POPULAR ASTRONOMY

Otago Witness, Issue 2803, 4 December 1907, Page 66

POPULAR ASTRONOMY

I<m NOTES FOR DECEMBER. Bt Rev. D. Dtjtton, F.R.A.S., F.G.& The Bun enters the sign of Caprioornue on December 23, and occupies the constellation of the same name from January 18 to February 14. The Moon will be new on the sth, first quarter on the 12th, full on the 20th, last quarter on the 28th. The Planets.— Mercury is a morning star, Yenuß is an evening star, and may be noticed in. the western sky after sunset. Man is in Aquarius, and sets near midnight. Jupiter is coming into view late in the evening above the north-eastern - horizon. Saturn is nearly stationary in the eastern portion of Aquarius. The Cbnstellfttions.— Orion is now so conspicuous between the east and the zenith that no one can fail to locate it. Above Orion, and near to it, is the small constellation Lepus (the Hare). Canis Major, with the great Dog-star Sirius, easily arrests attention, well up from the eastern horixon. This constellation figured very prominently in Euphratean astronomy. Among the remains from the mounds and rums of ancient temples it is frequently found sketched as a dog standing on its hind feet in the act of springing. after the Hare. Taurus (the Bull), with ite ruddy star Aldebaran, is seen between north-east and north, and a little lower down and farther north the Pleiades are easily found. About 10 ©'dock Oanis M ; nor (the Little Dog), with ite bright «tar Procyon, can be well observed above the horixon between cast and north-east. Thw constellation suffers by comparison with its rich relation Canie Major (the top dog). Procyo.n, however, is no mean "star j it holds rank among the 20 brightest sUrs in the heaven*. lake Siriue it is one of the near stars, sending it* light to us in a little more than 10 years. It is * double star, having a companion of about the twelfth magnitude whioh goes round it in 40 years. Pegasus may *81l be se9n in the early evening towards the horiion between north-west ; and west. Looking southward, the Cross | will be noticed rather low -down in a south-eastern direction with Alpha and ! Beta CenUuri on the right-hand side, and nearly south. The triangle is above these stare to the Tight of them. Argo (the Ship) b well afloat above the southeastern horizon. Canopus, at a much higher altitude, is in the same direction and cannot well be mistaken for any other star. The bright star to the south-west of Canopus, and not quite so high, » Achernar, the chief star in Eridanus. - Skirting along the northern horizon below the Pleiades is a part of the constellation Perseus, it is too low down to be well seen in our latitude. As a star-group it is notable for ite beautiful double starcluster, and especially on account of its remarkable variable star Algol, the Demon star— the "Blinking Demon" of the Arabians, so named probably because they noticed the extraordinary variations in its brightness. The ancient astrologers regarded it as the most violent and dangerour star in the heavens, the Chinese gave it a name which had the gruesome meaning of the piled-up corpses. The Hebrews called it Satan's Head. It has always had a bad name, and never had a friend to speak a good word for it. Algol goes through very rapid changes. It is a star of tho second magnitude for two days and a-half, then it begins to decrease until it gets down to the fourth magnitude. It i lemaina at that for about 20 minutes, then I begins to increase in brightness until it is book again to the second magnitude; and thus it goes blinking on, all its variations occupy about 10 hours. Ite mean period is under three days, and all ite changes are visible to the naked eye. The cause of thie strango behaviour was long suspected to be due to the /presence of a rapidly revolving dark satellite partially eclipsing its primary, and this has been verified by spectroscopic research. On the night' of February 21, 1901, a new temporary star suddenly blazed out in Perseus. A photograph happened to be taken of that region on the previous even- ' ing, and there was then no sign of what was about to appear. No one was expecting anything unusual. The following night the new etar revealed itself to 'several

observers, notably to Dr Anderson, of Edinburgh, who bad already a reputation for quickly seeing new things in the sky. In three days this new etar became the brightest in the northern hemisphere. It quickly diminished, and in less than two months it sank to the fifth magnitude, and by 1903 it had become a faint nebulous object of about the twelfth magnitude. Professor Newcomb 'estimated that within three days the light of thk star increased ten thousandfold. There are - numbers of recorded appearances of new stars, and many' theories hare been put forth to account for them. Lockyer holds that all new ~ stars are due to the collisions of swarme of meteors. The theory which attributes them to the movements of dark bodies through the nebciloue matter whioh 16 so widely diffused in space appears to be most in agreement with the results of spectrcscopio mvestigatiop. Stars, both luminous and dark, including our eolar system, are wandering through space at velocities of many millions of miles a year. Collisions among them are not improbable. Many astronomers think that ihe dark stars are more numerous than thi bright ones. Stars are not only being born, but many are dying, and doubtless not a. few are dead. Our Sun has hundreds of dark bodies revolving round him, including ,th<* minor planets, besides . innumerable swarms of meteors, and we have no reason to suppose that the eolar system is exceptional in this respect. ITEMS OF INTEREST. The brightness of the' stars cannot be regarded as a test of distance. This i> illustrated by the two great stars visible in our eastern end south-eastern «ky, Sirius and Canopus. The former is the brighter of the two, and its distance from' us is about 8£ light-years, while the light from Canopus takes at least 296 years to reach us. This distance is practically immeasurable; hence, great as Sirius is, it is yet & mere pigmy compared with Oanopus. Alpha Oentauri is a double star, and the pair can easily be separated by a moderate telescope. We gain some idea of stellar distances when we remember that this star, though the nearest of all star* to as, appears to the naked eye single, the two stars blending into one; yet they are separated from each other by about 23 times the distance the Earth is from the Sun. Beautiful photographs of the Zodiacal Light have recently been secured. This light is an effect, probably due to the re* flection of sunlight from the countless number of small meteors which occupy the space inside the Earth's orbit. It is a faint, and diffuse stream of light, and in appearance somewhat like parts of the Milky -Way. It ma- be seen in the early morning or evening stretobing up' from the sunrise or sunset points of the horizon along the ecliptic, and following its course for many degrees. It may be seen at any season of the year when the horizon is clear, but is seen to greatest advantage on spring evenings and " autumn mornings. The spectroscope has proved that the light ia reflected sunlight. The .planet Jupiter, which is now an evening star, is one of the most interesting celestial objects to the - possessor of an astronomical telescope. Not only are the four Moons, whioh so greatly delighted Galileo, easily seen, but also the wonderful cloud-belts of various delicate tints much stretch across the planet. The watcher may be rewarded by the sight of an eclipse of the satellites by the shadow of the great planet, or, more interesting still, a. transit of the Moons across the great diio. The cloud-belts are frequently noticed to be in rapid motion. Jupiter is the giant member of the solar system— l3oo times larger than the Earth, though it is not proportionately heavy, being about 316 times tho weight of the Earth. Its distance from the Sun is more than five times greater than ours, and its year is nearly as long as 12 of our years. The diameter of the Earth is under 8000. miles; recent estimates give the equatorial diameter of Jupiter as over 90,000 miles. The "Earth revolves in 24 hours, while Jupiter, whioh is. over 1000 times larger, rotates in less than 10 hours. One of the most interesting of the markings is what is known as the great red spot. This object came into prominence about 30 years ago, and, though ft has fluctuated in colour and visibility, it still exists. What it is has not been determined, though many explanations of it have been attempted. More latisfactorj statements as to what ifc is not are available. "It certainly does l»ot represent the outpourings of a great volcano; it is inno . sense attached to the surface of the planet, if the planet baa a surface (which is very doubtful); it is not a disclosure of •• glowing mass elsewhere obscured by rolling vapours." All these things it is not; but what it is nobody knows. The rapid motion of the oloud-halts indicates for the planet a great internal temperature, which v not due to the Sun. At the. distance of Jupiter from the Sun solar heat is only about one twenty-seventh what it is on the Earth, and is therefore incapable oi forming those dense cloud masses which are observed. The planet is doubtless, in a very immature stage as a world, and probably has not sufficiently cooled to have formed anything in the nature of a solid crust. We may consider that it it midway between a «un^»l«» .nody and * world like cur own. The idea that tn« planet is a glowing body giving out inherent light has not been confirmed. It. spectrum is that of reflected sunlight, though as Serviss says: "Not very long ago, as time is reckoned in astronomy, our Sun, viewed from the nearest star, may have appeared as a double star; toe brighter component of the pair being the Sun itself, and the fainter one the body now called the planet Jupiter." Jupiter has seven satellites. Four, which are of I 3ons'derable size, have been known from ! tho time of Galileo, and the three Atm i ones have been discover©* at the Lick Observatory-the fifth in 1892, tho sixth at the end of 1904. and the seventh at the beginning of 1905. The two latter weredw covered by the aid of the camera. The* have be§n photographed «ucoeesfully at | Greenwich. _ The Westport Coal Company's output last week was 13,636 tons 3cwt. Mr Frank W. Eraser, of Scone, N.S.W., writes :— JT I was louring New Zealand «ome time ago, and owing to the continued wet weather contracted * yer 7 •« vero ETfc While staying at the Royal Oak, mW* lington. a friend advised me to try Chamberlain's Cough Remedy. This advice wa« followed, and after I had taken a Jew doeeg I was completely cured. I can confidently reoommend Chamberlain's Oough Remedy to anyone suffering from throat or luu* U'oufrleg." For §al§ everywhere.