PROCEDURE
Step 1
(a) Go to cas.sdss.org– this is the Sloan Digital Sky Survey’s public data portal. If you wish, take a look at the “About Astronomy” and “About Skyserver” pages under the Links menu to refresh your familiarity with this powerful online scientific tool. Then click on the “Navigate” page under the Data Access menu to reach the navigation tool. Once you’re there, click on the “Objects with spectra” box under the “Drawing options” menu.
(b) In the “Parameters” menu at the upper left side, type in the RA box 179.71488 and in the Dec box –0.54345 (be sure to include the negative sign). Then click the “Search” button, and you will go to that spot in the sky. There is a star there – actually, it looks like two stars. The star slightly up and to the left has its spectrum measured; click on the graph of its spectrum in the box toward the lower right corner of the window. A large version of that spectrum should now appear in a new browser tab. Write down the u, g, r, I, and z colors of this star (look in the upper right part of the window to get them). Then sketch this spectrum as accurately as you can, being sure to label the X and Y axes with both units and numbers. Calculate the (g-r) color and write that down too. Finally, write down the stellar type and the color this star appears on your screen.
Step 2
(a) Now go to [RA = 147.21943, Dec = 23.50115] and [RA = 176.64680, Dec = 0.20929]. Write down their u, g, and r, magnitudes and (g-r) colors. These two stars have been incorrectly classified in this database as Quasi-stellar object or quasa “QSO.” What kind of stars do you think they are? Explain your answer.
(b) The following stars have been classified as follows:
RA Dec Classification RA Dec Class.
176.64680 0.20929 O4 259.34208 58.09969 B6
144.33402 23.59963 A0 138.47083 26.44388 F2
179.71488 – 0.54345 G2 175.62184 – 0.06493 K5
146.83983 23.44978 M2 138.83369 26.44241 M6
(c) The Sun has a spectral classification of G2. In a short paragraph of 30-50 words, describe how the Sun’s spectrum and colors compare with the various stars that you have classified in this laboratory exercise. There is no “right” answer to this question; write about what you have observed, with as much scientific precision as you can.