ASTR 1102 : Exam 2 Notes
Document Summary
A star is bright because it is luminous, hot, big and/or close. Sun: every star has a parallax less than 1 arcsec, from earth, we can"t measure farther than 100 pc, from space we can see several hundred pc. Brightness the apparent intensity of a star"s light. (w/m^2: how much brightness we see/reaches us. H-r diagram: lets us understand relationships between stars and lets us understand how stars age. Stefan-boltzmann equation relates the energy flux from the surface of the object to the temperature: radius of the sun = 1. Spectra and temperature: all stars have a similar composition, 75% he, 25% he, <1% metals, the hotter the star, the less apparent the absorption lines, kirchoff"s 3rd law, at different temperatures, different elements/compounds are found in absorption lines. Spectral classes: oh be a fine girl/guy, kiss me, o = hottest, m coolest. Luminosity classes: the higher the roman numeral, the lower the luminosity.
