ASTR 152 Lecture Notes - Lecture 6: Parsec, Sun-1, Foula
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Stars: their observed physical properties: from direct observation, using mainly optical telescopes equipped with various detectors, we want to find: Temperature (in kelvin), total energy output (luminosity), size (radius), mass, distance, composition, and motion (how fast and in which direction). If em radiation is dispersed into various wavelengths, by a spectrograph, there may be three different types of radiation or spectrum: continuum spectrum continuous radiation. Produced by anything that has a temperature above 0 k. K(cid:374)o(cid:449)(cid:374) as (cid:862)the(cid:396)(cid:373)al (cid:396)adiatio(cid:374)(cid:863) o(cid:396) (cid:862)(cid:271)la(cid:272)k (cid:271)od(cid:455) (cid:396)adiatio(cid:374)(cid:863) The higher temperature an object has, the more radiation it gives off. Hot objects emit more intensely at short wavelengths, while cold objects emit more intensely at long wavelengths. Spectral lines are used to find out many things about objects from which the come. The sun and other stars give off radiation with dark lines (absorption) Nebulae give off radiation with bright lines (emission) The(cid:374), from trig. , a simple formula is used:
