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Name:Page 1Date:Lab 10. Stellar Spectroscopy & The H-R DiagramIntroductionIn this lab, we will first watch a movie segment on stellar spectroscopy.Then we will construct and use an H-R diagram to compare the properties of two groupsof stars: the closest stars and the brightest stars.On an H-R diagram stars are plottedvertically according toLuminosityand horizontally according toSpectral ClassorSurface Temperature.Part A. Questions about the movieWatch the video segmentaon stellar spectra and the pioneering work of Annie Jump Cannonand Cecelia Payne. Then, together with your classmates, answer the questions below.aWatch from the beginning up to the 25:38 mark.1. What is the purpose of the wedge of glass Rick Hill mounted on the front of his telescope?2. What was the purpose of the segment of the film photographed in black and white?3. What method did Annie Jump Cannon use to rearrange the spectral classes into the currentsequence 00, 01, ... B ... A ... F ... M8, M9? HINT: Think about morphing.4. Some stars show strong calcium lines in their spectrum; in others these lines are weak.a. Before Payne, what did most astronomers think was the reason for this difference?b. What did Payne’s work show is really the reason?
LAB 10.STELLAR SPECTROSCOPY & THE H-R DIAGRAMAstronomy 105. What did Payne’s work demonstrate abouta. the significance of the sequence O0, O1, ..., B, ..., A, ..., F, ..., M8, M9? What does itreally measure?b. the basic “recipe” (chemical composition) of the stars?6. According to the narrator, what is the significance of the fact that stars are mostly made ofH and He?Part B. The H-R DiagramStudyTable 10.1below. It gives the colors and surface temperatures of typical stars of eachof the seven spectral classes. You will need to use this table many times during this lab toanswer various of the questions, so don’t forget it!Table 10.1: Colors and Surface Temperatures of the Spectral ClassesSpectral ClassOBAFGKMColorblue-violetbluewhiteyellow-whiteyelloworangeredTemperature30,000 K20,000 K10,000 K7000 K6000 K4500 K3000 KStudy the typical H-R diagram below inFigure 10.1. Make sure you understand what is plottedvertically and what is plotted horizontally. Identify and study the four groups of stars on thediagram. Note that the Sun is right in the middle of the main sequence, has a luminosity of 1and a spectral type G2.Main Sequence:Most stars lie on this diagonal band. There are many more cool faint starsthan hot bright stars.White Dwarfs:These stars are extremely hot and yet very faint. Therefore, they must bevery tiny.Giants:These stars are relatively cool and yet very bright. Therefore, they must be enormousin diameter.Super Giants:These stars are huge, hot, and extremely bright.2

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Term
Fall
Professor
Homer
Tags
Sirius, Stellar classification, Alpha Centauri

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