CONTENTS[LECTURE I. THE INTERIOR OF A STAR][9][Temperature in the Interior][11][Ionization of Atoms][17][Radiation Pressure and Mass][24][The Interior of a Star][26][Opacity of Stellar Matter][28][The Relation of Brightness to Mass][31][Dense Stars][36][LECTURE II. SOME RECENT INVESTIGATIONS][42][The Story of Algol][42][The Story of the Companion of Sirius][48][Unknown Atoms and Interpretation of Spectra][53][Spectral Series][59][The Cloud in Space][63][The Sun’s Chromosphere][70][The Story of Betelgeuse][76][LECTURE III. THE AGE OF THE STARS][85][Pulsating Stars][85][The Cepheid as a ‘Standard Candle’][90][The Contraction Hypothesis][94][Subatomic Energy][99][Evolution of the Stars][106][Radiation of Mass][113][APPENDIX][Further Remarks on the Companion of Sirius][122]