Youtor
Cepheid Variable Stars IB Physics
>> YOUR LINK HERE: ___ http://youtube.com/watch?v=6F-BIrlZUnA
In this lecture I explain: • What Cepheid variable stars are • The shape of their luminosity time graph and how to find their period using the graph • How the shape of Cepheid variables varies with time, and how the shape affects the luminosity • How Cepheid variable stars are used to measure distance • How to find the luminosity of a Cepheid variable star given its period and vice versa • How to find the distance to a Cepheid variable star given its period and brightness as observed from Earth • Why Cepheid variables are important in the history of astronomy • Henrietta Leavitt's discovery of the relationship between the period of a Cepheid star and its luminosity • Why Cepheid variable stars are in a category of stellar objects called Standard Candles • 0:00 Definition • 0:23 Luminosity vs Time Graphs • 1:35 Astronomy before Cepheids • 3:31 Henrietta Leavitt • 3:52 A problem with measuring distance in space • 5:23 Leavitt's idea • 6:34 The Magellanic Clouds • 7:30 Luminosity vs. Period graphs • 10:50 Finding distance to Cepheids • 12:45 Example Problem • 14:14 Standard Candles
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