Binary stars are some of the most important stars to study, as they are the gateway to astrophysics. We can determine their masses and we can determine many other things about them. So, here we chat more about spectroscopic and eclipsing binaries, and how a planet about the size of Earth was found orbiting the star nearest to the Sun. This is part of my complete intro Astronomy class that I taught at Willam Paterson University and CUNY Hunter. Algol On a Revision of Certain Spectroscopic-Binary Orbits, by R. F. Griffin Binary Stars in General Stellar Masses The sky around Alpha Centauri and Proxima Centauri (annotated) The motion of Proxima Centauri in 2016, revealing the fingerprints of a planet SuperWASP Observations of Variable Stars Algol at AAVSO Main-Sequence Effective Temperatures from a Revised Mass-Luminosity Relation Based on Accurate Properties The location of Proxima Centauri in the southern skies Proxima Centauri and its planet compared to the Solar System Artist's impression of the planet orbiting Proxima Centauri Pale Red Dot: A search for Earth-like planets around Proxima Centauri Powerful Flare from Star Proxima Centauri Detected with ALMA; puts habitability of nearby system into question 0:00 Introduction 0:01 Spectroscopic Binaries 1:18 Spectroscopic Binary Real Data 4:17 Proxima Centauri Doppler Shift due to a Planet! 6:31 Eclipsing Binaries 11:55 Eclipsing Binary: Algol, Beta Perseus 15:24 Stellar Masses from Close Binary Stars 24:07 The Doppler Effect.