i. O B A F G K M L Te. Brown dwarfs are too small to sustain thermonuclear reactions in the corea. L = 4*pi*R^2*sigmaT^4 (L is luminosity and you can find luminosity from distance and you can find T from Wien’s law)b. A cool star can be bright if it has a very large radiusa. More massive star is closer to the center of mass than the last massive star the orbit of the more massive star is going to be smaller and the two stars of different masses will always be on opposite sides of the center of mass, the stars will never collide.b. The concept of Center of MassASTRON 89 1st Edition Lecture 17Outline of Last Lecture I. Properties of Stars: Distance II. Properties of Stars: Luminosity and Apparent Brightness III. Classifying Stars: Spectral ClassesOutline of Current Lecture I. Properties of Stars: The spectral sequence of TemperatureII. Properties of Stars: Stellar Sizes III. Binary Stars Current LectureI. Properties of Stars: The spectral sequence of Temperaturea. The spectral sequence of Temperature!b. OBAFGKM i. The hottest stars are “O” stars (“M” stars are coolest)ii. Sub classes: B0 – B9 is hotter to cooler 1. Absorption lines can occur only if these stars have surface temperatures above 25000iii. Surface temperature can be known based on the strengths of the lines in the absorption spectrac. Surface Temperature affects stellar spectra i. Line strength vs. temperature of the star ii. The curve that you see tells you how much Hydrogen you actually see1. For H lines to be prominent in a star’s spectrum, the star must be HOT ENOUGH so that the electrons are out of their ground states, but also NOT so hot that they become ionizeda. The “sweet” spot where most of this absorption occurs is based upon these factorsb. The elements and their individual energy levels and the temperature of the star itselfd. The classes extend a couple of letters i. O B A F G K M L T e. Brown dwarfs are too small to sustain thermonuclear reactions in the core i. They are not stars (star Is defined as a hot object able to fuse helium in the coreThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.II. Properties of Stars: Stellar Sizes a. L = 4*pi*R^2*sigmaT^4 (L is luminosity and you can find luminosity from distanceand you can find T from Wien’s law) b. A cool star can be bright if it has a very large radiusc. A very hot star can be dim if it has a very small radiusIII. Binary Stars a. More massive star is closer to the center of mass than the last massive star the orbit of the more massive star is going to be smaller and the two stars of different masses will always be on opposite sides of the center of mass, the stars will never collide. b. The concept of Center of Mass c. These stars are balanced because they’re sitting on either side of the center of mass, and that distance depends on their