NATS 1740 Lecture Notes - Lecture 4: Apparent Magnitude

• School: York University
• Department: Natural Science
• Course: NATS 1740
• Professor: Michael De Robertis, Alireza Rafiee

Document Summary

Have a camera to measure the luminosities, and to know how far is the star. As the star gets bigger and bigger, the star gets less energy. The further the star, the more it looks fainter. Brightness of star is what you can really measure. Brightness of a star depends on both distance and luminosity. Some looks really bright and some look faint (not because it"s small, but it"s far away) You can"t tell exactly which stars are brighter unless you know the distance. Luminosity: amount of power a star radiates (energy per second = watts) Apparent brightness (what you measure on the ground): amount of starlight that reaches earth (energy per second per square). The energy is conserves, luminosity passing through each sphere is the same. Area of sphere: 4 (radius)^2, divide luminosity by area to get brightness. The relationship between apparent brightness and luminosity depends on distance.