ASTRONOMICAL NOTES FOR FEBRUARY.

Press, Volume LXV, Issue 13336, 30 January 1909, Page 8

ASTRONOMICAL NOTES FOR FEBRUARY.

(By the Rev. P. "W. _ -, airc_oijgh, F.R.A.S.)

After nine o'clock, when it is fairly dark, Orion will bo seen high in the north. To tho left of him, and lower, oro the Hyades, with tho red star, Aldebaran, at ono angle of the"triangle. Lower, and more to the left, is -tlie group of tho Pleiades, like fireflies in a mist. High to tho north-east of Orion is Sirius, the dog-star, and due south of him, Canopus, the next brightest star in the sky. Far below Sirius, and to tho right, is Procyon, in the lesser dog, and far below him again are the Twins, two second magnitude stars, about as far apart as the head and foot of tho Southern Cross. The new planet is in the region of these two stars. Jupiter will be seen rising in the oast in Leo. Last year he was near the Twins, and two years ago lie was near tho Pleiades. These milepost on the sky may help somo readers to understand the journey of the great planet round the sun in twelve years. Ten years hence ho will be near the Pleiades again.

Earthquakes lio on the borderlands of astronomy, and as they are a topic of tho hour, wo may fairly treat of them in their bearing on tho earth, viewed as an astronomical body. At the time of the San Francisco disaster it was said by some that the earth, by getting off her centre of spin, adjusted matters by violent ruptures of her crust. This we' controverted. Part of the minute wandering of the centre of spin is no doubt due the shifting of surface loads by the atmosphere. A continent soaked with rain-and loaded with snow, as compared with tho same continent parched by the heat of summer, presents a difference of load that naturally changes the axis of the groat top by a fow feet. Tho axis shifts to relieve strain. It is not the Shifting, that .causes the strain—quite-the opposite.. Then the change of load in tho process of the seasons is slow and gradual, and tho shift of the pole is also slower If the winter load were dumped" dow_t v in a few seoonds there would be a sudden strain to which the axis could not respond in time, and hence there would be a strain on the earth's crust and an effort to restoro the true balance by rupture. ', Thus earthquakes 01 the spinning glob© may cause other earthquakes, which would not take place if the globe wero not 1 rotating. j

This has been illustrated by a special form of top. Let tho top be tof metal and very, (accurately turned. The body of the top must be a "flat plate of metal with a raised flange round the edge. Set it spinning at a l-igh velocity, and when it "sleeps" drop a ,tiny pellet of steel on to the plate. The centrifugal force will at or-ce fling it against the flange, and the top willr ook and reel. Now drop on another pellet, and almost immediately the top recovers and "sleeps" again. A flash photograph will show that the two pellets are arranged exactly opposite to ono another. This stows that a rotating body having an irritating disturbance of balance on und part of its circumference seeks a similar and equal disturbance elsewhere to restore the balance. If wo drop a third pellet on the top it ■\4iXL rock for a few moments and then run steadily. The three equal pellets then occupy the points of an equilateral triangle. If a fourth pellet be added, they occupy the corners of a square. If instead of the second pellet, two be -uLstituted, each of half the weight of the first, they will lie closo together. Let them, however, be each rather more than half, and then they will lie a little distance apart, with the point opposite to the first pellet u.idway between them.

Thus, a rotating body adjusts and distributes its disturbance with mathematical accuracy. Let us, then, conoeive of the earth as our top. In 1905 an earthquake took place in the region of the lato disaster in Italy. Seven or eight days later the San Francisco shock took place. That was about one third round the globe. Our theory then pointed to the other sido of the Pacific as the *_iiird angle of the equilatiral triangle. In a few days a violent shock took place iii Formosa, and tbe balance was restored. Again, a few weeks ago, the appalling disaster in Sicily and Italy occurred. Some thousands of square miles were suddenly shifted, probably, on the whole, by sinking nearer to the earth's centre. It was as though our top had received a little dent and required,.,other dents to baianco it. The spinning earth began to feci round its continents and sea-bot-toms for weak places and movable regions. California had touched bottom and oould do no more. In a few days, however, Mexico, almost in the same longitude, responded. The shock was not so violent as that in the Mediterranean, but it involved a much greater area. Again we had to look for the third corner of our t.riangio In a few days an eruption was reported from the Filipinos, but no serious earthquake. We may take it that tho strain was felt there, but thero was nothing ready to slip. Then camo the mysterious shock recorded by the seismometers of Europe and India, and now believed to have been'in Chinese Turkestan. The three points, when they are fixed, seem not likely to make an equilateral triangle, but that is nor, necessary if the disturb-

a noes are unequal. Three pellets on our top, if unequal, will arrange themselves into any kind of triangle, so as to baianco on tho pivot of thc top—provided always that no ono pellet is as heavy as tho other two.

Wo sometimes hear of "earthquake weather." It is, however, extremely improbable that an earthquake can affect the weather before it happens. After a violent shock it is conceivable that the weather maybe affected, but in tlie popular sense of tho expression it is fairly safo to doubt that there is any such thing as "earthquake weather." We would suggest, however, that the rotating planet, when feeling after adjustments of balance, may shift, the oold and heavy ocean currents and great masses of ice, and so give us a bad summer.

Tlio discovery of a now major planet is the great astronomical event of tho time. Wo havo as yet no particulars beyond tho first announcement. It is probable that tho planet is not brighter than the tenth or eleventh magnitude, or, say, 100 times less bright than tho smallest star visible to the ordinary eye. In that ovent it is unlikely to have been charted as a star by former observers. Henoo it may not bo possible to trace it backward ns Uranus and Neptune -were traced. Tho former of these is of the 6th and the latter abovo tho 9th magnitude, and both had been often charted. Their orbits were therefore ascertained without waiting many years for tlie slow advance of the planets. Tho new planet is not likely to have a period of less than 250 years, and if there aro no previous records of its position it may be many years beforo tho elements of its orbit are accurately known. If, however, it has beon photographed or seen on several nights, astronomers will already- know its i>resont distance and the approximate length of its year. From its stellar magnitudle, or from the diameter of its disc, if it presents ono, its size should also bo fairly known. That some weeks havo passed without any information on those points is peculiar. It suggests that the object is a very difficult one, and reminds us that tho cable message said only: "Prof. Pickering has obtained evidence of a new major planet, etc.," which is different from saying that he had discovered tlio planet. Possibly the weather has been likft-the weather here, -wholly unfavourable to photographirrg or securing so dim an object.

We naturally assume that the planet is the next in order after- Neptune. But there may bo several Arctic worlds beyond Neptune, and there is really no reason why on© discovered at haphazard, as this ono seems to havo been, should! bo tho nearest, of them. The stranger may bo several times more remote than Neptune and on tho very limits of discoverability. Increasing distance is against tho visibility of a planet in a double-barrelled 1 fashion. Not only is ' the' planet- more remote from the observers', but moro remote from tho sun, by whoso light it shines. Neptuno is thirty times as far from the sun as tlie earth, and tho light is reduced by the square of 30. or 900. Still, a 900 th of our sun light is equal to about 600 full moons. Seen fromNeptune,' the sun 'would look"'like '_[' 1200 candle-power electric arc at a -distance of 12 or 13 feet., Should there be a planet five times as remote as Neptune, tho sunlight reaching it |Would be equal to only thirty full t moons; Now tho earth, as seen from tho moon, is 13 times as Jorge as the moon is to us. The earth is also probably more than twice as good a reflector., as ..'the 'moon. Hence, when we • see the- old moon in the newmoon's arms, lit up by.th©earth-shine, we \see about the effect of the light ot 25 or 30 full moons. Tho outer planets, so far as they are known, are. however, better reflectors than the moon, being enveloped in clouds. One supposed planet, at five times Neptune's distance, might therefore shine two or three times brighter than the' ghost of the old moon does. Still, it would probably be too dim for .-star-' ejed soienoe' to detect.

Recent careful observation has reduced the estimated si_e of some of the outer planets. Wo give a table of the chief facts about them. The earth's distance from the sun, her size, mass or weight, tho light she receives, and her year, aro taken as unity—one. ->«- Sun'a tance. Size. Mass. Year. Light. 2>ay. Tho Earth 1 1 111 24 Jupiter .. S 1850 317 12 25th 9SS Saturni 9 768 95 29. 90th 10 U Uranus 19.3 47 14.6 St 360 th 13 ? Noptune 30 53 17 166 900 th ' 1 The satellites of Uranus and Neptune move backwards, so as to giv_ new moons in the mornings and waning moons in tho evening sky. ANSWER TO CORKEBPONDEN-'. Question, Other Worlds.—Thanks, iv some later issue.