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Observing the Sky Introductory Astronomy lab starter with Stellarium

Astronomy begins with looking at the sky. For thousands of years human beings have watched the sky at night, carefully noting the positions of the stars and planets, and how they change as the hours, days and months go by. Until modern times, knowing the sky was a matter of life and death for many – such as for farmers and planting, or for nomads and migration. To make observations of the night sky easier over the millennia, people developed various names for both stars and groups of stars, which are called constellations. Objective: In this exercise we will become familiar with the application Stellarium to simulate observation of the night sky. We will see what stars and constellations, and other sky objects, are visible, and try to understand sky motion. (To install Stellarium on your PC, Mac or Linux, go to www.stellarium.org. Check your school laboratory computer as well. Stellarium is also available as an app for smart devices running iOS or Android but is not appropriate for this course) Current Location: Germantown, Maryland (or Washington DC) Current Time: 9:00 pm, Today – Pay attention to 24-hour setting in Stellarium Highly Recommended: 1) Use a mouse, 2) Use partial screen view (see below). PART A: Your Local Night View

Start Stellarium. Use “Current Location” listed above by going to the Icon Bar at the left-hand side of the screen and find the Location window icon (shortcut key= “F6”, in some linux it is fn-f6) and click on it. Scroll through the list of locations in the window until you find the current location and click on it. If you cannot find your city then use either a nearby big city or input the exact the latitude and longitude (you can do an online search). Check that the chubby red arrow showing up in the mini atlas points to the right place – you could actually be setting in a different place like Paris without knowing. Close the Location window. You should see something similar to Figure 1 - the local horizon view. The default Stellarium setting uses current date and time showing time elapse (progressing in time). The 3 basic manual operations for screen view are: 1) dragging the screen left or right to adjust directional view 2) scrolling to zoom in or out of the view 3) dragging the screen up or down for a sky-centered or a ground-centered view The bottom icon bar will pop upward when you move the cursor near the bottom. It controls various viewing conditions and so let’s set some of them.

- Turn on “Constellation lines”, “Constellation labels”, “Ground” and “Planet labels” - Turn off “Atmosphere” (shortcut=”a”) and “Constellation arts” - Turn on “Cardinal points” which shows the four direction marks (N, S, E and W) - The “Full screen mode (F11)” is recommended to be off so that Stellarium occupies only

partial computer screen to leave room for other application display

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Drag the view left or right, but keeping the horizon view as shown in Figure 1, until your are viewing the Northern Horizon, marked by the red letter “N” on the screen. Scroll to zoom out to about 50° FOV (Field of View) - you can find FOV value at Status Bar at the bottom of the screen. Q. Name a few sky objects in your northern horizon view that you can recognize or heard of. Click on the “fast forward” button (double arrow button - “Increase time speed (L)”) just a few times until the sky rotates fast enough to clearly see star motions, but not too fast. Remember you should be in a horizon view similar to Figure 1, looking directly at “N” at the center. If not, use the 3 basic screen operations listed above to adjust. Q. Follow some stars or sky object that are moving very near the northern horizon “N” point. In what direction or in what matter are they moving? Are they moving east-west, in the northern direction, diagonally across the sky, or what?

Figure1:Standardhorizonview

Figure2:Sky-centeredview

Scroll to zoom out to 90° FOV, and drag the Northern Horizon “N” to the bottom of your screen. This way you are creating a “Sky-centered view” similar to Figure 2 but not quite full view. This is to make some quick observations and we will do more sky-centered views just a little later on. Q. Does the sky rotate clock-wise (cw) or counter-clock-wise (ccw)?

Q. Are stars in the sky rotating at the same or at different rates? Do they go around a circle at the same rate, meaning they will complete one rotation at the same amount of time, or not?

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Q. Observe carefully the sky and star movements. There is one special star right above northern horizon that does not appear to move even as all other rotates. Click on that star and see the info display shows up on the upper left-hand side. What is that star? Q. Some Ancient minds thought the sky revolves around Earth. Do sky motions (simulated by Stellarium) appear to be consistent with and support this idea? Zoom back in to 50° FOV, drag the screen back to a local horizon view, but now drag the Eastern Horizon “E” to the middle your screen. Q. For stars very near the Eastern Horizon, what direction are they moving relative to the horizon? Drag the Western Horizon “W” to the center of your screen in the local horizon view. Q. For stars very near the Western Horizon, what direction are they moving relative to the horizon? Now let’s go to a full sky-centered view as in Figure 2. Zoom out by scrolling until FOV is about 180°. Then drag the horizon around until the sky is centered on the screen and North is at the top. You should see the sky as a central circular region (see Figure 2), centered on your screen, with the horizon (North, West South, East in clock-wise order) forming the edge of the circle, and the ground as the surrounding exterior. The zenith, the direction directly overhead, will be the center of the sky region. Move your mouse over the status bar at the bottom and to see the bottom icon bar. Turn off atmosphere off. Now you should see a sky full of stars, and perhaps some planets and asteroids. You have been forewarned that Stellarium exhibits the sky motion elapsing in time, and so if the clock is not paused you may find yourself getting strange answers later on as you work through this lab. So pause the time by clicking on the play/pause button on the bottom icon bar - a “right-pointing triangle” means time is elapsing, and a “double-bar” means that the time is paused. Set for “Current Time” by clicking on the Date/Time icon on the left-hand side of the screen (shortcut = “F5”) and adjusting the time. A reasonable evening time is acceptable. As you click on various dots in the sky (almost all of which are stars), a cross hair appears over your selected star, and information about the star appears in the upper left-hand corner of the screen. There's a lot of information here, including, on the first line, the various names of the star. The first name listed in that top line is the common name of the star. You should not be surprised that all bright stars or objects have a common name as they have been seen for millennia. Let's start with those names. Find the three brightest stars in the sky (the three biggest dots) and click on them one at a time.

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• What are your three stars’ common names? 1. _________ 2. __________ 3. __________

Near the bottom of each star's information listing, the distance to the star is listed, in light years (a light year is the distance light travels in one year).

• What are the distances to your three stars? 1. __________ 2. __________ 3. __________ You might recognize some of these stars. Each of these stars is part of a specific constellation, or area of the sky assigned to a particular mythical character, object or animal. To see the stick figure outlines of the constellations click on the Constellation Lines button in the bottom icon bar (shortcut key=”c”). Lines appear connecting the brightest stars in each constellation. To show the names of the constellations, click on the Constellation Labels button (shortcut key=”v”). Many of these constellation names should also be familiar.

• Name the three constellations that contain your three stars: 1: _________________ 2: _________________ 3: _________________

As you can see, it’s hard to tell where in the sky one constellation ends and the next one begins. To see the official borders between constellations, go to Sky and viewing option window on the left-hand side icon bar, then to the Markings tab, then check Show boundaries (shortcut key=”b”). The constellations' boundaries appear as red dashed lines. These borders are arbitrary, kind of like the borders between states – but astronomers have agreed to define them precisely, so that every spot in the sky (and hence every star) is in exactly one constellation. The IAU now defines “constellation” as grouping of stars within a sky region marked by the constellation boundary lines. See Wikikpedia for information (http://en.wikipedia.org/wiki/Constellation). To see pictures of the mythical characters associated with each constellation, click on the Constellation Art button (shortcut key=”r”) in the bottom icon bar. (It may be easier to see the constellations if you zoom in or out and drag the sky around to re-center it). The associated group of stars with the mythology is referred to as an asterism and is not the same as the constellation, explained above as all stars in an entire region. What constellation is just above the Southern horizon at “Current Time” tonight? What about Northern? To see constellation better, you may want to hide the ground using the “Ground” button at the bottom icon bar (shortcut key=”g”). Southern:______________________; Northern: ______________________ What constellation is at the Zenith at “Current Time” tonight? ___________________ How many constellations are in the sky at “Current Time” tonight? (count them!) _________ Open the Search window (CTRL-F or F3, or FN-F3 in some) to help you find the following

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objects. Remember, once you've typed the name of an object in the Search window, hit Enter and that object will be centered on the screen. If the Earth hides the object, then hide the ground.

• Find the constellation Ursa Major. Name two stars it contains. (Remember, click on a

star to see its name.) 1: __________________ 2: ____________________

• Find the star Rastaban. What constellation is it in? _____________________________

• Find the star Arcturus. How far away is Arcturus? _____________________________

Display the labels of the planets and the bright stars by pressing the Planets Labels button in the bottom bar (shortcut key = “p”). If you don't see any planets labeled on screen, open the View window and, in the Sky sub menu, make sure there is a check mark next to the Show Planets box in the Planets and Satellites section. Close the View window. Zoom back out to see the whole sky. Make sure that the constellation lines, labels and boundaries are displayed.

• Is the Moon out right now? If so, what constellation is it in? ___________ Set the time for 1 PM today, or 13:00 on 24H clock (press F5 or use the left-hand side icon bar). Again, make sure that you can see the whole sky by zooming out and dragging the sky around.

• Find the Sun. What Constellation is it in? ____________________________________

Now let’s see what the sky looked like at “Current Time”. Enter this time and date in the Date/Time window. Find the Moon in the sky and center it. If you do not see the Moon, then think a little and ask WHAT could be hiding it?

• What bright, named star is the Moon near? ________

• What constellation is this star in?

• What constellation is the moon in on next day? (NOTE: Rather than re-entering the new

date information each time, you can simply press the “=” key to advance the sky by one day)

• What constellation is the Moon in on the day after next day?

• What about one more day later?

Note that the Moon jumps around in the sky from night to night!

• (Bonus) What explanation can you come up with for this motion? _______________________________________________________________________ _______________________________________________________________________

There are many things to see in the sky besides stars, including planets, comets, asteroids,

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galaxies, nebulae, star clusters, and much more! The last three objects are called Deep Sky Objects. Each of these is a distant object much bigger than a single star and (almost) permanently located at a certain spot in the sky, in a particular constellation. There are many catalogs of Deep Sky Objects, most of which were published in the 18th or 19th centuries, including the NGC catalog (the New General Catalog), the Messier catalog (or the M Catalog named after French astronomer Charles Messier), and the IC catalog (the Index Catalog).

Stellarium uses the NGC, IC and the M catalogs. To show the labels in the sky for the brightest and most famous of these Deep Sky objects, press the Nebula button in the toolbar at the bottom of the screen, or simply press the N key. The brightest NGC/IC/Messier objects are labeled in the sky. Use the Search window (remember, you can access it simply by pressing the F3 key) to find and select the Deep Sky Objects below. You may have to zoom in or out to see them and their locations more clearly. If the object is below the horizon right now, press “G” to make the ground disappear. Again, information about the objects appears in the upper left-hand corner of the screen. The Messier number label, if available, would be next to the common name.

• What constellation is the Dumbbell Nebula in? _________What is its M number? ____

• What constellation is the Trifid Nebula in? ____________What is its NGC number? ___________

• What constellation is the Ring Nebula in? _____________What is its M number? _____

• What constellation is the Pleiades in? ________________________________________

• What constellation is the Triangulum Galaxy in? ______________________________

Add a Glossary here (To be done after Spring, 2017)

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PART B: Star Naming Methods There have been numerous methods devised over the centuries to identify stars. The oldest and most obvious way is to simply give the stars names. Many of these names have been around for centuries, and many came down to us from the Arabs, who were the world's best astronomers during the Dark Ages, when Western knowledge was almost wiped out after the fall of Rome.

Reset the Date & Time to the current time by pressing shortcut key “8”, or by using the Date/Time window. Turn the ground on if it is off (shortcut key= “g”), and turn the atmosphere off (shortcut key=”a”). Make sure the stars' names are displayed by opening the Sky and Viewing option window on the left icon bar and putting a check mark next to Stars in the Labels and Markers section of the Sky sub-menu. Before you close the option window, drag the slider next to Stars to about halfway to the right. What this does is that stars of certain level of brightness according to the slider scale will become visible. Close the Sky and viewing options window.

• Pick your three favorite common names from all the named stars you see: 1. _________________________ 2. _________________________ 3. _________________________

The problem with naming the stars is that there are FAR more stars than names, and people around the world can’t even agree on the names that exist! There have been several other, more scientifically precise methods devised to identify stars. The Bayer method, created by German astronomer Johann Bayer in 1603, labels the stars in a given constellation using the Greek alphabet, with roughly the brightest star in that constellation called α, after the first letter in the Greek alphabet (for example, α Orion or α Ori for short). The second brightest star is then called β, the third brightest γ, and so on, in the order of the Greek alphabet, which is… α, β, γ, δ, ε, ζ, η, θ, ι, κ, λ, µ, ν, ξ, ο, π, ρ, σ, τ, υ, φ, χ, ψ, ω

In English, these letters are written alpha, beta, gamma, delta, epsilon, zeta, eta, theta, iota, kappa, lambda, mu, nu, xi, omicron, pi, rho, sigma, tau, upsilon, phi, chi, psi, and omega. The Bayer method is still in use today, but even it can’t account for all of the millions of stars in the sky! In the 19th and 20th centuries, various exhaustive catalogs of many hundreds of thousands of stars were made, including the BSC or Bright Star Catalog, the HD or Henry Draper Catalog, and the HIP or Hipparcos catalog, which Stellarium uses. These catalogs simply number stars. For example, Sirius, the brightest star in the sky, is also known as α Canis Major, or HD 48915 or HIP 32349. In Stellarium, a star’s Bayer name is displayed in parentheses next to its common name. The star's Hipparcos (HIP) catalog number is listed after the Bayer name.

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• What are the Bayer and HIP designations for each of the stars you wrote down above? a. Star name: Bayer letter: HIP Number: _______ b. Star name: Bayer letter: HIP Number: _______ c. Star name: Bayer letter: HIP Number: _______

• What are the Bayer & HIP designations for the star Kocab or Kochab (in the

constellation Ursa Minor)? (Use the Search window to find it) Bayer: _______________ HIP: ________________

• What is the common name for the star α (alpha) Ursa Major, also known as α UMa ?

(Use the Search window to find Ursa Major, then zoom in and click on the bright stars in Ursa Major until you find it) ______________________________________________

• What is the common name for γ (Gamma) Draco or γ Dra? ______________________

PART C: Star and Constellation Movement Now that we are able to identify stars and constellations, let’s look at how they move over time.

Zoom out to show the whole sky and center it on the screen, with North at the top of the screen. Press the Increase Time Speed button three times on the bottom tool bar and watch the stars move. Remember, you can also do this by pressing the L button on the keyboard three times. Each time you press the button, time goes 10 times faster, so three clicks makes time go 1,000 times faster than normal!

• Which way do the stars move as time passes? (W to E? E to W? N to S? S to N?) _____

• Find the only star that’s not moving. Click on it. What is its name? ____________

• (Optional) Why do stars move the way they do? _________________________________ ________________________________________________________________________

Display the constellations and their boundaries as you did before (press C, V, and B). As you watch time pass 1,000 times faster than normal, can you find the one constellation that never sets below the horizon– in other words, it cam always be seem in the sky from the given “Current Location”, no matter what time it is? We call a star or constellation that never sets circumpolar.

• Find one completely circumpolar constellation (in Current Location)?

_______________. Is it the only one? _______________

Press the Set Normal Time Rate button to let time pass normally. You can also do this by pressing the K button your keyboard.

Change your location to the North Pole by opening the Location window and clicking on the

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very top edge of the Earth map. Your latitude should change to 90° North – the North Pole! Don't worry if you're not exactly at the North Pole – just try to get the Latitude to as close as 90° North as possible. Close the Location window. Now press L three times again to make time pass quickly.

• What do the stars do now? ________________________________________________

• Now where in the sky is the star that doesn't move? _____________________________

• (Bonus) Does this make sense? Explain. _______________________________________ _______________________________________________________________________

Press K, and then set the location for Singapore (open the Location window, enter Singapore in the Search box, and then click on Singapore, Singapore), which is almost exactly on the Equator (Latitude = 0°). Close the Location window. To see the horizon more easily, click on the Sky and Viewing Options icon to open the View window, click on Landscape on the top to open the Landscape sub-menu, and then click on Ocean. Close the View window. Finally, press L three times to make time run 1,000 times faster than normal.

• What do the stars do now?

• Now where in the sky is the star that doesn't move?

• (Bonus) Does this make sense? Explain. Press K to make time run normally. Reset the location to “Current Location”, and set the time for 12 Noon on today’s date. Press L three times again and watch the Sun move.

• Does the Sun move along with the stars?

• How about the Moon (if it’s visible)? Does it move along with the stars? You now know how stars are named, how they are arranged, and how they move as the hours pass. You’re well on your way to becoming an astronomer!

PART D: Messier Objects

Background: Charles Messier charted 103 deep-sky objects during his observing career. Deep sky objects are non-stellar objects such as galaxies, nebulae, open star clusters, globular star clusters, and other objects that are beyond the solar system. Use the following 5 Messier objects – M1 plus 4 more selected by your instructor. Use “Find” option, type in the corresponding label such as M1 or M15 and press enter. Zoom in on the object using the scroll-wheel on the mouse or the +/- keys until the image of the object appears. You may need to turn off the atmosphere effect to darken the sky. Use the info pane or go to

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www.wikipedia.com for information if needed. M object for all: M31 M objects via instructor’s choice: M1, M13, M45, M57 (Suggestion for additional questions: NGC designation? Which constellation? Nearby bright star? Where is the sun/moon? TBD in Spring, 2015)

Fill in blanks below each M object number or label in the order shown above.

1. M_31__ i. What is the common name? ____________________ ii. What kind of object is it? __Galaxy (but designated as a “Nebula” prior to 1930’s)

2. M___

i. What is the common name? _____________________ ii. What kind of object is it? _______________________

3. M___ i. What is the common name? ______________________ ii. What kind of object is it?________________________

4. M___

i. What is the common name? ______________________ ii. What kind of object is it? _______________________

5. M___

i. What is the common name? ______________________ ii. What kind of object is it? ________________________

Write a brief conclusion summarizing your results and what you learned in this assignment. Suggestions and comments to improve the lab are highly appreciated. ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Glossary: (This is to be completed at a later time)

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SupplementalInformationhttp://www.stellarium.org/wiki/index.php/Keyboard_actions This lab is written by Mike Chu, with contributions from Jeff Cronkhite, Andrew Patrichuk, and ASTR101 students. Subsequent Labs with Stellarium

1. Sky Coordinates 2. Position of the Sunset and Sunrise 3. Motion of the Planets 4. Parallax and Distance Measurements to the Moon