. The Adolfo Stahl lectures in astronomy, delivered in San Francisco, California, in 1916-17 and 1917-18, under the auspices of the Astronomical Society of the Pacific. Fig. 1—In Orion (5^ ^:—2° 27).. Fig. 2—In Sagittarius (17^ ;—27° 50). PLATE XLV. Dark by H. D. Curtis, Crossley Reflector. News from the Stars 169 brightness lasts for a few days or hours only and is followedby a more or less gradual decline which often proceeds to thepoint of absolute invisibility: and the various stages of itslight curve are synchronal with well defined changes in thespectrum. Aari
. The Adolfo Stahl lectures in astronomy, delivered in San Francisco, California, in 1916-17 and 1917-18, under the auspices of the Astronomical Society of the Pacific. Fig. 1—In Orion (5^ ^:—2° 27).. Fig. 2—In Sagittarius (17^ ;—27° 50). PLATE XLV. Dark by H. D. Curtis, Crossley Reflector. News from the Stars 169 brightness lasts for a few days or hours only and is followedby a more or less gradual decline which often proceeds to thepoint of absolute invisibility: and the various stages of itslight curve are synchronal with well defined changes in thespectrum. Aarious explanations of these phenomena havebeen offered. Certainly a nova is the result of a celestialcatastrophe of some kind, but no completely satisfactoryexplanation of the nature of the catastrophe has so far beenfound. The most plausible theory (though one not entirelyfree from objections) is that the outer strata of a dark ornearly dark star rushing through a region of space filled wnthmore or less dense nebulosity are heated to incandescence, thedepth of the incandescent strata and the intensity of the con-sequent luminosity depending upon the degree of resistanceencountered by the star.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectastronomy, bookyear19
