AST201H1 Chapter Notes - Chapter 15: Inverse-Square Law, Dim Stars, Apparent Magnitude
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AST201H1 Full Course Notes
All stars form in great clouds of gas/dust, and each begins its life with roughly the same chemical composition as the sun: h, he, and. Stars differ in size, age, brightness, and temperature. Fundamental properties of stars: luminosity, surface temperature, mass. The brightness of a star depends on its distance as well as on how much light it actually emits: why we can"t simply look up at the sky and say one star is brighter than another. Apparent brightness: the brightness of a star as it appears to our eyes: defined as the amount of power (energy/s) reaching us per unit area. Luminosity: the total amount of power (energy/s) that a star emits into space. The same light is diffused over a larger area. Inverse square law for light: law stating that an object"s apparent brightness depends on its actual luminosity and the inverse square of its distance from the observer. o.