IN STARRY SKIES

Evening Post, Volume CVIII, Issue 50, 27 August 1924, Page 9

IN STARRY SKIES

ASTRONOMICAL NOTES

THE SOUTHERN CROSS

. (By. "Omega Centauri.") The purchase of a fine telescope by tlw City Council, and its erection just.! ay the^ time of. an unusually favourable': opposition of- Mars, ' will doubtless do ! much to arouse popular interest in I astronomy in Wellington. It is , well, ! for those who intend to study the hea, j yens through, this or any, other telescope to be familiar, with the constellations as seen with the naked eye, or with the help of field glasses. The. revo •latioris of a large telescope will be much j more fully appreciated -if 'the. objectb i have first been studied with lower pow- > ers. '■ ■ '".,''"... ; .'" ."■■ Of the constellations visible here, the Southern Cross is the best known and most easily, found, and it affords "an excellent starting point when learning the others. At 8 o'clock this evening it may be seen in the south-west, lyine: on its side about 30 degrees above the honzon. Tlie top of.the Cross is then/ pointing to_ the west." Above it aro'tlioI two bnght'i stars, Alpha and Beta Ccntaun, known as The Pointers, bacause the line joining them when produced .passes through the upper portion oi the Cross. ■■■'■ , • \x - Alpha, the brighter of'■ the two, "is tho pointer farther from the Cross, and when' exammed turns out to be not one singl* sfar but almost interesting system. Quite a small telescope, is sufficient to : divide the image into two points' of light, which tell us tljat we, are looking ■w., af^ ou fi ble*l? r-- -This- hinar >' s >-st™ ■w pc first discovered in the Southern Hemisphere, and.the first1 whose distancefrom the sun was successfully 'determin-• ed ihe paic is sofar from us that its i ngiit takes, about, four .years and four! months to reach us, though travelling i at the : rate of 186,300 miles per second Until.eight years ago this system wa» ' heheyed-to be nearer to the solar system^than any other star, but in 1916 a' taint red telescopic star was - .disctwe ed, w^iich appears ,to dispute th» ' claim _of Alpha to .the honour. The ne\v:: rival is called Troixima Centauri. {) .Ihe components bf Alpha are in re-'' ality two guns very like'- our own. They circle round one another in about 81 years. Proxima is believed to be phvsjcally, connected with this and possibly revolves around it in about a~ milhon years; Being at present on the side of its orbit which is nearer to the sun, it'is actually our nearest known .neighbour amongst tlie stars.' . All the members of the Southern Cros ß are vfery much farther off. The bright- - es* '°£ .'Uiese, Alpha Crucis,. the star which, forms the foot of the Cross, is also a multiple star, consisting, of a close pair; of\bright suns "and •■ four' much fa:nter ; ones..'. The", other- stars of the-! Oross whicli can ..be seen,clearly with the naked eye get fainter as we go, round the. group in the order Beta ! irtimma, Delta j Epsiloh. Near Beta ws can see with, a telescope one of the reddest stars'.in the. heavens. Gamma turns out to be a .group of three or *tiiore, two of which probably are phv- ; sic ally, connectedri ■" "■* /The region of the Cross is rather bare when seen by the,.naked eye/ There is' probably much non-luminous',, matter', llie Ual backus specially.noticeable. A telescope, of course,"-shows very jnanv. more stars, especially around Beta One faint ppint : of; light, just visible to the' naked eye, turns out, when viewed with' a fairly, high' power, v tp--: consist of over on,r hundred and twenty stars.' "Owinoto the beautiful colours of many ol these, it is gerieraUy -- known as "The Jewel Casket." It is most interesting frj compare the images ofv this cluster as viewed through,field glasses, the five- , inch, and the nine-Inch telescopes". - J omega' centatoi. '.'■■■ . ! Not far from the. Southern-Cross is th d most- magnificent globular clusterin the heavens.;.: It. is known as Omega Centauri, and can be seen with theTiaked eye as a rather-faint hazy star In order to ... recognise' it, . start from Beta_ Centauri '.the.fainter, of tlie two pointers, which is the on/- nearer, totl.tCross.. Lobk towards the right,'-"that is m a direction parallel.to the axis of the Cross, and find Epsilon Crucis ratlier more than a. Cross ■ length from ;«eta. ...Go qn;in. the same line: another Crass length, and you reach Ome»a : ' Look with field glasses, and at once itis: evident that' Omega is not. a star \\ith a telescope it. is amost beautiful object, consisting of .apparently innumerable points of light: arranged! witliin a sphere, most crowded towards: the , centre, _and -becoming more widely scattered as we pa-ss outwards in any direction. Although apparently innumerable to.the eye, an estimate can be made with the help of photography. -Magnificent photographs have -been taken of this object, and by. studying the negatives under a measuring ' microscope it - is found that over 6000 points are indicated on the plate. ' . .• .From this it has been estimated that tlie cluster, consists ,of .about1 teii- thousand stars. Other -globular' clusters greatly exceed this in the"'number' of their stars, the cluster in- Hercules', for instance, having, about: ten "■ times' as many, but on account' of its comparative nearness Omega v Centauri is ±ho most beautiful of all. ..With a fairly' low power the city, telescope gives a most impressive view of it; It, is best not to magnify it sufficiently to cut off tl.c dark sky around. r - ' . - ■ - If, .while gazing- at this cluster, we remember that each one of these twink-ling-points, of light represents a sun possibly, controlling a system like bur own, that each is endowed with incon- i ceivable energy,: sending out radiation through the vast domains of space, and , that the \vhole cluster is the scene .of ceaseless_ activity, •we .begin to form ! some quite inadequate conception of the marvels of the universe. -