AST101H1 Lecture Notes - Lecture 22: Doppler Spectroscopy, Exoplanet, Orbital Period

• School: UTSG
• Department: Astronomy and Astrophysics
• Course: AST101H1
• Professor: Bryan Gaensler

Document Summary

Sources moving towards you shift to a higher frequency (shorter wavelengths) (blue) Sources moving away from you shift to a lower frequency (longer wavelengths) (red) Doppler only measures line of sight: an object moving directly away: we measure all of its speed. Moving across our line of sight: we measure none of its. Moving diagonally: we measure only part of its speed. In all cases, only the part of the motion we can measure is speed the radial velocity. Keplers 1st law: planets orbit the sun in an elliptical pattern, with the sun at one focus. A little bit wrong: planets do not orbit stars. Planets and stars orbit their common centre of mass. Most stars are much more massive than their planets: Therefore, centre of mass is close to but not at the center of the star. From our perspective, the star wobbles toward us & away from us.