Activity:
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. (apparent) retrograde motion:
4. astronomical unit (AU):
5. eccentricity:
6. orbital inclination:

7. orbital period:
8. rotational period:
9. terrestrial planet:
10. Jovian planet:
11. dwarf planet:
12. asteroid:

Next, choose one of the following Solar System objects to investigate: Mercury, Venus, Earth, the Moon, Mars, Asteroids, Jupiter, Saturn, Uranus, Neptune, Pluto, or Comets.Use the list on Wikipedia found on the List of Solar System Objects page. Find and record the following information about your solar system object:

1. aphelion distance:
   and
   
   perihelion distance:
2. length of day:
3. length of year:
4. eccentricity:

5. mass:
6. composition:
7. size relative to earth:
8. space probe visits (name & date):

9. special features (find five that make it unique):
10. 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?
11. 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. 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.
5. Set the time and date to -1952-03-02 06:30 on the Sky tab of SkyViewCafé. Rotate the view to look due south-east (SE) and set the view options to Horizon to Zenith. Draw what you see in the sky in one half of the space below. In the other half draw what you see on the Orbits tab when you set the viewing angle to 0° and select Out to Saturn under Options.
6. What is a planetary conjunction?

Oppositions, Superior Conjunctions, and Inferior Conjunctions

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:

5. 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?
6. 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?
7. 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?
8. 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?

9. 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.
10. 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 orbit of a planet, a planet, and the Earth and Earth’s orbit showing what all superior conjunctions have in common.

    Planet	Superior Conjunction Date	Superior Conjunction Time
    Mercury
    Venus
    Mars
    Jupiter

11. Using your best writing explain what is meant by the Superior Conjunction in planetary astronomy.
12. Use similar techniques to report all of the Inferior Conjunctions (Inf. Conj. in the events menu) for all of the available planets. Draw the Sun, the orbit of a planet, a planet, and the Earth and Earth’s orbit showing what all inferior conjunctions have in common.

    Planet	Inferior Conjunction Date	Inferior Conjunction Time
    Mercury
    Venus

13. Using your best writing explain what is meant by the Inferior Conjunction in planetary astronomy.
14. The planets available for calculating an Inferior Conjunction are limited? Why?