Spectral Classes Worksheet-1

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 III Example Stars Table 1. Stars Spectral Class Name Temperature (K) B-V Color Index (number) Absolute Magnitude (total) Distance (ly) O Zeta Ophiuch 32000 .02 -5.93 460 B Spica 26200 -.13 -5.95 250 A Sirius A 9400 .02 1.21 8.7 F Muceti 7300 .32 2.11 84.1 G Alpha Centauri A 5790 .69 4.17 4.36 K Gienah 4660 1.03 .25 72 M Menkar 3620 1.63 -3.31 220 1) In which properties do you see a trend as you move down the spectral class? What is the trend? a) As the spectral classes move from left to right, the temperature decreases with each class. In the opposite direction, from right to left, the color index increases with each class. In absolute magnitude, from left to right, the numbers begin small, increase to positive values, then decrease back to negative. In distance, from left to right, the numbers start large, then decrease, then increase again. Table 2. Spectral Class K or G Stars Luminosity Class Name Temperature (K) Absolute Magnitude (total) Distance (ly) I Beta Camel- opardalis 5280 -3.29 1000 II Rastaban 5190 -2.75 362

III HR1129 5850 -2.81 450 IV 12 Comae Berenices 5850 -.18 295 V Achird 5940 4.40 19.4 2) Which property of the star determines its Luminosity Class. How is that property changing as you move from class I to class V? a) The absolute magnitude of the star determines the luminosity of the star. The property changes through the classes because it ranges through negative and positive values. 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 A Line designation (n 2 ) = 3 Shortest wavelength: 4166.67 A 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)? a) Graph 1 is the simplest plot. 5) Which absorption spectrum plot is the most complex (most dips and fluctuations)? a) Graph 7 is the most complex plot. 6) In which of the absorption spectrum plots are the hydrogen lines the strongest? a) Graph 7 has the strongest Hydrogen lines. 7) Which of the absorption spectrum plots is from the highest temperature source? a) Graph 1 has the highest temperature source. 8) Which of the absorption spectrum plots is from the lowest temperature source? a) Graph 3 has the lowest temperature source. 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. a) 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? a) K is located at 3940 angstroms and H is located at 3990 angstroms.