The SunD. Appleton, 1911 - 447 pages |
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Common terms and phrases
absorption angle Ångström appear atmosphere beam bolometer bright lines calcium calories carbon Chapter chemical elements chromosphere clouds corona curve dark lines diameter displacement distance earth earth's atmosphere eclipse effect elements emission emit energy eruptive faculæ flash spectrum Fraunhofer lines gaseous gases glass grating gravitation heat helium Hence hydrogen indicate infra-red intensity kilometers latitudes less magnetic mass maximum mean measured method miles minor planets mirror moon motion Mount Wilson nearly observations Observatory orbit perfect radiator period photographic photosphere planets plate polarization pressure prism produce prominences protuberances pyrheliometer radius ratio rays reversing layer Rowland's seen shown slit solar constant solar image solar lines solar radiation solar rotation solar spectrum solar system spec spectra spectral type spectroheliograph spectroscope spectrum lines spots stars stellar sun-spot sun's disk sun's limb telescope temperature tion trum ultra-violet vapor velocity of light violet wave lengths
Popular passages
Page 4 - II. The radius vector of each planet describes equal areas in equal times. III. The squares of the periods of the planets, are proportional to the cubes of their mean distances from the sun; ie, ti :t 3 *:: a* : a/. This is the so-called
Page 196 - There is no regular process for the formation of a spot. Sometimes it is gradual, requiring days or even weeks for its full development, and sometimes a single day suffices. Generally, for some time before the appearance of the spot, there is an evident disturbance of the solar surface, manifested especially by the presence of numerous and brilliant faculse, among which, " pores " or minute black dots are scattered.
Page 149 - When the spectroscope is used as a means of rendering visible the forms and features of the prominences, the. only difference is that the slit is more or less widened. The telescope is directed so that the solar image shall fall with that portion of its limb which is to be examined just tangent to the opened slit, as in Fig.
Page 164 - Our figures present some of the more common and typical forms, and illustrate their rapidity of change, but there is no end to the number of curious and interesting appearances which they exhibit under varying circumstances. The velocity of the motions often exceeds a hundred miles a second, and sometimes, though very rarely, reaches two hundred miles. That we have to do with actual motions, and not with mere change of place of a luminous form, is rendered certain by the fact that the lines of the...
Page 217 - Immediately above this lies the so.called " reversing stratum," in which the Fraunhofer lines originate. It is to be noted, however, that the gases which compose this stratum do not merely overlie the photosphere, but they also fill the interspaces between the photospheric clouds, forming the atmosphere in which they float, and an attempt has been made to indicate this fact in the diagram. Above the " reversing stratum " lies the scarlet chromosphere, with prominences of various forms and dimensions...
Page 198 - The average life of a sun.spot may be taken as two or three months ; the longest yet on record is that of a spot observed in 1840 and 1841, which lasted eighteen months. There are cases, however, where the disappearance of a spot is very soon followed by the appearance of another at the same point, and sometimes this alternate disappearance and reappearance is several times repeated.
Page 48 - It may also be defined as the sine of the angle of incidence divided by the sine of the angle of refraction, as light passes from air into the substance.
Page 423 - Schuster-)- has also made and developed the interesting suggestion that a massive star would arrive sooner at the solar stage because its greater surface attraction would enable it to absorb...
Page 196 - pores," some of them, coalesce with the principal spot, some disappear, and others constitute the attendant train. When the spot is once completely formed, it assumes usually an approximately circular form, and remains without striking change until its dissolution. As its end approaches, the. surrounding photosphere seems to crowd in upon and cover and overwhelm the penumbra. Bridges of light, often many times brighter than the average of the solar surface, push across the umbra, the arrangement...
Page 431 - The phenomenon of the increase of velocity with the evolutional stage of the stars must give rise to speculation as to its cause. The observational results contained in our table naturally lead us to conclude that the matter from which the stars originate must have little or no velocity. How is this possible under the influence of the combined attraction of the rest of the system ? Is it not as if gravitation had no effect on the cosmical matter in its primordial state?