07Lab_The-Milky-Way

M ONTGOMERY C OLLEGE – R OCKVILLE A STRONOMY 101 ASTR101 Laboratory 7 - The Milky Way 1 Name: For thousands of years people assumed that the stars they saw at night were the entire universe. Even after telescopes had been invented, the concept of a “galaxy” was a difficult one for people to grasp. The idea that we live in one of billions of “island universes” was so mind-blowing that it took many decades to be accepted. Understanding first that we live in something called the Milky Way Galaxy, and then that there billions of other galaxies like ours in the universe was a huge task! PART A The first step to understanding our universe is noticing that the stars are not uniformly distributed across the sky. There are certain areas of the sky that have more stars than others. Let's see if we can see where that part of the sky is located.  Start Stellarium . Turn off the Atmosphere and Fog. (The sky should be dark.) Zoom out and move the ground around until you can see the whole sky. We want to display only the stars- no star names, no planets, no constellations or constellation names, and no nebulae.  Open the Sky and viewing options menu. In the Sky submenu, under the Stars section on the right, uncheck the Labels and Markers box.  In the Sky submenu, under the Stars section on the right, change the Absolute scale to 1.5 and the Relative scale to 0.35 . This makes all the stars appear to be the roughly the same size, as they really do in the sky.  In the SSO submenu, uncheck the Solar System objects box.  In the Starlore submenu, uncheck all boxes under Options .  Close the menu and change the Date & Time to July 6, 2021 , at Midnight . You are looking at the sky as it would appear in a VERY dark location in the middle of summer at Midnight. Do the stars look like they are evenly distributed throughout the sky, or do they look like there are more stars in one part of the sky than another? It looks like the sky has more starts in one part of the sky specifically around the south 1 Last edit Spring 2022. 1

ASTR101 L ABORATORY 7 Since the beginning of time, people have noticed that there is a faint, milky-white band of light that spreads across the sky. Do you see the Milky Way in the sky? It's difficult to see, both in real life, and in Stellarium , unless you are looking in very dark conditions. Try turning off the lights in the room where you're doing this assignment, if possible. Does the Milky Way correspond to the part of the sky where you saw more stars? Yes, it does The band across the sky where you see many more stars corresponds to the Milky Way. You can see this band in the sky on a dark night away from city lights. Display the constellations (and their labels ) and list below at least 8 of the constellations that the Milky Way passes through. You may want to let time pass so that you catch all the constellations through which the Milky Way passes: - Cygnus - Sagittarius - Scutum - Cassiopeia - Sagitta - Aquilla - Scorpius Now let's compare the number of stars along the Milky Way with the number far away from it, to see if the stars are evenly distributed throughout the sky.  Use the View menu and the Markings submenu to enable the Galactic Grid and Galactic Equator .  Now click anywhere along the disk of the Milky Way, and center on that spot by pressing the Space bar. Zoom in until the Field of View is 1° . Remember, the Field of View (FOV) is listed in the Information Bar at the bottom of the screen.  Count the number of stars on the screen. Enter the value in the Table 1 below next to “Milky Way 1.”  Now zoom back out and click on a different random spot along the Milky Way and do the same thing. Enter this star count as “Milky Way 2.” Do the same for a total of five random Milky Way star counts.  Now click near North Galactic Pole (NGP). The NGP is toward the constellation Coma Berenice s. Again, zoom in to a 1° field of view and count the stars at the North Galactic Pole. Enter this Star Count in the table. Do the same for the South Galactic Pole (SGP). The SGP is toward the constellation Sculptor . 2