CL - Introduction (remote) (1)

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California State University, Bakersfield *

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Apr 3, 2024

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Computer Lab – Introduction (Virtual Lab Remote Edition) A “Voyager Introduction Video” (created by Dr. Krishna Prasai of the CSUB Physics and Engineering department) is available on Canvas. Launching the Program Using a desktop or laptop computer, use the “VCL” (Virtual Computer Lab) link in the sidebar of the class site on Canvas. Alternatively, you can navigate in a browser to csub.apporto.com and log in with your CSUB credentials (you won’t have to log in if using the Canvas link). Click “Launch” to start the Voyager 4 application. Click the square button in the title bar to expand the Voyager program to fill the window. Either use these instructions on your computer side-by-side with the Voyager program or run the instructions on a different device. Write out all your values and answers, turn in the final lab report as directed by your lab instructor. [Need help? See the end of the lab for help contact information.] The Voyager Screen You should see a large window titled "Sky Chart" and a smaller window (the "Time Panel") with just "Time" as its label. The Time Panel is used to set the time and to control animations. Near the bottom of the Chart window is a line of data including the local mean time (LMT) and the viewing location (which has been set to default to Bakersfield). Below that are some controls – zoom controls, projection types, lock, and a horizontal scroll bar. Along the right edge of the window, near the top, is another column of control buttons. The bottom button is the labels display button (it has "ABC" written on it), it controls whether labels (names) of objects will be shown on screen. That button is currently selected, click it once to turn off the labels (you may see some vanish from the screen), then click it again to turn the labels on again. (Dark button background when turned on, light when turned off.) The Chart window is showing a large piece of the current outside sky. The program can display just a small part of the sky (like you might see through a powerful telescope) or show a huge portion of the sky (even more than you could see at any single moment with your naked eye). The program can display stars, planets, galaxies, comets, asteroids, and more. It can show what the sky looks like from any place on Earth at any time in the past or future. It can display the view from other planets or from any point in space. And it can animate the display to show how the view changes as seconds, days, years, or centuries pass. Each dot represents a star. As you move the cursor to point at stars, their names should pop up on the screen. Centering a star in the cross hairs and pressing the left mouse button will bring up the "Info Panel" for that star with information about the star you selected. Most of the information displayed is pretty technical, don’t worry about it. Close the Info Panel by clicking the small "x" at the far right of the Info Panel's title bar – make sure you don't close the Time Panel or Chart window. A common mistake is to click within the window while moving the cursor. This can select a tiny rectangular region of the window and “zoom” in to show that region (which will probably just show 1

up as an empty black window). If that happens, click on the zoom pop-up menu (bottom-left corner of the window, in the picture above that menu is labeled “120° x 55.6°”) and select 120°. There may also be some colored symbols visible in the Chart window, these represent the Sun, Moon, and planets. You can click on any of these and get information just like with the stars. Try it! Using Menus Close the Info Panel if open. Voyager has a number of options for how the sky is displayed, these are mostly accessed through menus. The menu bar is the row of words at the top of the window. To use a menu, point the cursor at the menu name using the mouse. We are going to select a particular option from the "Center" menu. Use the mouse to point the cursor at the word "Center", press and hold down the mouse button. From the menu that appears, move the cursor until pointing at the word "Direction". While still holding down the mouse button, select "West" from the additional menu that appeared. Now let up on the mouse button and the menu selection will be made. If you let up on the mouse button early or moved the mouse out of the menu area, you'll have to start over. When done correctly, the Chart window should appear half green/half black, and the due west direction will be at the center of the screen (but that will likely not be obvious). In the future, we'll refer to this menu selection by saying: "Select the Center/Direction/West menu". Got that? A Simple Animation We are going to animate the sky. Look in the Time Panel, see where it says, "1 day"? This is actually another type of menu, a "pop-up menu". Click where it says "1 day" and select "1 min" from the menu that appears. We have just set the "Time Step" to be one minute. Click on the "Start" button in the Time Panel, this starts the animation of the sky. We are seeing a movie of the western sky where each frame of the movie is one minute later than the previous frame. You can stop the animation by pushing the button that now says "Stop" in the Time Panel but let the animation continue, at least for a little while. If you stand outside and look west, you can see a large portion of the sky. But your view of the sky below eye level is blocked by the ground. The boundary between where the ground ends and the sky begins is called the horizon. On the Voyager screen, the ground is indicated by green, anything "in the green" will be below the horizon and not visible outside. Like in real life, you'll often see hills and trees along the horizon on the Voyager screen. It takes some getting used to, but the small display the screen is showing is a huge area of the sky. You should see time rapidly changing in the Time Panel. As the day goes on, the stars and planets are setting in the west. The Sun and planets move across the screen at a slightly different speeds, just like they do in the sky. The Sun always moves slower across the sky than the stars, but you probably won't be able to notice that with this slow-paced animation. Stop the animation. Setting Location 2

Select the Chart/Set Location… menu (no sub-menu this time). A picture of the Earth’s globe appears with various city names written atop it. You are going to set the viewing location to where you were born, go through this process even if you were born in Bakersfield. The Earth globe is currently centered on California, if you were born in a different part of the world, you can spin the globe by using the scroll bars sitting next to the map. When the globe is centered approximately correct, click several times on the small "+" button just below the Earth-map area. As you continue to click this button, you'll see more and more city names popping into view. Use the scroll bars to further shift the map as needed. [Be aware that the streamed version of Voyager 4 is often slow to respond to clicks and may have difficulty detecting double-clicks.] Again, the goal is to select the location where you were born. Wherever you click, that location becomes selected, you'll see the location marker on the map move and the listed longitude and latitude values change. If you click on a white dot, that city will be selected. You might also be able to set your birth city by finding and selecting it from the city list along the left side. You don’t have to select a white-dot location, you can click on any spot. You don't have to type in a name for the city – the program pays no attention to the name – but it might make things clearer for you. Once you’ve selected your birthplace, click the button labeled “OK” or hit the Enter key on your keyboard. Now that we’ve set the place of birth, we’ll set the date. Setting Date and Time The Voyager lab instructions often have long sections of “cookbook” steps, you need to be meticulous in following those steps. Skipping a single step can result in a mess and force you to go back and restart a long section. If you do get into a situation where everything is so messed up that you need to restart, you can reset the Voyager program to the settings it had when you first launched the program by selecting the File/Open Recent Settings/Startup.vgr menu. Select the Chart/Set Time… menu. The Local Mean Time being displayed is the program time when you stopped the previous animation. By hitting the Tab key twice, the year value should appear selected, you can now type in your birth year and it will replace the year currently shown. Push the Tab key again and then enter your month of birth (you can use the month number; 1 for Jan., 2 for Feb., etc.). Enter the day of birth as well. You can go backwards through the fields by pressing Shift-Tab or use a mouse to select any field you wish to change. You don't need to change the Time, you can leave Automatic Daylight Savings Time selected. When you have your correct birth date, click OK or hit Enter. You should now see your birth date listed in the Time Panel. Display Controls At the bottom of the Sky Chart window is a pop-up menu that currently says "Altazimuth" (if you just see some gray boxes, click once within the Sky Chart window to activate it). Select "Equatorial" from that menu. This changes the view to a "star atlas" view, just displaying the celestial sphere 3

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ignoring any restrictions on our view due to the ground and not showing any motion of stars due to the rotation of Earth. Select the Display/Constellations… menu and select "Zodiacal Constellations" from the Display pop-up menu. Click the box next to "Show Constellation Labels" to turn that on. Click the tab near the top of this window that says "Boundaries and Regions". Click to turn on the "Show Boundaries" option and also turn on the “Use Thick Lines” option, then click the OK button. Now we will have the names of the zodiac constellations displayed as well as exact boundaries telling us where one constellation ends and another begins. Astrology Astrology is the belief that the positions of the Sun and Planets at the time of your birth dictate your future. An astrological forecast involves figuring out where each planet was when you were born (which constellation, or "house", each was in) and interpreting that pattern. We have just achieved the first part; the computer screen is now showing where all the planets were on your day of birth. Scroll Bars You can only see a limited portion of the sky on the screen, and that may not even include any planets. Experiment with the scroll bar controls; you can click and drag the scroll box, use the scroll arrows at the end of the scroll bar, or click in the open areas next to the scroll box. The scroll bar is like turning your head to look at a new part of the sky. There is also a vertical scroll bar along the right-hand side of the screen, this shifts your view up and down. A scroll wheel on your mouse might control the vertical scroll bar. Another way to shift your view is to double-click within the Chart window. The spot where you double-click will become centered. An alternate way to shift your view is to hold down the spacebar and click-and-drag within the main window. Careful, those last two methods are easy flub and you may end up selecting a small rectangle and zooming in to that small region. Not seeing any labels? Make sure the “ABC” button is on and that you haven’t scrolled too far up or down. Determine the constellation that the Sun, Moon, and planets were in on the day you were born. This picture shows Venus within the constellation of Capricorn (Venus on your birthday was likely in some different constellation). Fill in the table: (Do it!) Object Constellation Object Constellation Sun ______________ Saturn _____________ Mercury ______________ Uranus _____________ Venus ______________ Neptune _____________ Mars ______________ Pluto _____________ Jupiter ______________ Moon _____________ 4

Most of the constellations will be the familiar ones that make up the “zodiac”. If a planet looks like it's right on the border between two constellations; (1) double-click near its icon in the Chart window, (2) select 10° from the zoom pop-up menu (at the bottom left), (3) zoom back to 150° after deciding on which constellation. A planet that cannot be found may be ‘hiding’ behind the Sun or Moon, or its label may be missing because it overlapped with a constellation label. If you can't find a planet, select the Center/Planets/Planet Name menu to find a lost planet. Sometimes a planet will not be within any of the zodiac constellations. It will still be within some constellation; the entire sky is mapped into 88 constellations with no gaps between them. One way to find out which one is to click on the planet’s icon to get its Info Panel, then click on the Visibility tab and look where it says, “In Constellation:”. Got them all? Select the Tools/Planet Report... menu. You’ll probably see the words "Heliocentric Positions" near the upper left of the window (probably hiding behind the Time Panel). That is a pop-up menu. Select “Equatorial Positions” from that menu. The middle column in this table indicates the constellation each planet is in; check that this agrees with your answers above. If it doesn't agree, it is probably the Planet Report that's wrong, not you; the program only lists the approximate constellation in this window. When done, click on the close box to remove the Planet Report window (the small x button, be careful not to close the Voyager 4 program by clicking the large X button above it). Your astrological sign, what you look up in the newspaper (if you waste time with such things), is the constellation the Sun was in when you were born. Note that this constellation is not visible at this time – it sets when the Sun sets. The best time to see ‘your’ constellation is in the evening sky several months before your birthday Zodiac and Precession Again, your 'sign' is the constellation you wrote for the Sun on the previous page. Your sign is probably not the astrological sign you thought you had. What’s going on? [Parts of the following discussion are adapted from the article “What’s Your Sign” by David Hasenauer, Sky & Telescope June 1998.] Historically, the Sun was considered to pass through 12 constellations (the zodiac) spending about 30 days in each. But the Sun’s real path (the ‘ecliptic’) passes through 13 constellations (the 13th is Ophiuchus – the Serpent Bearer) and spends unequal time in each due to the varying sizes and locations of the constellations. Each year the Sun spends 45 days in Virgo but only six days within the boundary of Scorpius (true “Scorpios” are uncommon). It gets worse, the correspondence between dates and Sun-signs was decided about 2000 years ago (largely by Ptolemy). Because of an effect called precession (due to a slow wobble of the rotating Earth, one full wobble every 25,800 years), the dates on which the Sun is in a particular constellation slowly shift. On June 1 st , 2000 years ago, the Sun was in Gemini, today on June 1 the Sun is in Taurus. Here’s another way to look at it. Our calendar (the Gregorian calendar) is based on the tropical year – the cycle of the seasons. The time for the Sun to return to exactly the same location in a constellation is the sidereal year (the time for Earth to make one orbit around the Sun). Because of precession, these years are not exactly the same, they differ in length by about 20 minutes. So, a date that just barely qualified as Aries by 10 minutes this year, might be Pisces next year. The following table summarizes the situation: Constellation Traditional Dates Actual Dates* Days Capricorn Dec 22 - Jan 21 Jan 21 - Feb 16 26 5

Aquarius Jan 22 - Feb 21 Feb 16 - Mar 11 24 Pisces Feb 22 - Mar 21 Mar 11 - Apr 18 38 Aries Mar 22 - Apr 21 Apr 18 - May 13 25 Taurus Apr 22 - May 21 May 13 - June 22 40 Gemini May 22 - June 21 June 22 -July 21 29 Cancer June 22 - July 21 July 21 - Aug 10 20 Leo July 22 - Aug 21 Aug 10 - Sept 16 37 Virgo Aug 22 - Sept 21 Sept 16 - Oct 31 45 Libra Sept 22 - Oct 21 Oct 31 - Nov 23 23 Scorpio Oct 22 - Nov 21 Nov 23 - Nov 29 6 Ophiuchus –––––––––– Nov 29 - Dec 18 19 Sagittarius Nov 22 - Dec 21 Dec 18 - Jan 21 34 *For the year 2000, dates shift one day later every 70 years due to precession. Astrological Forecasts "When the Moon is in the 7 th house And Jupiter aligns with Mars Then peace will guide the planets And love will steer the stars. This is the dawning of the Age of Aquarius – The Fifth Dimension (1969) We are in the "Age of Pisces" currently. Why? Because the vernal equinox (the Sun's position in the sky on the spring equinox) is in the constellation Pisces. Because of precession, the constellation behind the Sun slowly shifts (the same shifting we just learned about for people's astrological signs). But the shift is slow, the Age of Aquarius with the song's promise of peace and love, won't be here for nearly 600 years. Although you found which constellation each planet was in when you were born, there is more than that involved in making astrological forecasts. The zodiacal constellation rising in the east at the moment of your birth is your "ascendant". The ascendant is your first house, the next constellation to rise is your second house, and so on. So, each planet will be in a numbered house. Astrologers then analyze pairs of planets. Two planets six houses apart is considered very bad, four houses apart is very good, three houses apart is pretty bad, two houses apart is pretty good. Conjunctions (close pairings) also have special meanings as do each of the houses. Why is six houses different bad and four houses good? Why is it the moment of birth that determines all your characteristics rather than, say, the moment of conception (which biologists tell us is when all your genetic code is determined)? Although it is all rather complex and detailed, scientific tests have never shown any aspect of astrology to predict or explain human behaviors. Sunrise & Sunset Find the Sun and click on it once to bring up its Info Panel. Click on the "Visibility" tab within the Info Panel. Record the Rise and Set times for the Sun below. Sunrise: _________________ Sunset: _________________ 6

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On any other day of the year, the rise and set times would be different. Select the Chart/Set Time… menu, change the year to this year (don’t change the day or month) and click OK. The rise and set times should be the same (or maybe one minute different depending on leap-years). Close the Info Panel. Long-Term Motions Change the Time Step (the pop-up menu in the Time Panel that you set earlier to 1 min) back to 1 day. Start the animation. The resulting picture shows the motions of the planets relative to the stars. The Sun follows a simple circular path called the ecliptic (we are looking at less than half the sky, the circles are completed off screen). The Sun makes a complete circle in one year – the Sun will rise and set 365 times during that year but moves across our sky slightly slower than the stars so that after a year it is back with the same stars. The Moon’s path is also pretty simple although it zips by so fast it’s hard to tell. Watch how Mercury (and Venus to a lesser extent) never gets far from the Sun, you can see it going around the Sun. It’s not as obvious that the other planets are orbiting the Sun, that’s because we are viewing from the Earth that is itself moving around the Sun. All the planets have periods when they briefly go backwards (called “retrograde”) compared to their usual direction of motion across the celestial sphere. The planets always rise in the east and set in the west, they just vary in the speed that they go across the sky. Planets going slower than the stars move from right to left on the screen, planets going faster (retrograde) move left to right on the screen. Q. Which object moves fastest compared to the stars? A. That's easy, it's the Moon. Q. How long does it take the Moon to make one orbit of the celestial sphere? A. About one month, maybe a little less. Q. Why does the textbook say the Moon goes around our sky in 24 hours and 50 minutes? A. It does! Both the Moon and stars cross our sky from east to west every day, the computer is currently just showing the pattern of stars and not their daily motion (we watched that motion earlier with the western horizon and 1-minute time steps). The Sun and planets move around our sky at almost the same rate as the stars, so they move only slowly compared to the stars. The Moon moves much slower than the stars which is why it is moving through the constellations so fast on screen. Click Stop to end the animation. View from Space With the Voyager 4 program, you can view from anywhere in the solar system. Select the Window/Location Panel menu then click on the Solar System tab. By dragging the arrows or using the increase/decrease controls, set the Ecliptic Longitude to 0 (zero), Ecliptic Latitude to 90°, and Distance (from Sun) to 10. You can close the Location Panel. Select the Window/Planet Panel menu. Double-click on the Sun button, this centers the Sun in the Chart window. Click the "Name" button – make sure the names are turned on for all the planets (an "X" for 7

each). Turn off the Moon (white background for name when off). Click the "Orbit" button to turn that on for all the planets, then close the Planet Panel. Select 30° from the zoom pop-up menu at the bottom of the screen (Make sure to select 30° and not 30” or 30’). With the Time Step at 1 day, Start the animation. This is a view never experienced by man. We are watching the inner planets orbiting the Sun. Note that Mercury’s orbit is clearly not a circle and the Sun is off-center. Mercury’s distance from the Sun varies substantially, you should be able to see that it slows down when it is further from the Sun. Mars too has a distinctly non-circular orbit. Demo Files It is possible to save the program settings to a computer file so that they can be retrieved at a later time. Many such “Settings Files” or “Demos” have been created for the Voyager 4 program and we will use many of them during the quarter. Today we will examine some Demo files which recreate interest- ing historical events and some that give a taste of the capabilities of the program. Select the File/Open Settings... menu. The Setting Files for the program are stored in a folder (called "110 Settings", 110 being the previous number for the astronomy class before it became 1609) that is within the Voyager 4 folder. The first time you open a Settings File you must navigate through this sequence: This PC, Program Files, Carina Software, Voyager 4, 110 Settings, Sometimes the default location after doing the Open Settings command is a weird “System32” folder instead of the top level “This PC”. If that happens, click the “ ≪ ” symbol to the left of “Windows”, then click on “Local Disk (C:)” followed by “Program Files” etc. Within the 110 Settings folder, select and open the file called "Christmas Star". Most Settings Files have a short description that you should read first. You are seeing Venus and Jupiter looking like one brilliant object as seen from Babylon in the year 2 BC. The stunning terrain shown is not actually that of Babylon but is one of the seven horizon images that come with the program (this one is "Desert Road"). Answer the following questions: (some answers to questions appear at the end of the lab) 1. This demo uses Voyager's "Natural Sky" option, few stars can be seen because the Sun has just set, you can still see the Sun's glow along the horizon. What is the local time for this displayed sky? 8

2. Is Venus actually eclipsing our view of Jupiter? We can use the Voyager program like a telescope to find out. Click repeatedly on the zoom "+" button (the zoom menu is near the bottom left of the window and is actually labeled something like "116° x 88°", that being the current angular size of the sky being viewed, the "+" button is next to the zoom pop-up menu and pressing it narrows the amount of sky being currently viewed). Is Venus eclipsing our view of Jupiter? Click the Start button in the Time Panel to view the changing positions over time. Your view will go dark/blurry after a bit, that's because Jupiter and Venus have set, and you are seeing a close-up view of the terrain. Click the Stop button in the Time Panel. The Greek philosopher Aristotle observed an occultation (eclipse) of Mars by the Moon on May 4, 357 BC. The Moon was near first quarter on that date. Aristotle recorded that Mars disappeared behind the dark side of the Moon and then reappeared on the bright side. He correctly concluded that the Moon is closer to the Earth than Mars. Again, select the File/Open Settings… menu, this time open the Settings File called "Mars Occultation". [You only have to navigate through that folder sequence the first time you open a Settings File in each session.] 3. At about what time does Mars disappear and reappear? You can make the animation run forward or backward using the right-pointing or left-pointing arrow buttons near the Start button on the Time Panel. The buttons just inside those, flanking the Start button, allow you to advance time forward or backward in single steps (which is the best choice for viewing this). You may also want to zoom further in for a clearer view. Disappears:____________ Reappears:____________ That was interesting but we didn't get much of a view of Mars. So, select the File/Open Settings… menu and open the file called "Mars Closeup". You may be seeing mostly the dark side of Mars, if so, that can be fixed using the arrow below "Ecliptic Longitude" in the Location Panel. Click on the arrow and hold the button down while you drag the arrow around to the other side of the circle. You should now see a big, beautiful picture of Mars. The white area near the top is the north pole ice cap, a combination of water and carbon dioxide ices. The long, horizontal scar near the bottom is Valles Marineris, a trench or valley that is as long as the U.S. is wide. Click "Start" in the Time Panel and you'll see a line of three blemishes rotate into view. Those are three colossal volcanoes. Left of those three is a larger blemish, Olympus Mons, the largest mountain in the entire solar system (it too is a volcano). 4. Click near the center of Mars to get its Info Panel, click on the Physical tab. What is the mass of Mars compared to Earth? Select the Tools/Image Gallery… menu (then close any of the panels from the previous demo that are blocking your view). Select "The Solar System" for the left pop-up menu (may already be selected) and "Europa" for the right pop-up menu. Europa is one of Jupiter’s four 9

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large moons, one of the four moons first discovered by Galileo, hence the quartet are often called the “Galilean Satellites”. Unfortunately, for some reason, this streamed version of the Voyager 4 program does not display pictures correctly at full size. So, don’t click on the pictures, we’ll just look at the smaller pictures in the gallery. Look at the first, B078, picture. The moon Europa is covered by a thick layer of ice, the crisscrossing lines on the surface are cracks in the ice. Below the ice is believed to be a liquid ocean that many scientists think may harbor life. Look at the other pictures of. Change the menu from Europa to Io (another moon of Jupiter, the name is pronounced “eye-oh”). Picture X032 (number 4) is a nice close-up of Io. Io, because it orbits very close to Jupiter, has its interior melted and boiled by tidal forces from Jupiter. The surface of Io is littered with constantly erupting volcanoes and the moon is blanketed with sulfuric lava flows. Picture D073 (#19) is a great picture of Pele, Io's most famous volcano. Picture H595 (#2) shows the four Galilean Satellites in order of decreasing size (Ganymede, Callisto, Io, Europa); of the four, Io is closest to Jupiter followed by Europa, Ganymede, and Callisto. In the Image Gallery, select Jupiter. Many of the pictures show Jupiter in 1994 after being hit by the Shoemaker-Levy 9 comet, such as X020 (#14). The comet had broken into pieces in an earlier close encounter with Jupiter and the fragments all crashed into Jupiter. The impacts left the temporary dark spots seen in the pictures. Change "Jupiter" to "Moon" in the Picture Gallery. Look at those pictures. Then look at the spectacular Saturn pictures. Wow, and there's still hundreds more pictures available. Change "The Solar System" to "Clusters and Nebulae", enjoy the pictures. Open the Settings File "Mercury Transit", you may have to zoom in more to see Mercury. Start the animation, stop when Mercury is about half-way across the Sun. This gives you some indication of how much larger the Sun is than Mercury. In fact, because Mercury is closer to us in this view, it appears almost twice as large as it would if at the same distance as the Sun. Click on Mercury to get its Info Panel, click on the Pictures tab. Click on the "Mercury Mosaic" picture to see what Mercury looks like up close – it looks a lot like our Moon. These pictures were taken by the Mariner 10 spacecraft; Voyager does not contain the more recent pictures by the MESSENGER spacecraft. 5. How long does it take Mercury to orbit the Sun? [Check under the Orbit tab.] 6. How come a transit of Jupiter has never been seen? Hint: A planet must be between the Earth and Sun for us to see it "transit" the Sun. Open the Settings File "Saturn and 28 Sgr", read the Settings File Info. The star 28 Sgr is a red giant star well over a thousand light years away and is barely visible from Earth. Nevertheless, it is rare that Saturn's path across the sky intersects even a modest star like this. Because the star passed behind Saturn's rings, it flickered in brightness as more or less starlight was blocked by particles in the rings. The pattern of the flickering gave crucial information about the variation in density of Saturn's rings. Change the Time Step to 30 sec, start the animation, stop after 28 Sgr has passed all the rings. 7. What are the things labeled Dione, Tethys, Rhea, Enceladus, and Mimas that appear on screen? 10

Open the Settings File "Mars and Jupiter in 1591", read the Settings File Info. Animate, stop after Mars has scooted by Jupiter. 8. What viewing location is being used for this demo? Hint: It is written on the screen, and no, it is not "Ecliptic", "Gnomonic", “LMT”, or "Jupiter". While Kepler was wrong in thinking that Mars had passed directly in front of Jupiter, such a thing can happen. Coincidentally, a few months earlier, on Oct. 13, 1590, the planet Venus did occult (eclipse) Mars as seen from Earth (but it wasn't visible from Kepler's location). Open the Setting File called "Mars and Venus in 1590". Start the animation to see Venus pass in front of Mars. 9. Would you characterize this as a total or partial eclipse? The Voyager 4 program can simulate some spacecraft journeys, like that of Voyager 1. Open the Setting File "Voyager 1 Jupiter flyby". Read the Info then Start the animation. 10. After Jupiter, Voyager 1 then went on to fly by the next planet out in the solar system, which planet is that? Open the Settings File "Northern Constellations", animate. This is a view from Bakersfield looking north. The cyan (light blue) circle indicates the boundary within which are all the circumpolar stars as seen from Bakersfield. See how those stars all move in circles, never dipping below the horizon. The bright star in the center is Polaris, it is at the end of the tail of the Little Bear (Ursa Minor), it is also the end star of the handle of the Little Dipper. Stop the animation, find the Big Dipper (it is in the constellation Ursa Major). 11. Are all the stars in the Big Dipper circumpolar? [Having trouble finding the Big Dipper? Here, this shows what it looks like on screen after advancing the time to 7:46 PM (Do you see it? The top four bright stars are the bowl of the Dipper with the stars below forming the bent handle.). In fact, you can answer this question just by looking at this picture. 12. What is the name of the end star of the handle of the Big Dipper? Hint: All you have to do is point the cursor at the star and its name should pop up. 13. How long does it take for the stars to make one complete circle in the sky? (Don’t try to answer this using the computer, you should have already learned the answer in class). Hint: The answer is not 24 hours. Open "Planet Paths" and animate. This is a view from Earth locked towards Mars. You will see planets (including Mars) do periodic retrograde motions. Most of the confusing motions are the result of viewing from the moving Earth. 11

14. Which planet leaves the trail of brown dots? Open the Setting File "Planet Motion from Space". This is a view from 40 astronomical units (forty times the Earth-Sun distance) above the Sun with the view zoomed in to show the inner planets. Animate. 15. Which planet completes an orbit fastest? Select 120° from the zoom pop-up menu at the lower-left (click where it says something like 8.00° x 5.89°). Select "3 months" for the Time Step in the Time Panel (click where it says "Step: 1 day"). Restart the animation if you stopped it. 16. Jupiter takes less time to complete an orbit than Neptune, but is that simply because it has a smaller orbit? Look closely and decide which is actually moving through space faster, or is it a tie? Multiple Choice: Jupiter moves faster // Neptune moves faster // Equally fast Open the file "Sky Zoom", you can explore just by scrolling around the screen and zooming in where things appear interesting, but we will do it a different way. Select the Center/Messier Objects… menu. Messier (pronounced MEZZ-ee-aa) Objects are celestial objects listed in a catalog published by Charles Messier in 1774. Click on each of the objects in the list below to see what they look like (just click on the object's name in the list, don't click the center button). Messier 1: The "Crab Nebula" is the remains of a star that exploded. Messier 13: You are seeing hundreds of thousands of stars clustered into a spherical region just 145 light-years across. Messier 31: The Andromeda Galaxy, a nearby galaxy of stars similar in size and shape to our Milky Way galaxy. Messier 42: The Orion Nebula is a nearby gas cloud actively condensing into new stars. Messier 45: A cluster of newly formed stars, what the Orion Nebula might look like in a few million years. Messier 51: A spiral galaxy seen face-on. Messier 57: A dying star that has ejected a ring of material. Want to see more? Help yourself! And by changing "Messier Objects" to "Caldwell Objects" or "Deep Sky Objects" you'll find hundreds more to see. We have barely scratched the surface of what the Voyager program can do. Feel free to play with the program. Don't be afraid to experiment, there is nothing you can do that will 'damage' the program. You can close the Voyager program by clicking the large X in its title bar; you can leave the Virtual Lab by closing the browser window or tab. Selected Answers: 1. 7:51:47 PM 4. 0.1074, about 1/10th as much. 6. Jupiter orbits further from the Sun than Earth. So, Jupiter can never move in-between the Earth and Sun and be seen in transit. 7. They are moons of Saturn. 8. Stuttgart (in Germany). This is close to Tuebingen where Kepler was living at the time. 12

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9. Partial 11. No (all the Big Dipper stars would have to be within the cyan circle to all be circumpolar). 13. 23 hours and 56 minutes 13

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