AST-1A Chapter Notes - Chapter 12: Light Curve, Orbital Period, Absolute Magnitude
Document Summary
Brightness of a star depends on its distance as well as how much light it actually emits. Apparent brightness: the amount of power reaching us per unit area. Inverse square law for light: luminosity: the total amount of power that a star emits into space surrounding the star. With distance describes the force of gravity. The same total amount of light must pass through each imaginary sphere. Amount of light received per unit area decreased with increasing distance by the. Apparent brightness = luminosity/ 4(pie) x distance^2 square of the distance. Most direct way of measuring a stars distance. Compare observations of a nearby star made 6 months apart. We can calculate a stars distance if we know the precise amount of the stars annual shift due to parallax and its parallax angle. Smaller if the star is further away. These measurements are key to all other distance measurements in the universe.
