This is an audio version of the Wikipedia Article: https://en.wikipedia.org/wiki/Binary_star 00:02:55 1 Discovery 00:06:36 2 Classifications 00:06:45 2.1 Methods of observation 00:07:26 2.1.1 Visual binaries 00:09:22 2.1.2 Spectroscopic binaries 00:12:42 2.1.3 Eclipsing binaries 00:15:26 2.1.4 Non-eclipsing binaries that can be detected through photometry 00:16:11 2.1.5 Astrometric binaries 00:18:25 2.2 Configuration of the system 00:19:48 2.3 Cataclysmic variables and X-ray binaries 00:21:25 3 Orbital period 00:21:48 3.1 Variations in period 00:22:58 4 Designations 00:23:08 4.1 A and B 00:24:00 4.2 Discoverer designations 00:24:30 4.3 Hot and cold 00:26:33 5 Evolution 00:26:42 5.1 Formation 00:27:49 5.2 Mass transfer and accretion 00:29:48 5.3 Runaways and novae 00:31:31 6 Astrophysics 00:32:41 6.1 Calculating the center of mass in binary stars 00:34:06 6.2 Center of mass animations 00:34:21 6.3 Research findings 00:34:31 6.3.1 Planets 00:34:42 7 Examples 00:37:22 8 Multiple star examples 00:40:08 9 See also 00:43:07 10 Notes and references 00:44:55 11 External links 00:45:04 Notes and references 00:45:14 External links Listening is a more natural way of learning, when compared to reading. Written language only began at around 3200 BC, but spoken language has existed long ago. Learning by listening is a great way to: - increases imagination and understanding - improves your listening skills - improves your own spoken accent - learn while on the move - reduce eye strain Now learn the vast amount of general knowledge available on Wikipedia through audio (audio article). You could even learn subconsciously by playing the audio while you are sleeping! If you are planning to listen a lot, you could try using a bone conduction headphone, or a standard speaker instead of an earphone. Listen on Google Assistant through Extra Audio: https://assistant.google.com/services/invoke/uid/0000001a130b3f91 Other Wikipedia audio articles at: https://www.youtube.com/results?search_query=wikipedia+tts Upload your own Wikipedia articles through: https://github.com/nodef/wikipedia-tts Speaking Rate: 0.9306662182569719 Voice name: en-US-Wavenet-E "I cannot teach anybody anything, I can only make them think." - Socrates SUMMARY ======= A binary star is a star system consisting of two stars orbiting around their common barycenter. Systems of two or more stars are called multiple star systems. These systems, especially when more distant, often appear to the unaided eye as a single point of light, and are then revealed as multiple by other means. Research over the last two centuries suggests that half or more of visible stars are part of multiple star systems.The term double star is often used synonymously with binary star; however, double star can also mean optical double star. Optical doubles are so called because the two stars appear close together in the sky as seen from the Earth; they are almost on the same line of sight. Nevertheless, their "doubleness" depends only on this optical effect; the stars themselves are distant from one another and share no physical connection. A double star can be revealed as optical by means of differences in their parallax measurements, proper motions, or radial velocities. Most known double stars have not been studied adequately to determine whether they are optical doubles or doubles physically bound through gravitation into a multiple star system. Binary star systems are very important in astrophysics because calculations of their orbits allow the masses of their component stars to be directly determined, which in turn allows other stellar parameters, such as radius and density, to be indirectly estimated. This also determines an empirical mass-luminosity relationship (MLR) from which the masses of single stars can be estimated. Binary stars are often detected optically, in which case they are called visual binaries. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (spectroscopic binaries) or astrometry (astrometric binaries). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called eclipsing binaries, or, as they are detected by their changes in brightness during eclipses and transits, photometric binaries. If components in binary star systems are close enough they can gravitationally distort their mutual outer stellar atmospheres. In some cases, these close binary systems can exchange mass, which may bring their evolution to stages that single stars cannot attain. Examples of binaries are Sirius, and Cygnus X-1 (Cygnus X-1 being a well-known black hole). Binary stars are also common as the nuclei of many planetary nebulae, and are the progenitors of both novae and type Ia supernovae.

• published: 20 Mar 2019
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