Wolf's periodic comet which belongs to Jupiter's family, wai rediscovered within six seconds of ar< of the predicted place. That is withir about a eoOth, part of the appsfceni diameter of the moon—which is t record. This comet will reach perihelion In February, 1912. Encke\ celebrated comet was rediscovered or July 18th, in Gemini. It jrn never vie Ible to the naked eye. It ie celebrated a the first short period (3.3 years) cornel discovered; also because, its shortening period was thought, to indicate a resisting medium in space. This is now at tributed to the retardation caused bj crossing meteor streams, ac the retord&tion is not constant, but occun at two points only. It may seem a paradox that retardation should expedite the comet, but it does; for il causes the oomet to fall slightly nearej to the sun, and, hence, to move fastor. Th» oomet is also believed to vary in brightness with the eun spot cyck. The Transvaal Observatory has beer following Jupiter's faint satellites. VI, and VII. are' easily photographed, being abdut the 15th magnitude, bul VIII. is of the 17th, and a difficult ob ject. It is found to bo pursuing th« pnth computed by'Mr Crommelin verj accurately. The Transvaal plate* caught many Asteroids, several ol which were now. Over 700 Asteroid* are now. enrolled, and over 100 awail eCMitlay before being placed. The great Yerkes 40in telescope htu been used lately to determine th< parallax of stars with high accuracy The observers averaged one star pai fi&e night. They find that retinue star ore very remote. Of four tested three yielded no Darallax, and th< fourth scarcely any. These were 4tl magnitude efars, and they were as dis tant as other stars of tie 9th magni tude in the same region. The photography of the whole ekj » now far advanced. When com ploted it will bo a great treasure t< posterity, enabling movements to b< detected and measured. Great laboui is involvod. In each region a kind ol skeleton of etars has to bo optical!} measured and located, to sorvo as tri£ (stations, and corner pegs whence t< etart measuring tho myriads on th< plates. The measuring on th< plates is constantly going on and over 2,000.000 have been piaced Meteor train/; have been seen by t!» naked eye to persist for a quarter oi \

an hour and more. With a telescope they may bo seen much longer, and many trains can be seen with optical aid which escapo tho naked eye altogether. These trains seldom lie lower than fifty miles from th© earth. Tho air pressure at fifty miles is one twetbousandth of that on the earth's surface, and at 100 miles probably only ouo four-thousardth. In this region the trains occur. It is supposed tho train consist* largely of a highly ionised streak, the friction and waste of the meteor producing the ions, and their electric charge. The streak of ions would become a conductor, like rarified gas in a tube. The trains drift, and twist, and curl into all manner of shapes, in the winds and eddies of those high regions. Jupiter's presence in the evening eky warrants a few particulars about him. His diameter is fully eleven times greater than tho ea<rtih's, and his bulk 1400 timos greater. Ho is about halfway betweon the earth and the sun, ; which is about a thousand times larger than he. The white parts of his "belts" shine with a light just equal to what clouds would reflect. These "clouds" have no relation to the sun. They appear on tho east of tho planet, after having passed round the night vide, just as dense as they were at mid-day, and with no more ebango than would have occurred during tho same length ,of sunshine. This shows tbat they ore raised by the heat of tho planet. The . "Great Red Spot" in tho Northern ' temperate zono of Jupiter has [ persisted, with more or loss intensity, for tihirty years, and has . appeared on and off for centuries; It takes five minutes longer in its rota- [ tion than tho equator. This peculiarity tho planet has in common with the sun, whoso equator appears to rotate in half the timo that regions near the ' poles do. These amazing facts are .to , the cosmoganist what rudimentary • organs aro to the biologist. They spoak of ancestral history. The outer shell of the sun and the planet seems * to be composed of swiftly moving 5 matter that had settled down on an ancient core that had a slower rotation. ; The friction-must be tremendous, and a ' great source of heat. The red spot is 1 neither above nor below the general surface of Jupiter. In 1891 a small ' dark spot in the same latitude was v * observed to be overtaking the red spot. It was carefully watched to see whether it would cross over or dive under or 1 coast round. After months of pursuit ( it caught up and began to coast round, but got wrecked and lost on the voyage. ' Thie seems to prove that the red spot is an area of up-welling. It is like a J great spring boiling up in the middle of a slow stream. Tho dark spot was like j a bubble, or a patch of froth, sailing I down with tho current. When it reached the spring it began to ooast round, but the disturbance was enough to break the bubble, or disperse the froth. Tho spectroscope shows that Jupiter j lias an atmosphere above his clouds,, just j as tho earth has. . The dark belte t appear to be lower than the white ones. The "air" appears to be deeper over these dark bands, and the spectrum yields a cherry red, which sugj gests internal heat. Saturn, though he received but one 80th of our eun's heat and light, and littlo more than a fourth of Jupiter's, shows the same } persistence in his "belts." His seasons r are more striking than ours, but they make no difference to the clouds. The rings cast a semi-eclipse "over - vast \ regions for years, but that does not 5 affect the clouds. They must bo the . result of internal heat. 5 Professor Lowell considers that, for a j long period after the oceans settled down on tho cooling earth, it remained p hot enough to envelope itself in clouds. 7 Its seas, were kept steaming from pole to pole; The light of the sun was x that of a very dondy day. Rains were s incessant and torrential, and geological j processes were hastened. Vegetation grew rank to tho very P poles, for tho temperature was ihde? x pendent of tho sun. v This condition, a he thinks, lasted till the coal measures , were laid down, the carboniferous 8 epoch ended with the clearing of the sky, and the beginning of the seasons, t Two facts support this view. The t first is that no annual rings of growth t are discovered in tiio trees of the coal 5 measures. They grow right on withi out seasonal change. The second ie , that the descendants of the plants and 8 trees of the coal age, ench ac tree 0 ferns and many others, still love tho 1 shade and the steamy atmosphere. t .