ASTR 114 Lecture Notes - Lecture 27: Giant Star, Binary Star, Main Sequence
10 Jan 2020
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Lecture 15: sb, sm, sm, sr part ii. Orbit of binary star system depends on strength of gravity. More unequal masses, the more center of mass shifts to more massive star. Visual binary star system: both stars seen directly, separation and relative motion can be followed directly. Spectroscopy binary star system: determine orbit using doppler shift. Eclipsing binary star system: sometimes you can see light from both stars, other times brightness of 1 of the stars is lowered/eclipsed) Newton"s version of kepler"s third law for binary systems: m + m = a^3/p^2. Cannot determine each mass though; need to substitute with law of torque (m1r1=m2r2 or m1v1=m2v2); solve for one of masses, plug into third law, then use algebra. Color of a star is indicative of its temperature: red stars = cool, blue = hot. Obafgkm, subclasses (0-10, ex: sun is g2) is harvard (henry draper) classification. O = hottest stars, m = coolest stars.
