OUTBREAK IN SUN.

Auckland Star, Volume LXIV, Issue 117, 20 May 1933, Page 9 (Supplement)

OUTBREAK IN SUN.

WHAT ARE SUNSPOTS?

prolonged study.

EFFECT ON WEATHER.

(By F.H.A.S.)

After a period of comparative calm, the eun recently developed a state of disturbance which manifests in a aenee of spot groups of considerable magnitude. Seen in a pair of binoculars (cautiously screened from the dangerous glare and heat produced by unprotected lenses) they presented the appearance of lengthened gashes forming a sort of procession; while the telescope revealed many smaller spots. There are also scores of "pinholes" a thousand miles or less in width. A rough measure of the largest of these groups taken at the time showed it to be from 290,000 to 310,000 miles long, while the diameter was rather more than 85,000 miles. These spots having been carried Tound to the side of the sun turned away from the earth—borne thither, that is to say, by the solar rotation, become lost to sight. Here they may die down and finally disappear altogether, or persist adn reappear in due course on the pastern edge of the sun, once more to cross liia face. Rotation ol Sun. It is the movements of sunspots more than anything else that has proved the fact that the sun, like the earth, turns continually upon its The sun revolves on an axis which is nearly at right angles to the plane of the earth's orbit iu a period of about 25 days, the spots near the equator travelling faster than the general axial whirl of the sun. It should, however, be stated that the period of rotation as indicated by the motion of the spots is not the same for all portions of the solar surface. "While spots at the equator rotate in sbout 25 days, those situated between 20 and 30 degrees of the sun's equatorial latitude require 20, and those which ■belong to a zon\ 40 degrees from the

equator require 27 days to perform a revolution. Those parts of the sun s surface situated within 15 degrees of the poles require 30 days for a revolution. All this goes to prove that our "light by day" is not a solid body. The same condition of things obtains in the yet hot and plastic planet Jupiter, which is just now so conspicuous an object in our late evening and early morning skies. Tho average speed with which sunspots move is a little more than SO miles a minute.

In connection with the recent groups there were to be seen the usual accompanying display of faculae, consisting of bright elevated streams surrounding the groups of spots and extending some distance beyond. They are believed to be the 'ops of clouds of vapour rising from the sun, and are probably connected with the tremendous red flames or "prominences" which leap up from its surface to a height of many thousands of miles. The faculae are the more brilliant parts of the sun; and when in the neighbourhood of a spot, it is not difficult, even with a email telescope, to detect their diversified forma, having quite distinct outlines, and either separate or uniting in various traceries into ridges aud network. They may be of varied extent, from almost indiscernible, soft-gleaming strips 1000 miles long, to enormous ridges more than 40,000 miles in length, and from 1000 to 4000 miles broad. Faculic markings may be seen all over the sun's surface, but are more abundant in the vicinity of a spot or spot-group. The penumbra surrounding or enclosing the darker umbra appears like a steep cliff sloping downwards qn to it. This is a general characteristic of solar spots, the sloping penumbrac being sometimes more than 2000 miles deep. Connection With Weather. Sunspots are found to be a most fascinating study in small as well as large telescopes. But notwithstanding the prolonged and minute attention which has been devoted to them for many years past by experts, their exact nature is still very largely a matter of mystery. Even the refined and ingenious processes which are now employed in their examination are incompetent to so analyse them as to extract their secret. It is evident, however, that they are openings in the photosphere, or luminous envelope of the sun, from which the bright doudets have been temporarily removed, exposing the comparatively dark interior. The writer has sometimes witnessed the inner edges of a spot as it was inciting and falling in. By means of spectro heliograph pic-

tures one may see how the masses of hydrogen and calcium vapours whicli lie above and around them are whirled in vortices. But whether a sunspot represents an uprusli of heated matter from within or a downrush of cooled gas from above still remains uncertain. In any case sunspots are taken generally as indicating an activity which is not merely superficial, but which affects the structure and functions of the sun. Sunstorms (for such the spots really are) are not usually felt by us to any appreciable extent until they reach tho middle regions of the sun's disc. On passing that phase they sometimes give rise to sympathetic electrical and magnetic disturbances on the earth. Only in a general sense can it be claimed that the sun determines the weather upon tho earth. If one may so put it, sunweather affects arid in some degree determines world weather. So many local circumstances and conditions modify the direct influence of the sun —circumstances and conditions which overlap and interchange and moderate or intensify each other —that it will probably be a long time ere ecience will have advanced to such a stage as to render it possible to disentangle and estimate these interpenetrating and conflicting forces and fortell what weather conditions will prevail in any district, country or area.

The whole question of sunspots is highly complicated, and astronomers, feeling that much is involved in a solution of it, are not slack in their attention to the subject. For a number of years past there has been an organisation at work in several observatories in England and elsewhere by which the sun has been photographed every day. Weather being unfavourable in one place, it is sure to bo suitable in another; and thus long and continuous observation is now practicable, and nothing is missed. While the number and area of sunspots are being faithfully recorded for study and reference, new methods are continually being devised specially for this class of work.