AST-1002 Lecture 9: Stars
Document Summary
The apparent brightness of a star is determined by distance and intrinsic brightness (luminosity or l) Parallax: the apparent angular shift with respect to background objects; the change in position caused by a change in position of the observer. The greater the parallax, the smaller the distance. The parallaxes of real stars are tiny and typically measured in small fractions of a degree known as arcseconds. Equation between parallax and distance: p (arcsec)= 1/d (arcsec) Hotter = peak of wavelength in planck spectrum is more towards the blue. Use energy level diagrams to represent the allowed energy states of an atom. Atoms exist in one allowed energy state at a time. Spectra of stars were first classified in the late 1800s. Today we order stars based on temperature. Hottest stars: o type in general blue with weak hydrogen and helium absorption. Hotter stars emit more light per square patch. Use luminosity and temp to calculate radius.
