ASTRONOMICAL NOTES FOR MAY.

Press, Volume LXIV, Issue 13103, 30 April 1908, Page 6

ASTRONOMICAL NOTES FOR MAY.

(By tite Rev. P. W. Faibcxoitgh, F.R.A.S.) Tho mm's dastamoo on May Ist is £3.642,000 mflcs. an incrcaeo of 2,300,000 imilrs sine© January Ist. Venus is a splendid evening star. Sim -ivi.il bo four degrees north, of the moon on. the 4th, and at her greatest brilliancy on tho 29tih. Juipitor, second only to V«n us in lustre,, is seen in t"no noKtJvweet. He is in tho constellation of Cancer, and will bo in conjunction withi tlw> moon on tlna 7th. iM.i.rs is still an evening fitar, but low down, and will be about .throe degrees north of tho moon on tho 3rd. Of tho constellations, Taurus sets early, Aldebaran ibc-jing still visible dn tho twilight. Onion is ia lilbtle later. Gomini is aiko low. Tx-o, otherwise tho sickle, is well up in tho west. To th« north-east of Leo is Bean tlw> spleur did rod st«ac\ Arcturus., to whoso magnitude and swift motion wo have often referred. In the oast Scorpio stretched out its groat length. No other ancient ccnst«JJa.ticrJi is co Tike the creatuTo from winch it derives its name. Tho red star, Antares, is an its back. Tho claws spread northward, and the long tail, curving up and tJnen curving down, lies to the south. Antares derives its truuno fToni tine fact that it is like Mare, and was often mistaken for the .planet b> - tho inexpert. The name is made up of tho Greek anii, in place of, a<nd Ares, Mans. In our discussion of tho sun last month -we saiid nothing of tho most widely known solar phenomena—sun spots. We ha>vo described tho vaxioue eolar onmblojpos, which are—(l) the photosphere, or lighit shell 3 tho inner*mosfc; (2) the layer of genteral absorption; (3) 'the reversing layer; (4) tho chromosphere and prominences, and (5) the ipea-rfy corona. Tho epots seem tc be .imbedded i-n the photosphere. Whether they aje depressions ox elevations is still disputed. They -were long reasuded as rents, or craters, through vrhjoh titeuric volcanic energy 'had burst ke way. There is now a. growing tendency to regard them as regions where cooled gases fall back to the solar turnaoo. Others (regaaxl tkeviu an eolar tycionee.

Spats vary in magnitude from mere telescopic specks to enormous blotches covering an area of more than a -thousand million square miles, and eaaily visible to the- .naked eye. A spot "in 1892 was 150,000 miles long, with a maximum width of hatf ita length. The spots change in size and form, sometimes rapidly and sometimes slowly. A 6pot that appears id a violent paroxysm is accompanied by iragneitio disturbances , and often by auroral displays, but- one that appears quietly has no sucth effect. Tho great spot of 1892 lasted through five revolutions of tho sun, or about 125 days. One spot has boecn. known to enduro throuigh eighteen revolutions,, or 450 days. Tho average life of a spot is a-bout 50 days.

It waa by observing spots that the rotation of tlio sun on its axis was first discovered. Continued observation has. shown that the solar rotation is ono of tihe most complicated problems known to science. There aTe not only different periods of rotation for dif-fo-ront latitudes, as in Jupiter, but different periods for different altitudes. The rotation has been determined from observing; (1) fac-ulre or bright scales; (2) spots; (3) by the spectroscope. The results are lor the equator 2-I.UG days, 25.09 days and 25.46 dttys respectively. For latitude 15 north or south, 25.26 days, 25.U days and 20.35 days. For ktitud-e 30, 25.-18 days, 2U.53 days and 27.57 days. A spot in latitude 50 gave 27.5 days and tho spectroscope, finds in latitude 80 a rotation in 38.5 days!

All the linos of enquiry agreo that the rotation is most rapid at the equator and that it diminishes rapidly toward t'foc poles. The finding of tho spectroscope re luiiformly longer than the period determined by faculse suwl spots, wliich indicates tltat tho instrument is dealing with eomo retarded source* of light. iStill more curious is the fact that tho speed of rotation varies with tho elevation, ■Iμit not consistently. Tho reversing layer is higher then the photosphere, tlie. home of tho spots, and rotates more slowly. The. faculso aro associated with tho photosphere and aro higher than the spots, but rotate faster than, tho spots! Tho drift of ono over the other is al"waye para-110l to tho equator, and not aslr.'n.t, like our trade winds. It has been suggested that this confusion of rotation is a &nnvivtill of jKibuJar oomditiians. , Tho faoiila, or bright scaie-1 ike clouds, and the flaming prominences, are both most frequent in tho spot regions. There is some mysterious bond between these thro© phenomena. The periodicity of sjwts was first discovered by Schwa-be in 1851."The average <jyc4o is about eleven years, but there aro gireat fluctuations. Tino cycle has bcian as ehort as seven years arid three months, and ac long as sixteen years. There aro aJso long flolsur caJ-tns, in which the spot maxima aro feeble- amd submerged. In. the seventeenth, contrary £ho raiaxima of ICGO, '71, '84, '95, and 1705 were re-presented by sdnglo spots. From 1575 »to 170 C no ewucTia wes observed an England. Tho normal maximM-m. of spate returned in 171 G. Tho fspot rycies aleo overlap one another, so that ono cycle hae adI vanced a year er two before the pro-v-Doais ono has ended. If this bo taken itnto account tho cycles are tih&rtw.n or fourteen yeoirs long. New cycles invsurdably Ix-gin "by the a-ppeaT-nnc© of spots from 30d>eg. to 35deg. worth, and south. Spots- aro mured y seen Purtiher ifroan. tilio equator than ili-is. As tho cycle- eidvamoes tine epo&e appear and ineaaiear to the <«qi\ator. Tlio Tnasim,tnm ocoitrs about 16deg. on either side of fUie equator, and as tlie cycle diios away the last Ebragg&Lng apote are nearer etaSl to tihio "line." Hie-nco dt as easy to ddstinguish kotweem the so?ots Wonting to tho old and the now cycles. The old consists of a ling of spots on each 6ide of the equator, and close to it, 'Trhirle tho new cydo consists of two other Tingß from 30deg. to 35deg. nortih and eoiitti. On the whole, the facts seem to suggest that sprats hxeve their origin from tho anterior of tho sun ratshea* than from witihonit. But Opipolzer, of Vieinn-a, lhas Buggiceted' thart they are due to bodies of gas irieing from the polar regions of tho sun drifting to■wa.rds the equatoTj and , descending in successive epot aones, as- an tho caso of desmnding cujremt& of cold air an tlixpi eartihi's «;hnosphere. Tttiiat tJiero is a reLaition bobwoon sum- spots a.nd teirestrial magnetism- ie we! 3 esta-blishod. Often, bu* not always, solar disfcurbanoos ooincade with "magne-toc etonns" on ea-nthj and •wiih briiliant euiYwas. But dt as not kno"w'n whether the sclia-r disturbance ca-uses tlnat on th<e earth, or whether bo'tih aro duo to somo oxtornal anfluoiioe. it is atoo -believed tlhast the v>ar-in,t'ian of longitude on earth is oonwith sun spots, and that oamete thait visit ih<a sun at the maximum period are i/rig-hiter than tihose that come at ntrininiumi. Tho effect of spots on the weather and the rainfall is a question still under discussion.