ASTR 3 Lecture 3: Astronomy 3 Lecture 3 Notes
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Thermal radiation: nearly all large/dense objects emit radiation. Thermal radiation coming from sun and virtually all objects follow a curve similar to the blackbody curve when plotted with frequency. Radiation from sun peaks at around visible light wavelength. With much hotter stars, the radiation peak shifts to the right of frequency. Hotter objects emit more light at all frequencies per unit area. Hotter objects emit photons with higher average energy. Therefore, a cooler star can emit more tatal energy if the cooler star is much larger in size. Luminosity, the total energy radiated every second = (sigma) t 4 x 4. Use stefan"s law to determine how much power a star emits per (pi) r 2 . 4 (pi) r 2 is the surface area of the star. square meter given temperature. Then, use wien"s law to determine its wavelength of peak intensity.
