IN STARRY SKIES

Evening Post, Volume CXI, Issue 143, 19 June 1931, Page 14

IN STARRY SKIES

OTfMILkY^mY

lilt THE SOUTHERN CROSS

AMDr THE XENTAUR

.'(By "Omega Centauri^'):

flic marc, deeply the;'.."lifjav.6n*s ..are fe^udiedrvthV more..clearly does it become- evident that.the. .-stars-'--aw not scattered at: random. -Theyl-show the most- .'nh'migtakable Tevi'denco:.". ofc ' systematic organisation.; Practically everything that "can be seen with the naked eye'bfeiongs to the Galaxy; and- a; giance at the ; star-lit sky shows .lliat.'.this is 80t..& fortuitous assemblagei-.oi;-.stars. Uneir^iing ■■■ the- ivh'olfe' heaven' -is■■'. the

glqi-wusib^d of light we call the Milky--Way. In.quivsurVcj'..with field glasses-we-have takett-itas-^ui: guide to the -constellations.;. We have-iyatehed it as •a> broad stoeain- passing, tie Great;and 'tho.tittle J|bg, -then ■widening out still further in. the. imSiune-. .constellation .of ■ Argo. ■ ; JJfcwi wo saw it-appear to break up-into ;4ngerlike projections until the whole .bright, stream seems to be actually severed by an irregular dark- band. Still within the .same constellation opposing fingers «f light. stretch out from the other side

into.the dark lane. The appearance is that of twp;. gigantic, brilliant hands ali^.pst meeting at the iinger tip.s. The second hand suddenly, .narrows towards the wrist, becoming at the same time much more brilliant. In the narrow and brightest part we see the beautiful :nebula- with the strange dark marking Jike a',keyhole, in its centre. .-On the edge.: of the dark spot, but now invisible to the naked eye, is the celebrated star Eta Carinae, or, as it used : to be called, Eta Argus. Here, last-century, it went through its astonishing, series of changes. The Keyhole Nebula brings us to the region ■ shown in/pur map to-day. It was 'given also in the last map, so it forms a convenient connecting link. Between-.the Keyhole, and.the Cross the Milky. Way attains its; smallest width. To . the ■ naked eyft-jitirJooks-only..about 'three-..degrees ■wide.- But 'photographs, taken, with long exposure, show that the reality, is utterly ; diffweat from the appearance. The-.whole surrounding, region;-to a width .;. of-..- thirty/ to forty v rldegrees is Reen/.to'^ier. strewn ; with innumerable feint stars. But here another peculiar characteristic of the Milky-Way becomes conspicuous. The brightest : parts of the -. streani are often associated with what .Herschel ■ called "Holes '■ in the Heavens^, -The -Keyhole is a smail but typical example of 7 such ■ a .region apparently destitute of stars. Astronomers used, to think thatj in: viewing spots such as. these, they were looking right through the entire - Galactic band and peering into; the. black recesses of space. But now it is .certain.'that the Milky. Way is no mere band of stars that could be pierced in such a way. It is recognised to be a system of stupendous size viewed by us from within. BstiwatesTof its dimensions fiave continually increased until ~ Shapley, suggests that its diameter is some 300,000 light years. .We think~ of' it as a vast assemblage of. scores of thousands of millions ; of suits grouped into innumerable star clouds, clusters, and streams, with planetary nebulae and both bright and dart diffused nebulae, all intermingled and -vs-hirling in a single gigantic flattened ■■■•■sy'steja.- ■■. -We see its fellows, and its likeness, in millions of spirals far beyond its utmost limits. To give it is present formj*two gjgantic cosmic systems seeni to have" come into whirling eoalescence,and Kapteyn has partly unravelled the complexities of motion of the two great streams of stars. As soon as the dimensions of the Galaxy are even .faintly realised, \ttie~idea of

( .. - innumerable: tminois .devoid "of "Stars' all poiiitjhg'.dirfectly: "tJnvajijs J'lio .'solar sys-. tenij .Ueeoines.utteriy un'thinkalijt;,1. Wbjit tliojy'aic t.he.so""dnyk patjUlics." j£ tlicy nrq not^lioVlesT; Barnard, by. photographing thcni^-aml giving.thorn the- uiost careful stu'd^;; seems definitely to.' hayc.proved that'fthoy "aroVc'lbuds".. .of.datk matter that 'hide ' or." obscure •' tlis I light. of' all sta'rs^.ijehiiid 'tHcm. V -The: region..' of the Southern-.Cross, is ail. excellent one in which' \s. nialic'.',.tho"" acquaintance of these..dusky ..cloiicls, for. the best-known .m3'.inQst.:'jelebrated of tfeih all 13 the so-calied Qoal ..Saqk. It-is an 'oval spot'^about. seven, degrees in diameter, abouf..'i.ho'saine. sizo astha Gross itself. Alpha Xlfucis .-lips, on its mai-gin,- and the cloud extends-almost to, Kappa aud then;'sweeps round almost half-way to Beta pcritauri. - Within the Sack- ;m ordinary. -Jpyer; can ..detect only, -a single star.'.v'Cho ■ -rest .of;. the.-space- looks strangely,-.black.".- Tt. .appears; quite dif-ferent-in tono.-;.from:.the. .usual background of..sky... Tliesamo thing i 3 true of all.th.e rdark Ta'nes'and other patches in the Milky Way. show tho whole, space of the Coal Sack dotted with tiny points, of light. If they aye really . sunsy like', those around, they seem to have lost the ..greater part of their brightness; "Tho'Cbal Sack is not by any- means unique. From the EointflraV.on right through the Scorpion and Sagittarius- we see similar dark streaks and- patches'; ' The whole/of the., much wider. stream revealed ; by photography exhibits a strange and significant structure; If you "examine, with a magnifying- glass the glorious .photographs,that have TDeefl taken the."arrangement of the faintest stars suggests the. picture, of

thp ; cells in a section- of a:.plant- seen through .the-.microscope. There: are. innumerable -overlapping, circles .or . ellip-: ses-^dafk :wi'thin .but outlined .by-.stars; This .peculiarity is not restricted- to. one part of .the Milky Wajy but appears to be .a general characteristic. After' passing -the. Pointers,, the .stream,, even as .seen.by.the.-iiaked eye,;..widens out. rapidly i.untii ■it covers - more than. ; :th.e entire length of the Scorpion. It seems at ■ first ■ .to be broken into three separate, streams, but the dead blackness of the;.spaces between-these .sp'on? shows that-airflosj;.;. certainly ;.the;.effect/J is.-pro.-duced-jby ;* dark; .: obstructing - - matter hiding some of th'o. clouds of stars. .-

■ This region of. the sky is full of interest, but most of the. objects have ■ been described, in previous a rticles! It . ia ;>w.ell vWorth-.while to,- ,scau it very i thoroughly; with : 4eld glasses.- We can refer iiow-to. a few only: of the. many •. interesting objects .within the -area of , this map.;. Oniega. Centauri is.certainly one of the most beautiful: of the globular- clusters. -It, is far smaller {than; Ml 3, the:thagnificent;one in■ Hercules, :but- it 1 is so: much aeareri that-, it. appears far . brighter], . It. can be seen easily with the naked eye, and field glasses show at onca.that it is very; different from an. ordinary star.. Large telescopes show that jit,is a swarm of; about ten thousand-suns. : But it is .so far oft' that its light takes; about twenty thousand .years to reach- us, and even so ; there; is only one other known globular duster, 47 Toncani, which is as near , as that, -.: Alpha; Centauri is one. of- the finest double .stars and one of its. components, is. a; sun almost exactly like ours. It waa one of the first three 6tars~wKose distances were" estimated almost simultaneously in 1838, and it is" still' the, nearest naked eye star to i us. Its distant companion, Prosima , Centauri, is at present actually the nearest known star and yet its light takes more than four years to reach us. Kappa Crueis is a lovely cluster of coloured stars, .called by Hersehel, the; Jewel Casket. .It can easily be seen' like . a fsCinfc star, close to Beta Crueis. Alpha and Gamma Crucis are interesting multiple stars. The Pointers and the Southern Cross are-'not 'a. natural group, like the Pleiades, the Hyades, or the stars .of the Great Bear or of Orion. Beta Centauri, for instance, is over twenty times as far from us as .Alpha Cen- . tauri, and Beta Crucis is four times as : far away as 'Alpha Crucis, and nearly a hundred times as far as Alpha Cen--1 taurL- ■ . ■ '