ASTRONOMY 105 Observational Astronomy Lab H Data Sheet Name Lab H: Size and Shape of the Galaxy Procedure 1 Questions: 1. Look at the R.A. and Dec plot of the clusters in Figure 4. Is there a pattern or grouping in one area, or are the clusters distributed randomly around the sky? 2. Now look at your plot and estimate the center of the distribution of the globular clusters (and the center of the galaxy). Mark a large X where you think it is. Write down the RA and Dec of this center. RA = Dec = 3. From Figure 4, is your estimate of the position of the galactic center to the North or South of the Celestial Equator? a. North b.South c. On the Celestial Equator (Circle a, b, or c) 4. How many degrees North or South is the galactic center? Procedure 2 Questions: First, we must find the luminosity of the Cepheid variable from the period-luminosity chart in Figure 2, in the Instructions: For the Cepheid in M56, its period is 2.05 days. To do this, look at Figure 2. Find 2.05 days along the bottom of the chart, then go up to the red line. Move horizontally to the left to find Luminosity of this star. (Hint: Use 103 to make things easier) 1) What is the corresponding luminosity of this Cepheid? Second, we must convert this luminosity to an Absolute Magnitude (M). The absolute maghnitude is how bright the star would be if it was only 10 parsecs away. This formula is M=4.83-25log(L) (Note:the Log (10%) =3) 1