ASTRONOMICAL NOTES FOR DECEMBER 1915.

Pukekohe & Waiuku Times, Volume 4, Issue 115, 1 December 1915, Page 1

ASTRONOMICAL NOTES FOR DECEMBER 1915.

(Contributed by Mr L. J. Comiie.) THE SUN The sun's path this month lies in the constellations of Ophiuchus and Sagittarius. .All this month the sun will iise nearry thirty degrees to tbe south of east, and set a corresponding amount south of west. The 23rd is the day of our summer BOltiee, on. which we have our longest day—one of fourteen and a half hours, it is worthy of cote that the sun of the longest and (f the shortest dayß is exactly twenty-tour hours. I HE MOON The phases of tha moan are:— December New mcon 7th 5.34 am First quarter 13th 11.8 pm Full moon 22nd 0.22 a m Last quatter 30th 0.29 a m Perigee 7tb ]pm Apogee 21st Noon Distance at Perigee, 221,700 miles Distance at Apogee, 252,600 miles There has been considerable, discussion io English astronomical circles lately as to the origin of tbe lunar craters, which may be seen clearly with an opera or field glass when the rncon is but a few days old. Of the two theories in the field, one assumes that tbey are the result of volca&ic action, while according to the other they have been caused -by the impact of celestial bodies or of meteors. It is a well known fact that the moon is devoid cf any appreciable atatmosphere; consequently meteoric bodies are not burnt up as tbey are when they encounter our atmosphere, but strike the moon's surface with a velocity of perhaps hundreds of miles per second. As will be seen ftom the following table tbe moon rises in the lata evening during the festive season. The angles given represent tbe angular distance from ths easttowards the north at the moment of rising. December 22nd 7.54 p ni 33deg 23rd 5.34 p m 30deg 24 th 9.9 p m 25deg 25th 9.38 p m 20deg 26th 10.5 p m 14deg 27th 10.30 p in 7deg 28th 13.55 p m East PATH OF THE MOON On the evening of the Bth the moor, a day and a half old, appears in the west beside Venus. Given a clear night this should be an interesting conjunction, but one must look Boon after sunset. Two nights later the moon is in Capricornus, when the line formed by Altair and his two companions points almoßt directly to it. On the evening of the 13th the mo:n, exactly half full, will not be far from Jupiter. Un the 17th it will bs in Aries, while on the two tallowing evenings it will be near the Pleiades. On the 220 d and 23rd, when on the wane, it may be seen near Saturn; oi\ the latter evening it is close to the twins, Castor and Pollux, also. On the early morning of tbe 27th it will be closa to both Regulua in the Lion and Mara. MEKCURY 'lne conditions for viewiug Mercury will not be favourable this month. At the beginning uf tbe month it riseß shortly before the sun, while shortly after the New Year it becomes an evening star again. VENUS, in Sagittarius, is unce more appearing as the beautiful evening star. All this month it sets an hour and a half later than the sun, and on the average twenty-, eight degrees Bouth of west. Venus is already a brilliant object, being about six times as bright as Snius, the brightest of all fixed stars. MARS, in Leo, near Kegulus, has returned to sojourn among the evening stars for nearly b year. On the Ist it rises at midoight, while by the end cf the month it may be seen by half-past ten. Its rising point is gradually approaching tbe east from the north, being distant at present about nineteen degrees. Un tbe 13th it is at its closest to Regulue, when it is two and a-half degrees to the north of the latter. It should be known that Borne appearances of Mars are more favourable for observation than others. This appearance is not one of the beßt, the dext really good ' one being in 1924. The reason for this is that the orbits of Marß and the earth approach much more closely some years than others. At the end of this month Mars will he four limCs as bright as Regulus. JUPIIER, io Pixes still ornaments the evening sky. At present he disappears a little to tbe south of west at a quarter to one in the morning, while by the end of the month he will not be visible after eleven o'clock. His motion relatively to the fixed stars iB very slow. In tact he remains in the constellation of Pixes until next June. He will gradually approach Venus until on February 14th next tbe two planets approach to within half a degree of each other. SATURN, in Gemini, near the twins Castor and Pollux, is now an evening star, and will be favourably situated for several months. It appears twentyeight degrees towards the nottb at twenty minutes to ten at the beginning of tbe month, and rise*

itarlier each succeeding evtriirg until by the New Yetr he is visible at half past suveo. In the matter of eiza Saturn is only surpassed by Jupittr among tf.e planets. He is about 600 times as Jat ge as our earlb, and distant from us nearly a thousand million milas. Saturn has an elaborate retinue ot satellites—no lewer indeed thin ten—but cone of them are visible, except in telescopes. Two of these were discovered by photography in 1898 and 1905 respectively But by far the m:st interesting feature of Saturn is the wonderful system of rings by which hi ia surrounded. ! When Galileo directed his first telescope to Saturn he cjuld see, not the rirgf, but two faint stsrs on either side. His instrument was not sufficiently powerful to show the whole rings. A tew yearn later the two stars bad disappeared, and people said he was mad. But what happened was ttiia: thJ rings oscillate to and fro, and at intervals of 15 years present their edge to the earth and become mvitiblefor a short period. Ihe next lime this occurs is in 1923. UKANUS AND NEFfUNE In tbess notes 1 have seldom referred to Uranus and Neptune, the two outermost planets of our solar system, for the simple mason that they are never visible to the naked eye. But.the story of their discovery is one of the most fascinating in all the snnals of astronomy. In the middle of the eighteenth century a young German soldier cf the name of William Heracbel deserted to England. He was appointed organist to the Octagon Chapel at Bath, and occupied much of his spare time in making a very perfect reflecting telescope. In a telescope ail stars appear as points, whereas planets have an appreciable disc On the 13th ot March 1781 Herschel's attention was arrested by an object which had a perceptible disc. A few night's observation soon convinced him that ths object was not a comet, and that he had actually discovered a new planet. This was the beginning of a great astronomical career for him, for King George invited him to the Court, and gave biui a living at Windsor. When systematic observations of Uranus, the new planet, had bsen made for some years it was found that it did not move uniformly in its orbit. The supposition was put forward that a large planet even more distant tban Uranus was the cause of (he disturbance. Two illustrious mathematicians, Adams of Cambridge and Le Verrier of Paris, both separately undertook ' the difficult task of calculating the position of this hypothetical planet. The untrained mathematician can form no conception of the magnitude of this undertaking. Months of profound thought and laborious toii were necessary. But eventually, when their task was com- ( pleted the telescope was turned to the apot where the figures indicated the planet should be, and there, sure enough, was ihs body { we nsw know as Neplune! Although a planet of no particular, telescopic interest, the discovery ot Neptune will always be remembered as the greatest triumph of modern mathematical astronomy. TflE FIXED STAKS.

The most interesting portion of ths whole heavens is now being truned towards us in the east. Amos implores Israel to "seek him that maketh the seven stars and Orion," stars which we may now view to advantage. The "belt" of Orion is so well known that I need not give any directions for finding it. In fact it is generally used as a landmark from which all the surrounding constellation can be traced. It consists cf thiee equally bright second magnitude -stars in a straight line. The middle star is equidistant from each of«the o-'i«>r two, the total length of tut -elt being two and a halt degrees. A line drawn through the belt at right angles to the latter meets two bright stars one on either side of the belt, acd er,ch about three times the length of the belt from it. The upper of these is a bluish white gem known as Kigel, while the lower star is ruddy and receiveß the name of Betelgeuse. The left hand member of the belt and Betelgeuse forms the base of an equilateral triangle at the northern apex of which we will find Bellatnx, a line from which, parallel to the belt, carries us northwards to another ruddy star, AHebaran, ar.d, if continued an equal distance, to the seven stars of the Pleiades, with which every English boy, ib as familiar as we are with our Southern Cross, The group is a .very small one indeed, and to most eyes six stars only are visible. On clear, moonless nights the seventh appears, and on one occasion I have counted ten. Alcyone, the brightest object in the group—aud a third magnitude star—occupies the centre. The group is in the constellation of Taurus the Bull, of which it is supposed to represent the shoulder. Aldebaran is in the Bull's eye, while Beta Tauri, one of the Bull's horns, is at the lower apex of a equilateral triangle, of which the line from Aldebaran to Betelgeuae is the base. If the belt is produced southwards for twenty degrees we come to Sirius, or the Dog Star, the brightest of all fixed stars. He is the principal star of Canis Major, the Greater Dog, while Proocyon, the gem of the Little Dog, or Canis Minor, forms an equilateral triangle with Betelgeuse and Sirus. A line from Kigel through Betelgeuse. curved slightly to the south, will take us through Gamma Geminorum, and the present position of Saturn, to Pollux, one of the Twins, His companion Castor is Bome five degrees away towards the north.

j Another sweep from Kigel through Bellatrix and beta Taun leads down to L'apella in Auriga the Ihanateer, or.e of the brightest stars of tha northern sky, Unfoituaately it never rises very high in these latitude.", and in the South Island is never seen at all. All thiß region is lull of blight stars, and has much romantic interest attached to it, of which time and space forbid further mention. To anyone interested in star-lore 1 can confidently recommend a little book in ths People's Book series called "The Science of the Stars." The price—tightper.ee—-should be within the reach ot all.

The following table of astronomical data for December Ist should be of material assistance in locating the stars just mentioned. The angles given represent either the altitude of the stars at the particular moment, cr its angular distance from the east or west when rising or setting. Thus W 33 degrees S denotes thirty-three degrees from tha west towards the south. The angles are constant for ell time but the times must be diminished by halt an hour per week:— p.m. Rigel E 7.9 14deg Alpha Crucis S 7.36 14deg Fomalbaut W 8.48 66deg Achemar S 8.49 70deg Sirius E 9.28 28deg Alpha Centauri S 9.48 Bdeg Alcyone N 10.66 29deg Aldebaran N 11.45 37deg Capella N 12.24 7deg Kigel N 12.24 61deg Sirius Rises 7.10 E2l deg & Betelgeuae Kises 7.15 E 9deg N Altair Seta 825 W lldeg N Prccyon Riscb 9.10 E 7deg N Capella Rises 10.0 E 65deg N Pollux Kises 10.40 36deg N Castor Rises 10.45 E 40deg N RegulUß Rises 12.0 E 16deg N