An Introduction to the Study of Variable StarsHoughton Mifflin, 1915 - 327 pages |
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Common terms and phrases
Algol angle Annals aperture appear Argelander Argelander's artificial star astronomers beam binary bright bands bright star brighter called catalogue cell Cephei Ceti chapter charts Class color column comparison stars constellation contains crystal declination described determined difference in magnitude Durchmusterung epoch equal error faint stars fainter focal give given Hagen Harvard College Observatory Harvard Observatory hence hydrogen lines instrument intensity interval investigation Julian Day length light step long period variables Lyrae maps maximum mean light curve measured method Nicol nitudes Nova observations obtained orbit phase photometric Pickering placed polarized position prism published radial velocity rays right ascension scale Schönfeld selenium short period variables spectral type spectroscopic spectroscopic binaries spectrum star image stellar magnitude stellar spectra taken telescope tion Uranometria vari variable stars variation velocity visual wave-length Yerkes Observatory zone
Popular passages
Page 218 - I was looking — namely, to extend his novel methods of research upon the sun to the other heavenly bodies. A feeling as of inspiration seized me : I felt as if I had it now in my power to lift a veil which had never before been lifted ; as if a key had been put into my hands which would unlock a door which had been regarded as for ever closed to man — the veil and door behind which lay the unknown mystery of the true nature of the heavenly bodies.
Page 137 - Photographs of Stars of unequal brightness present marked peculiarities in size and intensity, when their images formed in equal exposures are compared together, at once suggesting the possibility of classifying them according to a scale of photographic or chemical magnitudes, analogous to the common optical scale, but differing from it essentially, in the fact of its being based upon actual measurements, in place of the vague and uncertain estimates to which astronomers have hitherto resorted in...
Page 228 - If it were not perhaps too early to hazard even a conjecture on the cause of this variation, I should imagine it could hardly be accounted for otherwise than, either by the interposition of a large body revolving around Algol, or some kind of motion of its own, by which part of its body covered with spots or such like matter, is periodically turned towards the earth.
Page 111 - ... the ratio between the sine of the angle of incidence and the sine of the angle of refraction is a constant, depending only upon the nature of the two media.
Page 218 - This news was to me like the coming upon a spring of water in a dry and thirsty land. Here at last presented itself the very order of work for which in an indefinite way I was looking — namely, to extend his novel methods of research upon the sun to the other heavenly bodies.
Page 258 - Therefore do I lay these hitherto sorely neglected variables most pressingly on the heart of all lovers of the starry heavens. May you become so grateful for the pleasure which has so often rewarded your looking upward, which has constantly been offered you anew, that you will contribute your little mite towards the more exact knowledge of these stars! May you increase your enjoyment by combining the useful and the pleasant, while you perform an important part towards the increase of human knowledge...
Page 293 - ... thus giving a map on the standard scale of one minute of arc to one millimeter. The stars on these maps, while appearing coarse by daylight, are thus easily seen and identified at night without using a light bright enough to dazzle the eye. The designations of the stars in the sequence are marked upon these enlargements, and copies will be furnished at cost. Charts will be furnished free of cost to experienced observers who are ready to cooperate in the above plan of work. Observations of nearly...
Page 218 - I soon became a little dissatisfied with the routine character of ordinary astronomical work, and in a vague way sought about in my mind for the possibility of research upon the heavens in a new direction or by new methods.
Page 278 - 365 3, and o Ceti were given as examples. In the last of these stars the hydrogen lines are bright, and this spectrum has been shown to be characteristic of variable stars of long period; indeed, by this peculiarity in the spectrum about a hundred new variables have been found. A further examination of these spectra shows that they can be further subdivided into eleven groups. A classification was made from an examination of the continuous spectrum, the comparative brightness of the hydrogen lines...
Page 271 - ... most earnest efforts from the beginning of his career were directed. In one of his letters to Von Humboldt, in 1850, after speaking of the dependent condition at that time of science in 'America, its self-distrust and intellectual timidity, he'says : " This I knew before returning home, but realise it now, for the first time, to its full extent. Therefore it is that I dedicate my whole efforts, not to the attainment of any reputation for myself, but to serving to the utmost of my ability the...