ASTR 3 Lecture Notes - Lecture 11: Orbital Period, Subgiant, Bright Giant
Document Summary
Depends on luminosity and distance apparent brightness = flux = Parallax (cid:3013)(cid:2872)^(cid:2870) (units = watts/m2) d = 1/p (units: d parsecs, p arcsecs) * 1 parsec is the distance that gives a parallax angle of 1 second of arc = Laws of thermal radiation every object emits thermal radiation w/ a spectrum that depends on its temperature: hotter objects emit more light at all wavelengths. Stefan-boltzmann law: luminosity/sq meter = constant * t4: hotter objects emit light at shorter wavelengths (higher frequencies) Wien"s law: t = (cid:2870),9(cid:2868)(cid:2868),(cid:2868)(cid:2868)(cid:2868) (cid:2933)a(cid:2932)elen(cid:2917)t(cid:2918) (units: t k, wavelength nm) (hottest) Lines in a star"s spectrum correspond to a spectral type that reveals its temp. About half of all stars are in binary systems. When one star passes in front of the other there is a change in brightness. Periodic eclipses implies orbital period; duration gives radius. Orbital motion causes a doppler effect in the spectrum.
