ASTR 2010 Lecture Notes - Lecture 7: Apparent Magnitude, Jigsaw Puzzle, Electromagnetic Spectrum
Document Summary
The hot, low pressure gas is not capable of emitting all of the colors of visible electromagnetic spectrum, and therefore it produces a bright-line or emission spectrum. Since each atomic level has a certain energy requirement, only certain amounts of energy can be absorbed by the electrons. By examining the complicated absorption spectrum that results, astronomers are able to deduce which elements are in the star"s atmosphere. Such stars may be distinguished as binaries if their orbits are sufficiently inclined to the sky (seen more or less edge-on). The stars alternately approach and recede from the earth as they revolve about their common center of mass. The motion produces a doppler effect, which is detected as a back-and- forth shift of the stellar spectral lines -- the dark absorption lines in stellar spectra. In some cases, two sets of spectral features are seen (one for each star) oscillating in opposite directions.
