AST 115 1st Edition Lecture 24 Outline of Last Lecture I. Spectral Classificationa. OBAFGKMII. Types of Starsa. H – R DiagramIII. Binary Starsa. William Herschelb. “Optical Double”c. Categories of Binariesi. Visualii. Astrometriciii. Spectroscopiciv. EclipsingOutline of Current Lecture I. Measuring Masses with Visual Binariesa. Newton’s Revision of Kepler’s 3rd Law and ExampleII. Measuring Diameters with Eclipsing BinariesIII. Normal Ranges in Stellar Parallaxa. Diameterb. Massc. Luminosityd. Surface TemperatureIV. Intro to Stellar Evolutiona. “Golden Rule”b. Stages of Stellar EvolutionIntro to Chapter 11: The Lives of StarsI. The Interstellar Mediuma. Gasb. DustII. Intro to Types of Nebulasa. BrightCurrent Lecture Measuring Masses With Visual BinariesThese 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.o You cannot measure mass of an isolated star. You must used Newton’s Revision ofKepler’s 3rd Law:(M1+ M2) P2= a3 - Example: If P = 8 years and separation (a) = 4 A.U., then (M1+ M2¿=a3/ P2 =43/ 82 = 64/64 = 1 M⊙ Measuring Diameters with Eclipsing Binarieso Light curve of an eclipsing binary gives the relative diameters of the two stars. Normal Ranges in Stellar Parallaxo Diameter 1/100 to 700 D⊙ (of the Sun)o Mass 1/10 to 100 M⊙ o Luminosity 1/10,000 to 1,000,000 L⊙ o Surface Temperature 2,500 to 50,000 ˚K Introduction to Stellar Evolutiono Although stars appear to be unchanging, their properties do slowly change. Stars develop or evolve with time.- Example: If you’re in a forest, you wouldn’t star at one tree for years on end to watch it change. You would study all of the specimens in the forest and deduce the changes.o “Golden Rule” of Stellar Evolution:- The more massive a star, the faster it evolves.o The use of the H – R Diagram is important to study stellar evolution.o There are different stages of stellar evolution:- Pre-Main Sequence Stage- Main Sequence Stage- Post-Main Sequence Stage- EndpointsIntroduction to Chapter 11: The Lives of Stars The Interstellar Medium (ISM)o Interstellar space is not completely empty. The presence of gas and dust is indicated by its effects on star light.o Nebula = “cloud” in Latin. (Plural: Nebulae; or Nebulas)o Gas → individual atoms of any type or molecules of any type.- Typical density = 1 atom/cm3, or 1,000 molecules/cm3o Dust → collections of thousands or millions of atoms stuck together.- Typical density = 1 particle per cubic kilometer Types of Nebulaso Bright (or emission) = Red light from hot (10,000 ˚K) hydrogen gas. Due to hot stars in the gas. (Also called H II
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