NATS 1740 Lecture Notes - Inverse-Square Law, Binary Star, Apparent Magnitude

• School: York University
• Department: Natural Science
• Course: NATS 1740
• Professor: Randy Hoffman

Document Summary

2 similar looking stars can be generating very different amounts of light. Apparent brightness: how bright stars look in our sky (amount of power reaching us per unit area) Luminosity: the total amount of power that a star emits into space. A stars apparent brightness in the sky depends on both its true light output or luminosity and its distance from us. The apparent brightness of a star or any other light source obeys an inverse square law. Doubling the distance to a star would decrease is apparent brightness by a factor of 2 or. Inverse square law: apparent brightness = luminosity/ 4 x (distance)2. We can measure the distance to a nearby star by observing how its apparent location shifts as earth orbits the sun. Stars parallax angle is smaller the further away it is. Stars come in a wide range of luminosities with our sun sometwhere in the middle. Dim stars are far more common than bright stars.