Lecture 9sun will spend like 10 billion years on the moonAST 105 1st Edition Lecture 9Outline of Last LectureI. Apparent Magnitude a. Brightness of starsII. Absolute Magnitude a. Accounts for distance as well as brightness/luminosityOutline of Current LectureI. H-R Diagramsa. Main sequence lineb. Giants and Super-giantsc. White DwarfsII. Spectroscopic ParallaxIII. Mass-Luminosity Relation Current LectureH-R Diagram - About 100 years ago, Hertzspring and Russell noticed a relation between the stars surface temp. and luminosity in their namesake diagrams Relation between surface temperature and luminosity - Stars with high surface temps generally have large luminosities- 91% of stars are on the main sequence line- Giants and super Giants – relatively cool surface temps but high luminosities Cool stars with large luminosities- About 1% of all stars are giants or super giants- About 8% of all visible stars are white dwarfs- White dwarfs have high surface temperature and low luminosity - Giants typically have a radius that is 10 to 100x larger than the radius of our sun - Super Giants 1000x larger than the radius of our sun Spectroscopic Parallax- A way to determine the distance to far away starsThese 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.- First measure the amount of light we get here on earth (apparent magnitude)- Then find surface temp and type- Pin down location on the H-R diagram - M = m – 5Log10(d/10) D=10(m+5-M)/5- d= distance to the star in parsecs Mass-Luminosity- main sequence stars, the more luminous the star, the more massive the star sun will spend like 10 billion years on the
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