AST101H1 Lecture Notes - Lecture 23: 51 Pegasi, Hot Jupiter, Doppler Spectroscopy

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

Document Summary

Objects moving toward us _ blue shift. Objects moving away from us _ red shift. It only work if that object is moving directly away or toward us. We can only measure part of the object"s speed if it is moving diagonally and we won"t be able to measure its speed if it is moving across or line of sight. Kepler"s 1st law is in fact not quite right (because planets do not orbits stars!) Both planets and stars orbit their center of mass. But most stars are much more massive than their orbiting planets. Centre of mass is close, but not at, the center of the star. Similarly, the earth orbit the earth-moon center of mass: the doppler method. The exoplanets move in large orbit, but we (cid:272)an"t see it because it"s too faint. Their parent star moves in a tiny orbit since it"s so bright, we can measure the radial velocity using the doppler effect: 1st extrasolar planet.