This is the first of two videos about binary stars and their applications. We learn that there are many types of binary stars, and some of the most important are very near to us. This is part of my complete intro Astronomy class that I taught at Willam Paterson University and CUNY Hunter. Alcor and Mizar: Nu Draconis: Albireo: Sirius: Hubble Space Telescope Measurement of Sirius B's Mass: Sky Safari: Washington Double Star Database: Newton's form of Kepler's 3rd law: On a Revision of Certain Spectroscopic-Binary Orbits, by R. F. Griffin: Binary Stars in General: Stellar Masses: 0:00 Introduction 0:01 Apparent Binary Stars 2:31 True Binary Stars 4:28 True Binaries are gravitationally bound. 5:14 Types of True Binaries 6:40 The motion of the star Sirius across the sky 11:52 Measuring Masses 12:49 Why are Visual Binaries so Important? 13:40 Visual Binaries and Masses 14:58 Measuring the Masses of the Stars 16:25 Sirius "B" Mass Measured... 17:55 Spectroscopic Binaries 19:49 Spectroscopic Binary Real Data.