Individual Exercise 1 Name: Estimating Star Temperatures Overview In this exercise, you will examine a photograph taken of the Dumbbell Nebula (M27) by Dr. Peter Powers, Department of Physics. Your interest will not, in fact, be in the Nebula, but rather the stars in the picture. The time exposure provides a representation of the surface colors of each of the stars in the field of view. If you recall from our discussion of Blackbody (Continuous) Spectra, the color of the object gives direct information about the temperature. This would be a good opportunity to review the powerpoint presentations on Continuous Spectra. You will estimate the color of 5 stars in the picture. The specific 5 stars you will analyze are identified in the Procedures (below). Open the Powerpoint Presentation “Estimating Star Temperatures.” In this presentation, you will find a photo taken by Dr. Peter Powers, Department of Physics of the Dumbbell Nebula. In this exercise, you will not focus on the Nebula, but rather the stars in the picture. If you look at the photo, you will see that the color of each star is recorded in the image, and you will also see that the image is blocked off into regions, from 1-16. In this exercise, you will estimate the temperature of 5 different stars as determined by your Researcher Number identified in your electronic gradebook site. Procedure If you look in your electronic gradebook, you will see that you have been identified with a “Researcher Number.” Your Researcher Number will be used to identify the specific 5 stars that you will evaluate. 1. From you Researcher website, click on the link to open the Powerpoint presentation with your pictures. You will get a window with a series of options. For convenience, you should save the Powerpoint file to your computer and then open it from the saved file. Saving the presentation allows the use of the viewing options listed below. Once you have the Powerpoint saved, open it from your computer and look at the information contained in the presentation. You will find some introductory material (read this material!) in the first two slides, followed by the original picture, the original picture divided into regions, and finally the picture with FIVE stars circled in RED. These circled stars are the ones you will analyze. 2. From the PHY250 website, open the link to the “Adjustable Blackbody Radiation Graph” which is under the heading “Blackbody Radiation (Continuous Spectra). You will find a slidebar which allows you to vary the location of the peak of the curve. As you move the slidebar, you will see the temperature of the object in the lower right corner of the image as well as the composite color (ie, the visual color) of an object at that temperature. 3. Record the number of the first star (probably Star #1) you are going to analyze in the table below. To get a good image of the star, you should magnify the slide. This is done using“View” in the toolbar at the top of the page. Choose “Zoom” in the window. The highest magnification of the image occurs at 400%. This setting is probably the best choice. 4. You will need to compare the color of the star with the Adjustable Blackbody Radiation Graph. You can either cycle back and forth between the two windows, or you can “half-size” each window so you can be both on the screen at the same time. This is done with the “Maximize/Restore Down” button at the very upper right corner of the window. 5. Adjust the Blackbody Radiation Graph until the composite color matches the color of the star you have chosen. Take note that the time exposure can “overwhelm” the image, so you might find a star has a color blur. Choose the color that you think best represents the star. ALSO NOTE: This is a very rough evaluation of the temperature. You do not need to try to “split hairs” about the specific temperature. 6. Record your temperature estimate, and the Stellar Classification (Spectral Type). 7. Repeat for a TOTAL of five different stars. Star Number Estimated Temperature Spectral Type Once you have completed your recordings, go to the “Working Group Exercises” link at the PHY250 website. Open the “Estimating Star Temperatures” data input form and submit your results electronically. RETAIN this sheet for future
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