Lab 1 Locating Objects in the Night Sky Celestial Coordinates - DOC - DOC

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Lab 1 Locating Objects in the Night Sky Celestial Coordinates - DOC - DOC Powered By Docstoc
					Geol 4110: Advanced Earth Science for Teachers Spring 2009

Name_______________________________________

Locating Objects in the Night Sky: Celestial Coordinates, Time, Angles In this lab exercise we will explore methods of finding objects in the night sky, telling time in a couple of different ways, and measuring angles. You will also get and introduction to the Messier objects, the deep-sky objects cataloged by Charles Messier between 1753 and his death in 1817. For this exercise you need Stellarium software. Stellarium – is a free download www.stellarium.org Objectives: These exercises are designed to provide hands-on learning experiences in observational astronomy. The session will give you the opportunity to work on the material with help from the instructor. This is a homework assignment. I. Measuring Distances and the Horizon Grid 1. Launch Stellarium. Position your mouse in the lower left corner of the screen to bring up the pop-up menus. Find the “Location” option and set to Duluth, Minnesota. Record the latitude __________ and Longitude __________ of Duluth as tabulated in Stellarium. 2. Position your mouse in the lower left corner of the screen to bring up the pop-up menus. Find the “Date/Time window” and set the time to 9:00 pm tonight. 3. Use the Search Window and find the North Star (Polaris). Position your mouse in the lower left corner of the screen to bring up the pop-up menus. Turn on the “Azimuthal” or “Horizon Grid” and determine how far above the northern horizon the north star is in degrees (˚) (and minutes („) is you can) of arc? __________. How does this compare to the latitude of Duluth? __________ 4. You should see the asterism the “big dipper” in the northeastern sky. Click each of the stars in the big dipper and record their names. __________, __________, __________, __________, __________, __________, __________. Merak and Dubhe are known as the pointer stars because they point to the North Star in one direction and to the star Regulus in the constellation Leo in the opposite direction. 5. Using the horizon grid, determine the angular separation of Alkaid and Dubhe in ˚: and mm. __________. II. Coordinates: The Horizon Grid 1. Using the horizon grid, estimate the altitude and azimuth of Merak. Alt ________; Azimuth ________. a. Now you can check your estimate. Click on Merak so that it is highlighted. Look at the “Info” pane on the upper left side of the screen. Record the actual positions. Alt ________; Azimuth _________. b. Why are the values constantly changing? 2. While looking north, adjust the screen so you can see the North Star and the northern horizon. Set the time flow to run forward so the stars are rotating rapidly. Notice that the big dipper reaches its lowest point in the sky but is still above the horizon. This means that the big dipper is always visible from our

Geol 4110: Advanced Earth Science for Teachers Spring 2009

Name_______________________________________

location, and as you can see, circles the pole star, Polaris. Objects that are always visible from a location are referred to as “circumpolar.” c. If you are located at approximately 46˚ N as we are here in Duluth, objects out to what radial distance from Polaris will be circumpolar? __________ d. If you were located in Florida at 36˚ North latitude, objects out to what radial distance from Polaris will be circumpolar? __________ 3. Reset the time to 9:00 pm today. Click on the “Find” pane on the left side of the screen. Type in the star name “Arcturus” and press enter. What constellation is Arcturus in? _________. What kind of object is Arcturus? __________. Determine its Altitude above the horizon. Alt __________. 4. From the Viewing options menu select Markings and turn on the local meridian. The night sky is generally divided into eastern and western hemispheres by the local meridian. III. Coordinates: The Equatorial Grid (Right Ascension and Declination). 1. Turn off the horizon grid and turn on the equatorial grid. The equatorial grid is divided into 360˚ in both right ascension (RA) and declination (Dec). Declination is measured in degrees north or south of the celestial equator. Right ascension, however, is divided into 24 hours. a. One (1) hour of right ascension is equal to how many degrees of arc? __________ b. One (1) minute of right ascension is equal to how many minutes of arc? __________ c. One (1) second of right ascension is equal to how many seconds of arc? __________ 2. Using the celestial grid: (Hint: you will need to change the time of the day a. Estimate the RA and Dec of Altair from the celestial grid. RA __________; Dec __________ (TIP: if you zoom in using the mouse scroll wheel or the + and – keys the celestial grid will increase in resolution. b. Click on Altair to bring up the information and record the exact RA ________; and Dec __________. c. Why is the RA and Dec of the object NOT changing? 3. From the Viewing options menu select Markings and turn on the ecliptic. Look to the SE sky and find the location where the ecliptic crosses the celestial equator (you may need to zoom in slightly to see the celestial equator). What are the RA and Dec of the point where the two reference lines cross? RA__________; Dec__________ a. This point is one the “cardinal points” in Earth‟s orbit. What is the significance of this point? 4. Increase the time flow and move forward until the Sun is well up into the sky. Notice the Sun is on the ecliptic. a. Stop the time flow by clicking the stop button. b. Click on the Sun and bring it to the center of the screen. c. Turn on the local meridian. d. Set the time to 13:10 hours. e. Move forward 1 day at a time by pressing the = sign. Simply observe the Sun as it changes position relative to the ecliptic and the meridian throughout the year. The Sun is always on the ecliptic because it is the Sun that defines the ecliptic.

Geol 4110: Advanced Earth Science for Teachers Spring 2009

Name_______________________________________

f. Cycle through a year by pressing and holding down the = sign key. Notice how the sun forms a figure-eight about the meridian. This figure 8 is the “analemma.” Do a little research and describe why we see this form when advancing one average solar day at a time. Why the Analemma:

IV. Where is the Sun? 1. What is the best time to view the constellation Orion? Well, that would be when Orion in high in the nighttime sky. So when is that? a. Find the R.A. of any star in the constellation Orion. _________ b. What should the R.A. of the Sun be to give you the best view of Orion? ________ c. Now determine what month that will be. i. What is the R.A. of the Sun on the vernal equinox? ________ To determine this consider that there are 24 hours of R.A. in the celestial grid. The Sun makes one trip around the celestial grid in a year. The 0h 00m 00s R.A. point on the celestial grid is defined by the position of the Sun on the vernal equinox. Therefore since there are 24 hours of motion in 12 months, then the R.A. of the Sun changes by 2 hours R.A. each month. Approximate date Sun Position (R.A.) March 21 0h 00m June 21 6h 00m Sept 21 12h 00m Dec 21 18h 00m V. Latitude change 2. Change your location to somewhere on the Equator. a. Look to the north. Where is Polaris (north star)? b. Look to the East. Run the time forward at increased speed. Observe the stars rising in the east and determine the angle the rising stars make with the horizon. Angle = __________. 3. Change your location to St. Louis, Missouri. a. Look to the north. Find Polaris (north star) and determine its elevation above the horizon using the arc measuring tool. This will also be the latitude of St. Louis. Elevation/Lat __________ b. Look to the East. Run the time forward at increased speed. Observe the stars rising in the east and determine the angle the rising stars make with the horizon. Angle = __________. 4. Change your location to the North Pole. a. Where is Polaris (north star)? _________________

Geol 4110: Advanced Earth Science for Teachers Spring 2009

Name_______________________________________

b. Look at any horizon. Run the time forward at increased. What is the rising angle of stars if you are located at the North Pole. Angle = __________. 5. Devise a simple equation of the following form that describes your latitude as a function of the rising angle of stars. Use the form c – rising angle = latitude, where c is a constant. (i.e. figure out the value of c) a. Write equation here _______________________________________ VI. Messier objects Charles Messier charted 103 deep-sky objects during his observing career. Deep sky objects are non-stellar objects such as galaxies, nebula, open star clusters, globular star clusters, and other objects that are beyond the solar system. 1. Using the “Find” option, type M1 and press enter. You may need to turn off the atmosphere effect to darken the sky. a. Zoom in on the object using the scroll-wheel on the mouse until the image of the object appears. i. What is the common name of M1? __________ (Hint: Use the info pane or go to www.wikipedia.com) ii. What kind of object is M1? _____________________ 2. Using the “Find” option, type M13 and press enter. You may need to turn off the ground effect to see the object. a. Zoom in on the object using the scroll-wheel on the mouse until the image of the object appears. i. What is the common name of M13? __________ (Hint: Use the info pane or go to www.wikipedia.com) ii. What kind of object is M13? _____________________ 3. Using the “Find” option, type NGC1432 (M45) and press enter. a. Zoom in on the object using the scroll-wheel on the mouse or the +/- keys until the image of the object appears. i. What is the common name of M45? __________ (Hint: Use the info pane or go to www.wikipedia.com) ii. What kind of object is M45? _____________________ 4. Using the “Find” option, type M31 and press enter. a. Zoom in on the object using the scroll-wheel on the mouse or the +/- keys until the image of the object appears. i. What is the common name of M31? __________ (Hint: Use the info pane or go to www.wikipedia.com) ii. What kind of object is M31? _____________________ 5. Using the “Find” option, type M57 and press enter. a. Zoom in on the object using the scroll-wheel on the mouse or the +/- keys until the image of the object appears. i. What is the common name of M57? __________ (Hint: Use the info pane or go to www.wikipedia.com) ii. What kind of object is M57? _____________________


				
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