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Web Assignment:
Sky View Café and the Planets

Go to the following web page: http://www.skyviewcafe.com/. About two-thirds of the way down the page there is a link to “Use the Sky View Café interactive planetarium now.” Clicking on this link will cause a Java application to load. Set your location to Scarborough, Maine and save it.

You will be using the Sky View Café application to explore the motion of the planets around the Sun. First, you will use the Internet to define some key terms and to collect some information about one Solar System object. Second, you will examine the planets’ orbits from a point far above the Solar System using the Orbits tab. Finally, you will look at a few of the naked-eye-visible planets as they are seen from here on Earth using the Sky tab and the Ecliptic tab.

Part I: Planetary Information

First, define the following terms. Feel free to use Wikipedia, the Wikipedia Solar System page, or some other online source to find the meanings of these words:

  1. aphelion:
  2. perihelion:
  3. superior conjunction:
  4. inferior conjunction:
  5. greatest elongation:
  6. opposition
  7. (apparent) retrograde motion:
  8. astronomical unit (AU):
  1. eccentricity:
  2. orbital inclination:
  3. orbital period:
  4. rotational period:
  5. terrestrial planet:
  6. Jovian planet:
  7. dwarf planet:
  8. asteroid:

Next, choose one Inner Solar System terrestrial planet, one Outer Solar System gas giant, one minor planet or one major moon from anywhere in the Solar System. Use the list on Wikipedia found on the List of Solar System Objects page. Find the following information about your solar system object:

  1. aphelion and
    perihelion distances:
  2. length of day:
  3. length of year:
  4. eccentricity:
  1. mass:
  2. composition:
  3. size relative to earth:
  4. space probe visits (name & date):
  1. special features (find five that make it unique):
  2. Is life as we know it on Earth possible on the Solar System object you chose? Why or why not? What would it take to make it a place where we could live?
  3. What makes your Solar System object more interesting than any of the others?

Part II: Motion of the Planets in their Orbits

Go to the orbit tab of Sky View Café.

  1. Use the arrow keys to advance from the present moment by days (upper-left corner in the date-time box). (a) What direction do the planets orbit the Sun: Clockwise or counter-clockwise? (b) Do they all orbit the same way? Use the “Select an orientation” menu just above the view window to change the view to 180° (or drag the display). (c) What direction do they orbit now? (d) What did changing the orientation do?
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  2. Use the orientation menu to set the orientation to 90°. Set the Options menu to show out to Pluto. What is different about Pluto’s orbit compared to the other planets? Draw a picture.
  3. Set the orientation to 0.0° again and view out to Mars. Use the arrow keys to move forward by days again. Which planet moves fastest? Which one moves slowest? Based on this information, and without using Sky View Café, write down which moves faster around the Sun: Jupiter or Neptune.
  4. Use the “previous/next event” menus at the top of the screen to find the date of the next three oppositions of Mars. In the menu on the left choose Opposition and the menu on the right choose Mars. Then click the big blue arrows to the right or left to find upcoming and preceding events. Leave the date at one of the oppositions you find and set the time for 8 pm (20:00). Go to the Sky tab and try to find Mars during the night. Is it possible to see it at night at opposition? Try moving through the night by hours with the arrow keys. Draw a picture showing the Sun and the orbits and locations of Earth and Mars at an Opposition of Mars. Is Mars in the sky for an observer on the night side or the day side of Earth?




  5. Go to the Orbits tab. Set the date for 5/01/02 at 8:30 pm (20:30). Use the view options to look at the Solar System Out to Mars and then Out to Saturn. Do you notice anything interesting about the planets? What? Describe what you see and draw a sketch. Go to the Sky tab and set it to look due West using the Horizon to Zenith viewing option. A planetary alignment like this, called a Conjunction, will not happen again until July 2060. See http://en.wikipedia.org/wiki/Astronomical_conjunction#2002 to read about this conjunction and planetary conjunctions in general.
  6. Go to the Sky tab and set the date and time for 12/01/2008 at 5:00 pm (17:00). Set the view to Horizon to Zenith under Options and look to the South-West (SW). What you will see is a conjunction of the Moon, Jupiter, and Venus. (a) Are these objects all in a line as seen from the Earth? (b) How long will the Moon be a part of the conjunction in days? (c) How long will Venus and Jupiter both be near the constellation Sagittarius? (d) When does Venus enter Capricornus?
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Part III: Motion of the Planets in the Sky

  1. Go to the Sky tab. Set the date for 1/1/2008. Using the Full Sky - Flat viewing option find out when Venus is visible in the sky. Try advancing time by hours starting at 00:00 (midnight). You can only see a planet if it is above the horizon and if the Sun is not above the horizon. Fill in the following table:
    Date Venus-Rise Venus-Set Time of Day
    Venus is Visible     		Direction to Look
    12/1/2008        
    1/1/2009        
    2/1/2009        
    3/1/2009        
    4/1/2009        
    5/1/2009        
    6/1/2009        
  2. Venus is often called the Morning Star. Sometimes it is called the Evening Star. Venus is a planet but all bright and distant objects look like stars in the sky. What do these terms really mean?
    Morning Star:

    Evening Star

  3. When during the times you explored is Venus a Morning Star? When is it an Evening Star?
  4. When will Venus be a Morning Star again? When will it be an Evening Star again after that?
  5. Go to the Ecliptic tab. This tab shows the plane of the Earth’s orbit projected on the sky. It only shows the constellations of the Zodiac which are the constellations where you will always find the Sun, Moon and planets. Set the date for 10/01/07 and note the location of Mars in the upper part of the view window. Use the arrow keys to move forward by days and watch the motion of Mars against the background stars (in this case, the constellation Gemini). Describe how Mars’s location changes from 10/01/07 through 5/01/08. Draw a picture showing the bright stars of Gemini and sketch a track showing how Mars’s location changed.
  6. Go to the Orbits tab and watch the motion of the planet Mars for the same date range: from 10/01/07 through 05/01/08 (use the arrow keys to change the day). What is its real motion through space? Watch it again and this time watch how Earth moves at the same time. Why does Mars move so strangely relative to the background stars when viewed from Earth? For help with this, see http://en.wikipedia.org/wiki/Retrograde_motion.
  7. Use the Orbits tab to watch the same date range again but this time change Center on Sun to Center on Earth in the Options section. How does Mars appear to move through space now? This is the problem ancient astronomers had, for example Ptolemy. Since they didn’t know that the Earth was moving the model they made of the Solar System was more like the one you see here.





Part IV: Motions in the Sky and in their Orbits

 

  1. Find the menu just to the right of the place where you set the time and date. Underneath these menus it says “previous/next event”. On the left menu scroll down until you reach the word Opposition. On the right menu it will probably automatically choose Mars. Click the blue arrow to the left to go to the most recent time that the planet Mars was at Opposition. (You will soon learn what this means). What is the time and date of the most recent Opposition of Mars?
  2. Click on the tab near the top of the display window where it says Orbits. This will show you the solar system at the time and date selected by using the event menu. Play with the options in the lower-right corner of the screen to see what you can do on this tab. Leave the time and date at the recent Opposition of Mars. When you are done playing set the options back to Out to Mars only, Center on Sun, and Distance in AU. Draw a picture of the relative location of the Sun, Mars, and the Earth.
    What do you notice about the locations of Mars, the Sun, and the Earth?
  3. Hit the Now button again to reset the time and date. Use the events menu to choose the next Opposition of Jupiter. What is the time and date of this Opposition?
  4. Draw the relative locations of the Sun, the Earth and Jupiter at the Opposition of Jupiter.
    What do you notice about the locations of Jupiter, the Sun, and the Earth?
  5. Go to the next Opposition for each of the remaining planets (Saturn, Uranus, Neptune and Pluto). Report the date and time of each Opposition for each planet starting from today’s date. Draw pictures showing the locations of the Sun, the planet in question and the Earth for each Opposition.
    Planet Opposition
    Date    		 Opposition
    Time
    Saturn    
    Uranus    
    Neptune    
    Pluto    
  6. Using your best writing explain what is meant by the word Opposition in planetary astronomy. You will need to write several (3 - 4) sentences to do this completely.
  7. Use similar techniques to report all of the Superior Conjunctions (Sup. Conj. in the events menu) for all of the available planets. What are the times and dates for each one? Draw the Sun, the relevant planet, and the Earth for each one.
    Planet Superior Conjunction
    Date    		 Superior Conjunction
    Time
    Mercury    
    Venus    
    Mars    
    Jupiter    
    Saturn    
    Uranus    
    Neptune    
    Pluto    
  8. Using your best writing explain what is meant by the Superior Conjunction in planetary astronomy. You will need to write several (3 - 4) sentences to do this completely.
  9. Use similar techniques to report all of the Inferior Conjunctions (Inf. Conj. in the events menu) for all of the available planets. What are the times and dates for each one (make a table)? Draw the Sun, the relevant planet, and the Earth for each one.
  10. Using your best writing explain what is meant by the Inferior Conjunction in planetary astronomy. You will need to write several (3 - 4) sentences to do this completely.
  11. The planets available for calculating an Inferior Conjunction are limited? Why?
  12. What time of day do planets in (a) Opposition rise in the E? (b) And planets in Superior Conjunction? (c) And planets in Inferior Conjunction? (Hint: Set SkyViewCafé to Opposition for Mars, then check the sky screen to find out when it rises. Then do the same for Superior Conjunction. Then use Venus for Inferior Conjunction.
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Last updated: Dec 07, 2008       Home