CELESTIAL MAGNETS.

Oamaru Mail, Volume XVIII, Issue 12070, 25 October 1913, Page 3 (Supplement)

CELESTIAL MAGNETS.

That the earth is a great magnet lias long been known. That the sun is one also now appears very probable. It can not, however, be a permanently magnetized body, lor such bodies loso their magnetism at temperatures far below that of the solar mass. The interesting theory that every largo., rotating body is a magnet was advanced

in 1891, and if this is so, it would make not only earth and sun, but also every celestial body, a magnetic, globe. So far, however, this is only an improved, though very interesting, hypothesis. With regard to the sun it 'has now been.definitely shown that the, vortices known as sain spots, are magnetic, owing, to' the fact that electrified particles are carried around in their whirls. They are: electro-magnets, the electrified vortex acting in this respect precisely like the spiral electric current around the core of' an ordinary telegraph' or bell magnet. The discovery of theso local solar magnetic phenomena is duo to the previous discovery that a magnetic field, splits the lines in the spectrum of light traversing the field. Professor George E. Hale, of the- Mount Wilson Solar Observatory in, California, first observed this splitting in certain lines of tlie solar spectrum and attributed it to'its true cause. In'Tho Popular Scienco Monthly (Now York) Professor Hale describes efforts to apply the same line of reasoning to tho .sun .as a whole, which he thinks ha\'.e established the magnetic character of that body. Ho writes:

The structure of the corona, as revealed at total eclipses, points strongly in this direction. . . . Bigelow, in 1889, investigated this coronal struc r ture, and showed that it is very similar to the lines of force of a spherical magnet. Stormer, guided by his own - researches on the aurora; has calculated the trajectories of electrons moving out from the sun under the influence of a general magnetic field, and compared l these trajectories with the coronal streamers'". Tho resemblance is, apparently too close to the result, of chance. Finally, Desla*ndres has, investigaio'di the forms and motions of"solar prominences, which he finds to behave as they would in a magnetic field of intensity about one millionth that of the earth. We may thus infer the existence, ql;" a general solar magnetic field. But since the sign of the charge of the outflowing electrons is not certainly known, we can not determine the polarity or the sun" in this way. ... . . . ' . To . . . . detect the magnetic field of the sun as distinguished from that of the sun's atmosphere, wo must resort to the method employed in tho case of the sun-spots: .... If this is successful, h will not only show beyond doubt whether the sun is a magnet: it will also permit the polarity of the sun to be compared with that of the earth, give a measuro of the strength of the field! at different latitudes, and indicate the sign of the 'charge that a rotating sphere must possess if it is to produco a similarfield. ....

"I shall not trouble you with the deA tails of the hundreds of photographs and the thousands of measures which have, been made by my colleagues and myself during the past. year. In view of the diffuse character of tho solar lines unrier such high dispersion, and tho exceedingly .small displacements observed, the results must bo given with some, nerve. Though they appear to leave no doubt as to the reality of tho effect "It must remain for the future to confirm or to overthrow the apparently strong evidence in favor of the 'existence of a true Zeernan effect, due. to the general magnetic field of the sun. If this evidence can be accepted, we. may draw certain conclusions of present interest.

Taking the measure at their face value, they indicate that tho north magnetic pole of the sun lies at- or near the north pole of rotation, whife the south magnetic pole lies at or near tho touch pale of rotation... In other words, if a compass-needle could withstand the solar temperature, it would point approximately as it does on the earth, since the polarity of the two bodies appears to be the same. . . . . "In This survey of magnetic phenomena, we havo kcut constantly in mind the hyopthesis that the magnetism of the earth is due to its rotation. Permanent magnets, formerly supposed to account for the earth's magnetic field, could not exist at. the high temperature of the sun. Displays of the aurora, usually accompanied by magnetic storms, are plausibly attributed to electrons reaching the earth from ilio sun, and illuminating the rare gases of the. upper atmosphere just as they affect those in a vaciuiin-tube. Definite proof ; of the existence of free electrons in the sun is afforded by tho discovery /of powerful local magnetic fields in suiHspcts, where the magnetic intensity is sometimes as great as 1 nine, thousand times that of the earth's field. These local fields probably result frbm. the rapid revolution in a vortex of . negative electrons, flowing toward tho cooler spot from the hotter regioii outside. The sanio method" of observation now indicates that the.'whole sun is a magnet, of the same polarity of; the earth. Because of the : high' solar temperature, this magnetism ..may. '"bd ; ascribed to the sun's axial rotation. It; is not 'improbable that'the .eafthSmate netism also "results from ■rotation; aij'd that other rotating celestial' bodies, such as stars and" neb'u Ih>,' may. ultimately 'be'. found, to possess magnetic properties. Thus, while 'the' presence of. free elejtrons in the sun prevents oui' aceoptance of the' evidence' as '.'a proof - that every large rotating"''"body'is-a magnSt';the results of the 'investigation are" -np,t;' opposed "to "this hypothesis, which" maybe tested further by : 'the' study of tither stars of known diameter and-velocity :ol rotation." ' :