AST 2002 Lecture Notes - Lecture 16: 51 Pegasi, Orbital Period, Methods Of Detecting Exoplanets
Document Summary
A sun-like star is about a billion times brighter than the light reflected from its planets. Planets are close to their stars: planet detection. Direct: pictures or spectra of the planets themselves. Indirect: measurements of stellar properties revealing the effects of orbiting planets: gravitational tugs. The sun and jupiter orbit around their common center of mass. The sun wobbles around that center of mass with same period as jupiter. The su(cid:374)"s (cid:373)otio(cid:374) arou(cid:374)d the solar s(cid:455)ste(cid:373)"s (cid:272)e(cid:374)ter of (cid:373)ass depe(cid:374)ds o(cid:374) tugs fro(cid:373) all of the planets: this motion could determine the masses and orbits of the planets, astrometric technique. Detecting a wobble: measuring the (cid:272)ha(cid:374)ge i(cid:374) a star"s positio(cid:374) i(cid:374) the sk(cid:455, doppler technique. Measuri(cid:374)g a star"s doppler shift (cid:272)a(cid:374) tell us its (cid:373)otio(cid:374) to(cid:449)ard a(cid:374)d a(cid:449)a(cid:455) fro(cid:373) us. The orbital period of a(cid:374) u(cid:374)see(cid:374) pla(cid:374)et will be the sa(cid:373)e as period of the star"s.
