JUPITER – Appearance, Features, and Rotation

(This observing exercise is geared for middle and high school students.)


The appearance of Jupiter through a telescope is stunning and spectacular. The planet has a large disk with dark belts and light zones, and sometimes the Great Red Spot can be seen. Given that its rotation rate is just under 10 hours, it does not take long to notice. In attention, it is often surrounded by four large moons, whose orbital periods range from 2 to 17 days. These moons, from inner- to outer-most are Io, Europa, Ganymede, and Callisto. Sometimes one is not seen, though, because it is either in front of or behind Jupiter.



1. When viewing Jupiter, does it look like a solid surface or the upper layers of an atmosphere? What kind of observations would help distinguish between the two possibilities?


2. The color of Jupiter is not uniform. It has bright lateral zones and dark bands. Are these related to Jupiter's rotation?


3. Is the Great Red Spot visible? How can it be used to determine the rotation rate of Jupiter?


4. What is the shape of Jupiter. Is it really a circle? How can this “deformity” be explained?


5. How many moons can be counted? Which ones are they?


6. Explain why (a) all of the planets revolve around the Sun in one direction (i.e., counterclockwise as seen from above the Sun's north pole); (b) most of the planets revolve counterclockwise; and (c) most of the moons revolve in a counterclockwise direction around their respective planet.



1. Compute the degree of flattening.


Oblateness  =  (Diameter_long – Diameter_short) / Diameter_long  =  ____________________


2. Compute the angular and linear size of the Great Red Spot.


Angular diameter  =  Diameter_RedSpot / Diameter_Jupiter x 180°  =  ____________________

Linear diameter  =  Diameter_RedSpot / Diameter_Jupiter x 142,800 km  =  ____________________


3. Compute the rotation rate of Jupiter using the Great Red Spot.


Diameter of Jupiter  =  140,000 km

Initial Position  =  ___________________________

Initial Time       =  ___________________________

Final Position  =  ___________________________

Final Time       =  ___________________________


Position Change  = Final Position – Initial Position  =  ____________________

Linear Change  = Position Change / Diameter of Jupiter  =  ____________________

Time Change  = Final Time – Initial Time  =  ____________________

Rotation Rate  = ( Linear Change / Time Change ) x 2  =  ____________________


4. Compute the distance from Jupiter to the Earth in AU's, km, miles, and light-travel time (in minutes). Assume Jupiter is at its nearest point to the Earth.


Earth-Sun Distance  =  1.0 AU

Jupiter-Sun Distance  =  5.2 AU

Jupiter-Earth Distance  =  5.2 – 1.0 = 4.2 AU

Jupiter-Earth Distance  =  ____________________ km

Jupiter-Earth Distance  =  ____________________ miles

Light Travel Time  =  ____________________ minutes



James Sowell, 2013