Show UN U N ak rl ty auw aft eil kill 1 mi ai f ASTRONOMY ff unta urta Mt I 1 I 1 proe PROF 0 F ORSON mtr I 1 not ai taba ii ir h LECTURE VIII s ya s rings of saturn an bf offee the planet I 1 and rings staby by boythe oythe of bengs lengs i n s dependent ito ido jr 0 oil 1 tiree three ta uses variety fan pan far bety bedy of satu Sa furman turman r anz a A seasons I 1 wien when tie the ninos rings are eni ini isible phases y q I 1 he tu I 1 jn kyfus gj scenery from the surface of q lk ut fifteen een teats tears total eclipse 4 argit Eight Moons joons their periods ai and nases phases l grahs I 1 arnd arna I 1 its characteristics I 1 6 bf ra gieir anomalous r il Q it on T 4 peculiar liall M p 1 it il yafa dio fio ii i 1 lla lia y satiny or grand objects bt the solar term tern saturn is truly the most wonderful this magnificent orb encircled by a myrten system X of rings and accompanied by eight moons performs a revolution around the sun at tJi emean distance of MG of miles in 10 of our days or ot E in kut lut about years dariz when nearest the eleb earth it la Is of miles distant an interval which child could not be traversed by a cannon ball flying with a velocity of aes ues an hour in less thai than about years circumference of its ito orbit is of miles a distance so great that a steam carriage moving at the rate miles an hour would require above years to complete the tho journey lourney saturn rolls in silent grandeur around this whole circuit at an average rate of miles mlle every eiery hour saturn is nearly as large as jupiter being miles in diameter around this stupendous per pei idous globe are two magnificent rings situated inthe in the plane of the equator and nearly concentric with the planet and with each other the inner edge of the interior several thousand miles distant frow from the surface of the planet and consequently h ha as no contact or connection with it from the inner to the outer edge of we the interior interi oi ring or its breadth is nearly equal to io its distance froni from the planet the interval be bet t tween the Interi interior pr and exterior is IA 1791 miles ero fro froni the li inner to 10 the outer ed edge of the exterior ring or its breadth to 10 miles tha the hel hee thickness of these ring ringa can not exceed emceed miles these ringi hae hareno no connect lon loa or contact with each other let it be understood that cheso thes thea rings do not encircle the planet plaz in the forn torn oa jaroad broad proad road belt ot or zone extending several thousand miles each W ade of the equator but hut burthey they encircle that blo glo glorein globe bein hein in the plane ol 01 of is its equator eti edi witti their edges directed toe tor to ward sits centre contre the dimensions of this extraordinary appendage e as calculated AIt alt dit 4 fram professor strives ves mi measures are as follows fallow 1 fc t 5 1 exterior diameter alameter of exterior ring mue interior do do 2 breadth of I 1 I 1 1 1 I da u exterior il diameter limiter of interior ring interior i ido ado i do do 14 breadth of do 11 equatorial diameter of the planet I 1 Is later interval I 1 between the plane planet tand and the d interior rind ring A interval erval enval between ahe the r rings ings 4 1791 1 thickness of orthe odthe the rings not exceeding ili lil be perceived that the thickness of the rings is incomparably sm smal alier allet ler lei tha thann their breadth from recent observation 11 itis it is believed that the tho rings are not only double but bui that they are separated by poun foun and 4 frome observers ob servera declare le clare claie by b y six 1 I divisions these can oan he ies tie upon shen then thera there inuss 06 axe are an ans perhaps a berm herm in teryl between bethge n each vach r I 1 must te be exceedingly aburn tip appear pears striped mw will dar dax dark kund and bright belts running paralle e with wim its equator these belts ara are broade isi e than those of jupiter but the alter alternation natio of light and ana shade are fess less strongly marked these belts are no doubt produced by I 1 a similar cause to that operating upon jupiter 1 being the results of tha thet great atmos pharic currents arising from the difference dlf dif ferenc of tm temperature in lerent different dlf dif latitudes an and greatly modified in their direction and velocity by the swift rotation of that pla pia planet ep upon its axis 1 the axis of rotation la Is perpendicular til the plane of the rings and also to the belts bem the planet revolves from west td east in a i period of 10 hours 29 minutes and I 1 17 seconds the ring revolves around thi fhi he planet in its own plane in the tho period of or 1 10 hours bours bourdi 32 minutes and 15 seconds weicht almost exactly the same pernod period p 9 as s jhb planets rota rotation tioff there being 0 only n I 1 iwo minutes and seconds 58 difference whether W ege the uhe go several e rings ings revolve in the sarno period h has haa diot riot been determined blobs ervi tion atlon b but ut it is e extremely probable from certain an mechanical m ons founded on tha laws of force lna and ana distance tha that t there therel must bea be a difference in their periods in order that the system may inay be maintained in a stable form of equilibrium n ho W 14 the e rings ring s a are r a prevented hina mina from ge m breaking b difed e t g up p and i n d tailing falling iari vt surface aeb of the planet the IT answer iwen iwer to t this idis as the great cent dent centrifugal r 1 al force lil ill r io rotation tation if ir a moon were p placed e lz at the distance of miles from the centre of saturn it would revolve around the planet in exactly inexactly the same period that the ring now how revolves A satellite then in order to have the same period with the nagi ringi would actually occupy a position in the exterior ring at a distance of 2388 2288 miles from its interior edge egge or miles from its exterior edge the centrifugal force of a satellite in ili the exter lorring lorrin g would be just equal to the centripetal force towards the planet therefore it would have no tendency to fall towards or of recede from the planet nolif we suppose two three ora or a hundred moons situated at the same distance from the ahe planet they would all haya haye the same parne peri period fd and consequently mould would bo be under the same influence of the same two antagonistic force sand would do continue to revolve a atthe bitne same samme distance lfoye lanue if instead of a hundred moons wei we suppose 9 moons joined side by uy side encircling the planet at the sanie same distance froni from its centre subh such a wb uld hivo have no more inore tendency to colla colia collapse i fitall dr fall tail towards the planet than one moon would and further if every moon mool in this va ring tt I 1 instead of being spherical ghoulie bet bei flattened 4 ned out so po a as to form a ring aim alm similar ilir in every eveny respect to the exterior ring dg that thai ta actually surrounds saturn A a ring would revolve in the same pe period iod lod and ac at the e same simel distance as one moon ard nd and would have no disposition to fall towards saturni though it were broken into any number 0 fragments the interior ring if it had the same pei pe i of rd rotation tation as the exterior would have a ten tendency doncy to fall to towards wards the planet fon foe with the same period the centrifugal for force foroe wo would uld be less than the cecii centripetal petal to pre e vent ent ont this tendency to fall the rotation 9 the interior ring must have its velocity in ind ini 4 ceased ci eased in the inverse pro proportion ponti n of th square roots of the distances oto of the tw rings that Is the middle portion of the ini im in i gerior ring id is miles from the centre contre while the distance of the point in the exterior ring at satellite would rev rey revolve olVet inthe in the same time as the miles the square root of the first number is P the tha square root of the second is therefore a point on the middle of the breadth of ot the interior ring ting would ouid edve move miles while the point in ide the the exterior ring moved miles the actual velocity of the nearest point would be miles per second while the actual velocity of the other point would be miles mlle per second if the exterior ring revolves in loh the interior ring should revolve in ah lim ilin nearis nearly ah alm sooner adoner with these vol vel velocities neither of the rings would have bave any tendency to coU collapse apse the quantity of matter towards which the outer ring gravitates is a trifle greater than ther quantity towards which therin nerone gravitates therefore for th ia ta the tha inner inper ring must move a qa egra in ha slower than Woth it otherwise erwi f f e won I 1 alave piave v F not nob made ade the he ne necessary cbs ar Y alf wg 6 arvit arvil la afi thi I 1 r e foregoing calculations eale cale although the tilo great bredt t atilid 0 ca 31 norgo norge boref do 46 r rotation is calculated to ie if r ingal from contracting antil u neu nir they filially coalesce kiec kide el with the stir surface faede faide bf the pla pia planet tiet providing ovidia I 1 that gravity of or the xa rings ng san and ano planet exactly coincide these th se cone cene contres tres fro external s waha whatsoever ts oever become separated by ever so s small in all ali an amount it can be demonstrated that the de del 1 gan Fan ran gement will go on increasing moie more moreane and more until the edge of the ring nearest tot to the centre of the planet will finally come iq contact with its surface an equilibrium of instability is the name given td this kind of mechanical conditions it may mv be exemplified 4 by balancing a rod upon the tip 0 of the finger while the rod stands in an a exact vertical position it maintains itsell itself itsell ina lna in a state of equilibrium and has hag ai no teri terl 4 1 dency to fal fai but this equilibrium la t ble for the slightest deviation froin froia rom h vertical wily wilt constantly be increased antl th the roa rod iod fails falls ana ann the equilibrium Is a dp des troyed there thero is another species ol 01 equilibrium that thit may be called the equilibrium of ifill indof fe ferenee ference retice for instance let iet a brodues aro dUes aspe inda ndoc by ltv its centre of gravity an 0 if I 1 be turned in any position ili id a vertical plane it will have no tendency to rest reit gro I 1 lc Js hits original ginal posit position ign or to increase ita devi atlon but will remain entirely to any change chan 0 J if this rod be like alib and be made madd to legia leyia tt from the verbal it immediately seeks sees t return again to its iid original position as I 1 is manifested by its oscillations on each sia sla of bf its centre contre of gravity this Is an equilia gium of stability all derangements derange ments fran kind bof equilibrium vie vre are not perma delit 1 delther do they roon goon go gol on increasing hut but bu are counteracted by the constant tendency ta W return to the tho primitive condition of equilibrium 14 1 casa case I 1 the rings of saturn were equally thic and homogeneous that ia Is composed of leattor matter of 0 equal density whether they them were wore exactly concentric with the planet br noh not the system would be in a condition of unstable equilibrium equi libri am and therefore would i with the slightest slig hest derangement spee speedily dUT duy destroy itself to construct an equilibrium of stability three things thing are ire necessary first one part art of the ring mastbe thicker or denser than t tri an other parts second the centre of position of the ring must be without the centre of ofa the planet and d third d the the e centre entre of tie tle he ra ring g must a t revolve 1 v around r U d the common cen con tre tte of gravity of the planet and ring in a 4 minute minuty orbit it can be lie analytically demonstrated rated that with these three condi eions the system would be in a state of stable equilibrium eq by observation it is found that mat these conditions do act actually eally Vally exist the ring s actually observed to to be e talc thicker erla erlo an fn some parts than in DA others s it is also actually ab served that the ring is not concentric with the planet and it is further observed that the centre ot the till ring does revolve aroun aronn around d the common cen centre tre of gravity through these causes therefore the system will be maintained through indefinite ages without any danger of 0 permanent arising froin from the slight dei deg deviations lations occasioned by lay thel tha unequal action of or pr by other causes I 1 wen when it known that the interval be tween iween thel the rings does not exceed 1800 isoo mues miles hinr exquisite must be the adjustments to prevent them from collapsing neltha of thel the planer if of equal thickness and dep density sity would alter its relative poi po pol i by i its ts own own mutual gravitations gravitation si bul but one ring ning in the course of a very short time might be precipitated upon the other by the operation of some external for force ce unless prevented by the three conditions which v Q have bave already specified a aap aai necesis feces sary iby to their stability the 0 oj the rp tation odthe of he rings is much greater than thin their orbi lual vel vei veloa citty ay amount the sun gun T the ie cad circum fe deri feri i elpe of t W e oabe othe 4 04 outer r rill rin 14 over miles iti lil there therel ere eret i i behe flave elave aver NA drou 2900 9 mies every hour alil be velocity i y ia I 1 the r around the un 11 only 1 I 01 miles per por ar hour houn our oun during thi topic j h he 0 a absolute p ve velocity oe I 1 y 0 of that point 0 o tho the xing be mos most mosi t distant from the sun resulting from both of these motions will wil I 1 be bo s miles nines per pei hour to toi tbt the east ease east easi while chati point of he the ring near mear i eese fist es the sun will be amov moving I 1 ng woh an absolute ta velocity of ni miles les lei per hour to the west est erom from their noon till their midnight a period perio dof of only about 51 5 hours there must be aa an average eban chan chane change e of absolute blute velocity of about miles per hour the inclination ot of the orbit of saturn to the plane of the ecliptic is equal to 2 deg 29 m s the inclination of the equator and ring to the plane of its orbit is equal to 23 28 deg lim the plane of the ring in the year 1871 1 intersects the plane of the ecliptic in two points namely deg 47 m 8 sj and de 0 eg 47 in 57 ag of longitude the nodes of the ring are ae not quite stationary but advance on the ecliptic about 46 per annum the variety of seasons upon saturn and his hii rings will be somewhat more striking than with us because the inclination of his equator to his orbit is greater than ours summer winter spring and autumn will each be about 7 12 1 2 years long every 15 of our years the sun will apparently pass through the equinoxes equinox es of saturni saturn at which time tima it will be vertical to the outer edge of the ring the sun will apparently recede IQ toi the tile south side of the rings as tar jar ar as ehg tropic or about 39 30 deg S hylt udit at han nan return back again crossing t the d 1 1 or piane Ys beof teof of the ring and con nug nug nue Z 10 aci a deg I 1 north or to the northern t tropic dal I 1 or elwir of b aile be sun suit shines 15 1 years on op the southern side of the rings and then the same same of time on the northern each side ot of tbt the rings therefore has alternately 15 year years da v end and 15 year years night saturn la rih rings tings as are not always visible in th q nt f their relative positions in r regard to tb e sun bun u n lt and nd earth there aie ate thie canses causes joy jom t hei heir ir disappearance fust first we heitne oe itne t 6 sun Is vertical to the |