Jupiter Observations.

Jupiter – king of the gods. Jupiter is the largest, and by far the most massive planet in the solar system. You could fit 11 Earths across it, and more than 1000 Earths inside it! It rotates the fastest and has the most turbulent atmosphere of any planet. One of its storm systems, called The Great Red Spot, is twice the size of Earth and has lasted more than 300 years! Jupiter does not have a solid surface. Rather, as one sinks lower in the atmosphere, the pressure rises and the gas gets increasingly dense until it gradually turns liquid. There is no sharp boundary between the gas and liquid regions. At increasing depths, the liquid eventually turns solid from the enormous pressure of all of the mass above. Jupiter is the second most oblate ("squashed") planet due to its rapid rotation. It also has a collection of four large moons, called the Galilean satellites after their discoverer. Two of these satellites are larger than the planet Mercury.

Objective:

To observe and map the atmospheric features of Jupiter, observe its rotation, and identify the Galilean satellites.

Requirements:

Two detailed sketches of the Jupiter made at least 1 hour apart.

Two low-power sketches of the Galilean satellite system made at least two days apart.

Directions:

1. Set up a telescope and align it with the north celestial pole. An accurate alignment is not required.

2. Find Jupiter. Make a sketch of the planet and the Galilean satellites at low power. Be careful to make an accurate sketch, using the diameter of Jupiter as a measuring guide. Identify them based upon the following: Io is yellow-orange and is usually the closest satellite. Europa is the second closest satellite to Jupiter, is the faintest, and is white in color. Ganymede is next, is yellowish, and is the brightest. Callisto is the farthest of the Galilean moons and is bluish grey.

3. Switch to high power.

4. Make an outline sketch of Jupiter, and note its oblateness. Shade the ball of the planet a neutral gray so that light features can be sketched by erasing, and dark features can be sketched by drawing darker.

5. Observe Jupiter (without sketching) for about five minutes to let your eyes adapt to the subtle details on the surface of the planet, and look to see if you can resolve the Galilean satellites as disks. Can you tell which one is largest? Smallest?

6. Quickly sketch in the MAJOR details that you see on the surface.

7. Fill out the observing form (time, date, magnification, weather, seeing, etc.)

8. Now carefully fill in all of the tiny details that you can glimpse. Make notes of interesting features you see. Even the tiniest detail that you are sure of should be included. Be sure to record colors of the cloud features and the moons. Also look for and accurately sketch the oblateness of Jupiter. If you cannot identify small cloud features, it will be very difficult to detect the rotation of the planet.

9. Wait at least an hour and make another sketch, try to identify features from the first sketch that have shifted. Identify which direction Jupiter is rotating.

10. Make a second, low-power sketch of the Galilean satellites at least two days later. Go to the library and find a Galilean satellite diagram in a Sky & Telescope or Astronomy magazine. Use this diagram to conclusively identify the satellites in your two low-power sketches. Include a copy of this diagram in you lab report.

Questions:

1. What is the orbital period of Jupiter? How far is Jupiter’s rotational axis inclined to its orbital plane? (Earth is inclined 23.5 degrees for comparison) Does Jupiter have seasons?  What evidence do you have from your observations regarding the inclination of Jupiter's rotational axis?

2. What is the rotational period of Jupiter? About how many degrees does Jupiter rotate in an hour? Did you detect any rotation?

3. What color was the planet? What are the belts and zones?  What causes their colors?

4. Compare the colors of Io and Europa that you observed with their actual colors. What causes the colors of Io and Europa (consult a text).  

5.  Could you resolve any of the Galilean satellites as disks instead of just points of light? Which one looked largest?  

6. Identify which satellite was which from the satellite diagrams that you obtained from the magazines, as described above.  Include a copy of the diagram and clearly mark the time of your observations on them.  Describe how you read the diagram and compare your identifications from the diagram with those that you made at the telescope.  Explain any discrepancies.

7. How oblate is Jupiter? To answer this question, measure the ratio of equatorial/polar diameters from your sketch.  Divide the equatorial diameter by the polar diameter and provide that number. Show your work.  How does your number compare with the real oblateness of Jupiter?  To perform this comparison, find the equatorial and polar diameters of Jupiter and divide the two and compare with the same ratio that you obtained from your sketches.