The Spectroscope And The Stars

At the last meeting oí' tho Royal Asronomical Society, Dr. Higgins, tho em nont spectroscopist, nítido uu extraordiïiirv statement respecting tlic motions ;tking piuco axnong tho stars. The reults he announces are so wonderful that t will bo well briefly to explain how they lavo been obtained, as wcll as their rela ion to what had formerly heen ktiown ipou the subject. Our renden are doubtess awaro that thg stars aro not really ixcd, but aru known to bo traveling wii'tly through spaco. To ordinary obervution tho stars seera unmoving ; nor ndeed oan tho astronomur recognizo au y igns of motion save by prolonged obserrstion. But it' tho exact placo of a star be oarefully determined at any time, nnd agaih tnany year later, a measurable pluoemout can bo recognized ; year after j year, century at'ter eentury, tho motion thus detennined proceeds, uatil at length the stur may be removed by a considerable are (or what is so regarded by astronomera aoonstomed to deal with the minutest displacement) from the position it had formerly ocoupied. But, in general, these luovements ufford no meana of estimating the real BATE AT WJIICII THE STAKS TBA.VET through space. In the first plaoe a star might bo moving with enonnoua rapiditov.-iird or from the earth, and not Boom to be quite flxed on tho star-vault - just as the light of a rapidly approaching or recoding train soems to oceupy an unohanging position it' tho train's course is at the moment in the directio . of tbe üi.i' of sight. It is only what may Ie called the thwart motion oflbe tur.s that the astronomer ean reeögnize by notiiif.' stellar displacements. But oven this motici.m be annot estimate- in miles per Becond, say - nnless he knows how far otl' ■ il in ; and astronomen) know in truth vti}r little abont stel! ar distances. ■ , it seems ut lirst .siglit altogether liopelcsB to atteiupt to meaeure the cate at which ív stur is approaohing or rece i ing. Xo change of brightness could 1mlooked for, nor, i.deed, oould any observed change bo tnisted as an evnlenoe oi' nhangi d distanoe, sinca stars are liable tu real changos of bnllianuy, much as our mm is liable to bn more or less spot marked. Hut, THE DI8TANCE8 OF TIIi: 8TAK8 aro so enormrus that no conceivablc rate of approach or recession oould affect their brilliancy discemibly. Only the most riiji'l thwart motions yet recognizod, would oarry a star over a space pqual to the moon's seeining diameter in 900 years, so that n oorresponding tnofion of n 0688 or approaoh would ouly uhunge a star's distanoe to about the samo relative extent, ind it is obvious tlitit such a change could not nuiko n star, oven in that long period, change appreeiably in brightneec It will seem, then, utterly inoredible that astronomers have laamed not merely whether certaiu stars are receding or appreaching, but have actually been unabled to determine respecting tho 'iiorf; obvious thwart motion, viz : the iato at which tho motion ttikes place. This ie rendered possible ty wliat is known of the nature of light. Light truvels through spaoe in waves, not as a direct cmanation. Now, let us compare a star's action in emit.tnig such waveg with souio known kind of wave action, and we shall at once recognize tho effect8 of veky ravii) motion on tue btab's tart. Conceive a fixed paddlo wheel turning at a uniform rato in water, and that every blade as it reaches the water raisos ono wave, that wave transinitted in a iven direction. Then there would be a siiccossion of wavos separating from each other ly a constant distance. But suppose tho paddie whoel itself to be carried in the given direction. It is olear thut at'ter one blade lias raisod its wave, the next blado, doscending in the same timo as before, will reach the water closor to the preceding wnvo than if the paddie wheel had been at rost ; for the moviug wheel will havo carried the blade closor, so that now a succession of waves w ill result as before, but they will have their civsts closer together. And, obvimisly, if the wheel were carried in the contrary direction, tlu wave crests would be farther apart than if tho wheol had been at rest. Thus reverting to the stars, we infer that if a star is approacbing, the light whioh comes to us from t will havo its waves clofer together than if the utar were at rest, and vioe versa. Jíow, the distance between the wavo crosts of light sifínifitis a diffarence of color, the longer waves producing red and orange light ; waves of medium light yellow and green lights, aud tho shorter waves producing blue, indigo, and violet light. So that if a star were shining with pure red liglit, it might by approaching very rapidly be oansed to appear yollow or even blue or indigo, according to the rate of approach. While if a star were shining with puro indigo light, it might by reoeding very rapidly bo caused to appeivr grein or yellow, or even orange or rod. But, stars d not shino with puro colorod light but M-itlx a mixturo of all tho oolors of the rainbow ; so that the attempt to ostimato a tars rate of approaoh or recession by its color would fuif, even though we knew the stur's real color, and even though st;;rs moved fast enough to produce color changos. The npectroscopist lms, however, a much moro delicate meana of denling with the matter. The rainbow-tintec streak forming a star's speotnun is crosaei by known dark linea ; and these servo af VEBITABLB MII.Ii-MAHKS FOIt TUE 8PBOTRO8COPIBT. If ono of these linos in tho spectrum cii any star is seen to bo shifted toward the red end, tho observer knows that tho stai is receding, and swiftly ; if the shift ii toward the violet end lio knows that tlio star is rajidly approaching. Nmv, Dr. tluggins 'ii'.s hci.'ti abk', nearly four yearR ago, to npply this method to the caso of tilt; bright star Sirms, though his inntrumental ineuns wer not thon sufficieut to render liini quitu certain as to the result. Htill he was alile to nnonnoc with BOine degree of confidinco that Sirius is receding ut a ruto exoeeding 20 milrs per spcoiul. 1 11 urdtT that hu mighl extend the method to other sturs. the Itoyal Society placed at his disposal a fine telescopu, 15 inohes in aperture, and specially adupted to gathei aa muoh lKht as possible with that aperture. Suitable speoto'Copio appliances win uIro provided for the delioato work Ir Huggins was to undertake. It was but lust winter thut the instruUient was reody for work ; but already Ur. Huggiiiü hns obtained the tlO8T WOKDBEFCL tfK".v-j PÉOltfÖÖ PTARS with itsaid. Iïe flnds tlmt inany of the stars are traveling fur more swiftly thun hnd been snpposed. Arcturua, fot examplo, is traveling toward us at the rute of (i miles per secori'l, and as his tliwart ■notion is fully as great, (for this stnr's distance han been iVtimated), the antual veloeity with which he is spceding through spaco can iot be less than 70 milos per second. Other stars are moving with corro;ponding relocities. But omid the motiims thus deteoted 1 r. Buggine has traoud thu higns of law. t'irst, Iip ciui tj-ace n, tetldency among the stars in one part oL tha hoavens to approauh the oarth, whilo tho stars in the opposite part of the heavens are receding from us ; md the stsrs which are approaohiag lie on that s:da of the heavenu toward which Herschc-1 leng sinco taught us that the sun is traveling. But there are stars not i. ving tliis simple law ; and among the-o l)r. Huggina recognizes Lnutancea ot' tlint ooiunmnity ot inotion to whioh u modern student of tho etars cas givon the name of star DRirt. It happens, indeed, that one of the most remarkable of these instanoes relates to tive well-ltnown stars, which had been partieularly pointed to ns forming a ■ irifting set. It h'l been aagerted more tliau two years ago that certain five sturs ut tL-e Piough, ot Chariea' Wain- the stars kn.wn to tstronouicrs as Beta, Gaiuiimi, Delta, Kpsiloü) utiil Zeta, ot' the Great - are drii'ting bodily (hroMgh spaco. Tho announoenient geemed to I many very dariog, vet its author, trust in the mathematicftl aimlysis ot' the eviilence, expressed unquestioning oonfidenoe. Ho asserted, moreover, tbat wheaver Dr. Iliiggins applied the new method of research lie ■would find that those fivo sturs itie either 11 approachins or all reoeding, a;l nt tlie paiue rate, frora the earth. The result has jnstified his oonfidenoe as well in his thoory as in Dr. Jluggnn' uiagtery of the iu-w muthod. IhosA five Btarl are found to be all receding from th earth ut the rate of about thirty miles rr sccoml. Thia reeult al once ülintr.it.'s the interesting naturo of Dr. Huggins' discoveries, and affords 1 BOMISE OF Í1 I &&% ttEVEtATIONS eveu moro intereeting. Tho theories hitherto accepted respectiug tho constitution of the Btellar universe have 'i Miirtj yroi eed with a result deoidedly in favor of the latter. We may f n assured that the matter will not rest hero. A sim 1 and decisive pipce of evideuoe, src'i a that we have dusoribed, will invite maiiy to examine afresh the thooriee respeoting the stcllar heavens wkich have so Long been received unquestioned. The theory of star lirlrt is aesociated with othere equidly novel, and whicli adroit equally well oí boing put to the test. We venturo to predict that before many years have passed, there will be reoognized in the star depthe a variety of constitution and oomplexity of arrangotnonts startlingly Oontrftsted with the general imifonmty of struoture reeoguized in tlio teaehings at present accopted.