ASTRO 102 Study Guide - Sun-1, Thermal Radiation, Orbital Period
Document Summary
Luminosity: amount of power a star radiates: energy per second = watts, apparent brightness (or flux): amount of starlight that reaches earth, energy per second per square meter. Luminosity pas through each sphere is the same: area of sphere: 4pi(radius)^2. The relationship between apparent brightness and luminosity depends on distance: brightness = luminosity/4pi(distance)^2, we can determine a star"s luminosity if we can measure its distance and apparent brightness, luminosity = 4pi(distance)^2(brightness) Parallax: the apparent shift in position of a nearby object against a background of more distant objects: hold your finger straight. Close your left eye close your right eye : apparent positions of nearest stars as they shift as earth orbits sun. Parallax is measured by comparing snapshots taken at different times and measuring the shift in angle to star: parallax and distance, we measure angles in arcseconds (1/3600 of a degree) P= parallax angle: d(in parsecs) = 1/p(in arcseconds, d(in light-years) = 3. 26*1/p(in arcseconds)
