Spectral Classes Worksheet-1.docx

Spectral Class Worksheet These lab activities have evolved over years of use in Clemson University’s Department of Physics and Astronomy general astronomy laboratory. Contributors include Tom Collins, Mark Leising, Neil Miller, Peter Milne, Grant Williams, Donna Mullenax, Jessica Crist, Keith Davis, Amber Porter, Lea Marcotulli, and David Connick. Please direct all questions, complaints, and corrections to David Connick (dconnic@clemson.edu) who is responsible for all errors and omissions. Worksheet Name _Andrew Birchler___________ III Example Stars Table 1. Stars Spectral Class Name Temperature (K) B-V Color Index (number) Absolute Magnitude (total) Distance (ly) O Nair al Saif 31,500 -0.21 -6.50 2300 B Phact 12,700 -0.10 -2.88 261 A Fomalhaut 8,730 0.14 1.61 25.1 F Tabit 6,520 0.47 3.51 26.3 G Kraz 5,050 0.89 -0.93 146 K Wazn 4,390 1.18 0.35 87.2 M Gacrux 3,490 1.52 -2.44 88.6 1) In which properties do you see a trend as you move down the spectral class? What is the trend? B-V color index increases and Temperature decreases Table 2. Spectral Class K or G Stars Luminosity Class Name Temperature (K) Absolute Magnitude (total) Distance (ly) I Rastaban 5,190 -2.75 380 II Kraz 5,050 -0.93 146 III Vindemiatrix 4,800 -0.22 110 IV Mu Herculis 5,560 3.61 27.1 V Rigil Kentaurus 5,790 4.17 4.36

2) Which property of the star determines its Luminosity Class. How is that property changing as you move from class I to class V? Absolute magnitude determines luminosity class. Absolute magnitude increases as you move from class I to class V IV Spectral Class Spectra 3) Calculate the wavelength extremes for the visible spectrum of hydrogen (n 1 = 2): Ask your instructor for help with this calculation. Longest wavelength: ___ 6578.95 ____ Line designation (n 2 )___ 3 ____ Shortest wavelength: ___ 4166.67 ____ Line designation (n 2 )___ 6 ____ V Spectral Class Ordering 4) Using the numerical designations of the absorption spectrum plots which is the simplest plot (least dips and fluctuations)? Plot 1 has the least dips and fluctuations 5) Which absorption spectrum plot is the most complex (most dips and fluctuations)? Plot 7 is the most complex 6) In which of the absorption spectrum plots are the hydrogen lines the strongest? Plot 7 7) Which of the absorption spectrum plots is from the highest temperature source? Plot 1 8) Which of the absorption spectrum plots is from the lowest temperature source? Plot 3 9) Focus on the dips in the absorption spectrum plots due only to Hydrogen. Using the numerical designations list the spectrum from strongest (deepest) hydrogen lines to weakest (shallowest) hydrogen lines. 7, 6, 5, 4, 3, 2, 1 10) Looking at the calcium emission lines, at what wavelengths do the K and H lines appear at in Angstroms? K is at 3940 and H is at 3990 11) In which absorption spectrum plots can you see (both dips about the same size) the K and H calcium dips? Plots 2, 3, 4, and 5 all have roughly the same saze K and H calcium dips.