ASTR 103 Lecture Notes - Lecture 13: Semi-Major And Semi-Minor Axes, Subgiant, Spectroscopy
Document Summary
Angle) ( d istance=1/ parallax against the background stars observed as the earth moves along its orbit are much more accurate than those made with earth-based telescopes. Parallax: a change in relative position noted due to a change in location of observer. Careful measurements of the parallaxes of stars reveal their distances. Distances to the nearer stars can be determined by parallax, the apparent shift of a star. Stellar parallaxes can only be measured for stars within a few hundred parsecs. If a star"s distance is known, its luminosity can be determined from its brightness b = l/4 d^2. ~ b: apparent brightness of a star"s light, in w/m^2. ~ d: distance to star, in meters are related by the inverse-square law. If any two of these quantities are known, the third can be calculated. A star"s luminosity (total light output), apparent brightness and distance from the earth. Stars of relatively low luminosity are more common than more luminous stars.
